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Bibliography on: Horizontal Gene Transfer

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ESP: PubMed Auto Bibliography 29 Sep 2023 at 01:30 Created: 

Horizontal Gene Transfer

The pathology-inducing genes of O157:H7 appear to have been acquired, likely via prophage, by a nonpathogenic E. coli ancestor, perhaps 20,000 years ago. That is, horizontal gene transfer (HGT) can lead to the profound phenotypic change from benign commensal to lethal pathogen. "Horizontal" in this context refers to the lateral or "sideways" movement of genes between microbes via mechanisms not directly associated with reproduction. HGT among prokaryotes can occur between members of the same "species" as well as between microbes separated by vast taxonomic distances. As such, much prokaryotic genetic diversity is both created and sustained by high levels of HGT. Although HGT can occur for genes in the core-genome component of a pan-genome, it occurs much more frequently among genes in the optional, flex-genome component. In some cases, HGT has become so common that it is possible to think of some "floating" genes more as attributes of the environment in which they are useful rather than as attributes of any individual bacterium or strain or "species" that happens to carry them. For example, bacterial plasmids that occur in hospitals are capable of conferring pathogenicity on any bacterium that successfully takes them up. This kind of genetic exchange can occur between widely unrelated taxa.

Created with PubMed® Query: ( "horizontal gene transfer" OR "lateral gene transfer") NOT pmcbook NOT ispreviousversion

Citations The Papers (from PubMed®)


RevDate: 2023-09-28

Li L, Liu Z, Meng D, et al (2023)

Sequence similarity network and protein structure prediction offer insights into the evolution of microbial pathways for ferrous iron oxidation.

mSystems [Epub ahead of print].

Dissimilatory ferrous iron [Fe(II)] oxidation is a well-established microbial energy generation strategy. This study aims to comprehensively investigate the distribution and evolution of recognized Fe(II) oxidation pathways through comparative analysis. Interestingly, we have discovered a wide range of taxonomic groups that harbor homologs to known Fe(II) oxidation proteins. The presence of these homologs among phylogenetically distant lineages and their frequent association with mobile genetic elements strongly suggest horizontal gene transfer events involving Fe(II) oxidation proteins, such as the rus operon of Acidithiobacillus and Cyc572 from Leptospirillum lineages belonging to classes Gammaproteobacteria and Betaproteobacteria often present at the hub positions of the protein sequence similarity networks from which homologs of other taxa are derived. In addition, RoseTTAFold predictions have provided valuable insights into the structural characteristics of previously unknown Fe(II) oxidation components. Despite having limited sequence identity, a significant number of acknowledged proteins involved in different Fe(II) oxidation pathways exhibit close structural similarities, including Cyc2 and Cyc572. Collectively, this study significantly enhances our understanding of the distribution and evolution of microbial ferrous iron oxidation pathways. IMPORTANCE Microbial Fe(II) oxidation is a crucial process that harnesses and converts the energy available in Fe, contributing significantly to global element cycling. However, there are still many aspects of this process that remain unexplored. In this study, we utilized a combination of comparative genomics, sequence similarity network analysis, and artificial intelligence-driven structure modeling methods to address the lack of structural information on Fe(II) oxidation proteins and offer a comprehensive perspective on the evolution of Fe(II) oxidation pathways. Our findings suggest that several microbial Fe(II) oxidation pathways currently known may have originated within classes Gammaproteobacteria and Betaproteobacteria.

RevDate: 2023-09-28

Iasakov T (2023)

Evolution End Classification of tfd Gene Clusters Mediating Bacterial Degradation of 2,4-Dichlorophenoxyacetic Acid (2,4-D).

International journal of molecular sciences, 24(18): pii:ijms241814370.

The tfd (tfdI and tfdII) are gene clusters originally discovered in plasmid pJP4 which are involved in the bacterial degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) via the ortho-cleavage pathway of chlorinated catechols. They share this activity, with respect to substituted catechols, with clusters tcb and clc. Although great effort has been devoted over nearly forty years to exploring the structural diversity of these clusters, their evolution has been poorly resolved to date, and their classification is clearly obsolete. Employing comparative genomic and phylogenetic approaches has revealed that all tfd clusters can be classified as one of four different types. The following four-type classification and new nomenclature are proposed: tfdI, tfdII, tfdIII and tfdIV(A,B,C). Horizontal gene transfer between Burkholderiales and Sphingomonadales provides phenomenal linkage between tfdI, tfdII, tfdIII and tfdIV type clusters and their mosaic nature. It is hypothesized that the evolution of tfd gene clusters proceeded within first (tcb, clc and tfdI), second (tfdII and tfdIII) and third (tfdIV(A,B,C)) evolutionary lineages, in each of which, the genes were clustered in specific combinations. Their clustering is discussed through the prism of hot spots and driving forces of various models, theories, and hypotheses of cluster and operon formation. Two hypotheses about series of gene deletions and displacements are also proposed to explain the structural variations across members of clusters tfdII and tfdIII, respectively. Taking everything into account, these findings reconstruct the phylogeny of tfd clusters, have delineated their evolutionary trajectories, and allow the contribution of various evolutionary processes to be assessed.

RevDate: 2023-09-28

Xia X (2023)

Horizontal Gene Transfer and Drug Resistance Involving Mycobacterium tuberculosis.

Antibiotics (Basel, Switzerland), 12(9): pii:antibiotics12091367.

Mycobacterium tuberculosis (Mtb) acquires drug resistance at a rate comparable to that of bacterial pathogens that replicate much faster and have a higher mutation rate. One explanation for this rapid acquisition of drug resistance in Mtb is that drug resistance may evolve in other fast-replicating mycobacteria and then be transferred to Mtb through horizontal gene transfer (HGT). This paper aims to address three questions. First, does HGT occur between Mtb and other mycobacterial species? Second, what genes after HGT tend to survive in the recipient genome? Third, does HGT contribute to antibiotic resistance in Mtb? I present a conceptual framework for detecting HGT and analyze 39 ribosomal protein genes, 23S and 16S ribosomal RNA genes, as well as several genes targeted by antibiotics against Mtb, from 43 genomes representing all major groups within Mycobacterium. I also included mgtC and the insertion sequence IS6110 that were previously reported to be involved in HGT. The insertion sequence IS6110 shows clearly that the Mtb complex participates in HGT. However, the horizontal transferability of genes depends on gene function, as was previously hypothesized. HGT is not observed in functionally important genes such as ribosomal protein genes, rRNA genes, and other genes chosen as drug targets. This pattern can be explained by differential selection against functionally important and unimportant genes after HGT. Functionally unimportant genes such as IS6110 are not strongly selected against, so HGT events involving such genes are visible. For functionally important genes, a horizontally transferred diverged homologue from a different species may not work as well as the native counterpart, so the HGT event involving such genes is strongly selected against and eliminated, rendering them invisible to us. In short, while HGT involving the Mtb complex occurs, antibiotic resistance in the Mtb complex arose from mutations in those drug-targeted genes within the Mtb complex and was not gained through HGT.

RevDate: 2023-09-28

Al-Sarawi HA, Habibi N, Uddin S, et al (2023)

Antibiotic Resistance Mediated by Escherichia coli in Kuwait Marine Environment as Revealed through Genomic Analysis.

Antibiotics (Basel, Switzerland), 12(9): pii:antibiotics12091366.

Antibiotic-resistance gene elements (ARGEs) such as antibiotic-resistance genes (ARGs), integrons, and plasmids are key to the spread of antimicrobial resistance (AMR) in marine environments. Kuwait's marine area is vulnerable to sewage contaminants introduced by numerous storm outlets and indiscriminate waste disposal near recreational beaches. Therefore, it has become a significant public health issue and warrants immediate investigation. Coliforms, especially Gram-negative Escherichia coli, have been regarded as significant indicators of recent fecal pollution and carriers of ARGEs. In this study, we applied a genome-based approach to identify ARGs' prevalence in E. coli isolated from mollusks and coastal water samples collected in a previous study. In addition, we investigated the plasmids and intl1 (class 1 integron) genes coupled with the ARGs, mediating their spread within the Kuwait marine area. Whole-genome sequencing (WGS) identified genes resistant to the drug classes of beta-lactams (blaCMY-150, blaCMY-42, blaCTX-M-15, blaDHA-1, blaMIR-1, blaOKP-B-15, blaOXA-1, blaOXA-48, blaTEM-1B, blaTEM-35), trimethoprim (dfrA14, dfrA15, dfrA16, dfrA1, dfrA5, dfrA7), fluroquinolone (oqxA, oqxB, qnrB38, qnrB4, qnrS1), aminoglycoside (aadA2, ant(3'')-Ia, aph(3'')-Ib, aph(3')-Ia, aph(6)-Id), fosfomycin (fosA7, fosA_6, fosA, fosB1), sulfonamide (sul1, sul2, sul3), tetracycline (tet-A, tet-B), and macrolide (mph-A). The MFS-type drug efflux gene mdf-A is also quite common in E. coli isolates (80%). The plasmid ColRNAI was also found to be prevalent in E. coli. The integron gene intI1 and gene cassettes (GC) were reported to be in 36% and 33%, respectively, of total E. coli isolates. A positive and significant (p < 0.001) correlation was observed between phenotypic AMR-intl1 (r = 0.311) and phenotypic AMR-GC (r = 0.188). These findings are useful for the surveillance of horizontal gene transfer of AMR in the marine environments of Kuwait.

RevDate: 2023-09-28

Li J, C Cullis (2023)

Comparative Analysis of Tylosema esculentum Mitochondrial DNA Revealed Two Distinct Genome Structures.

Biology, 12(9): pii:biology12091244.

Tylosema esculentum, commonly known as the marama bean, is an underutilized legume with nutritious seeds, holding potential to enhance food security in southern Africa due to its resilience to prolonged drought and heat. To promote the selection of this agronomically valuable germplasm, this study assembled and compared the mitogenomes of 84 marama individuals, identifying variations in genome structure, single-nucleotide polymorphisms (SNPs), insertions/deletions (indels), heteroplasmy, and horizontal transfer. Two distinct germplasms were identified, and a novel mitogenome structure consisting of three circular molecules and one long linear chromosome was discovered. The structural variation led to an increased copy number of specific genes, nad5, nad9, rrnS, rrn5, trnC, and trnfM. The two mitogenomes also exhibited differences at 230 loci, with only one notable nonsynonymous substitution in the matR gene. Heteroplasmy was concentrated at certain loci on chromosome LS1 (OK638188). Moreover, the marama mitogenome contained an over 9 kb insertion of cpDNA, originating from chloroplast genomes, but had accumulated mutations and lost gene functionality. The evolutionary and comparative genomics analysis indicated that mitogenome divergence in marama might not be solely constrained by geographical factors. Additionally, marama, as a member from the Cercidoideae subfamily, tends to possess a more complete set of mitochondrial genes than Faboideae legumes.

RevDate: 2023-09-28

Hafez M, Gourlie R, McDonald M, et al (2023)

Evolution of the ToxB gene in Pyrenophora tritici-repentis and related species.

Molecular plant-microbe interactions : MPMI [Epub ahead of print].

Pyrenophora tritici-repentis is a destructive pathogen of wheat with global impact. It possesses a highly plastic open pangenome shaped by the gain and loss of effector genes. This study investigated the allelic variations in the chlorosis-encoding gene, ToxB, across 422 isolates representing all identified pathotypes and worldwide origins. To gain better insights into ToxB evolution, we examined its presence and variability in other Pyrenophora spp. A ToxB haplotype network was constructed, revealing the evolutionary relationships of this gene (20 haplotypes) across four Pyrenophora species. Notably, toxb, the homolog of ToxB, was detected for the first time in the barley pathogen Pyrenophora teres. The ToxB/toxb genes display evidence of selection that is characterized by loss of function, duplication, and diverse mutations. Among ToxB/toxb open reading frame, 72 mutations were identified, including 14 synonymous, 55 nonsynonymous, and 3 indel mutations. Remarkably, a ~5.6 Kb Copia-like retrotransposon, named Copia-1_Ptr, was found inserted in the toxb gene of a race 3 isolate. This insert disrupted the ToxB gene's function, a first case of effector gene disruption by a transposable element in Ptr. Additionally, a microsatellite with 25-nucleotide repeats (0 to 10) in the upstream region of ToxB suggested a potential mechanism influencing ToxB expression and regulation. Exploring ToxB-like protein distribution in other Ascomycetes revealed their presence in 19 additional species, including the Leotiomycetes class for the first time. The presence/absence pattern of ToxB-like proteins defied species relatedness compared to a phylogenetic tree, suggesting a past horizontal gene transfer event.

RevDate: 2023-09-27

Sharma M, Singh DN, Uttam G, et al (2023)

Adaptive evolution of Sphingopyxis sp. MC4 conferred degradation potential for persistent β- and δ-Hexachlorocyclohexane (HCH) isomers.

Journal of hazardous materials, 461:132545 pii:S0304-3894(23)01828-9 [Epub ahead of print].

Hexachlorocyclohexane (HCH), an organochlorine pesticide imposes several harmful impacts on the ecosystem. β- and δ-isomers of HCH are highly toxic, persistent, and recalcitrant to biodegradation, slow and incomplete degradation of β- and δ- isomers have been reported in a few strains. We have isolated a strain designated as Sphingopyxis strain MC4 that can tolerate and degrade high concentrations of α-, β-, γ- and δ-HCH isomers. To date, no other Sphingopyxis strain has been reported to degrade β- and δ-isomers. To understand the underlying genetic makeup contributing to adaptations, the whole genome of strain MC4 was sequenced. Comparative genome analysis showed that strain MC4 harbors the complete pathway (lin genes) required for HCH degradation. Genetic footprints such as presence of lin genes on genomic islands, IS6100 elements in close proximity of lin genes, and synteny in lin flanking regions with other strains reflects the horizontal gene transfer in strain MC4. Positive selection and HGT drive the adaptive evolution of strain MC4 under the pressure of HCH contamination that it experienced in its surrounding niche. In silico analyses showed efficient binding of β- and δ-isomers with enzymes leading to rapid degradation that need further validation by cloning and biochemical experiments.

RevDate: 2023-09-27

Shikov AE, Savina IA, Nizhnikov AA, et al (2023)

Recombination in Bacterial Genomes: Evolutionary Trends.

Toxins, 15(9): pii:toxins15090568.

Bacterial organisms have undergone homologous recombination (HR) and horizontal gene transfer (HGT) multiple times during their history. These processes could increase fitness to new environments, cause specialization, the emergence of new species, and changes in virulence. Therefore, comprehensive knowledge of the impact and intensity of genetic exchanges and the location of recombination hotspots on the genome is necessary for understanding the dynamics of adaptation to various conditions. To this end, we aimed to characterize the functional impact and genomic context of computationally detected recombination events by analyzing genomic studies of any bacterial species, for which events have been detected in the last 30 years. Genomic loci where the transfer of DNA was detected pertained to mobile genetic elements (MGEs) housing genes that code for proteins engaged in distinct cellular processes, such as secretion systems, toxins, infection effectors, biosynthesis enzymes, etc. We found that all inferences fall into three main lifestyle categories, namely, ecological diversification, pathogenesis, and symbiosis. The latter primarily exhibits ancestral events, thus, possibly indicating that adaptation appears to be governed by similar recombination-dependent mechanisms.

RevDate: 2023-09-27

Ma J, Zhao H, Mo S, et al (2023)

Acquisition of Type I methyltransferase via horizontal gene transfer increases the drug resistance of Aeromonas veronii.

Microbial genomics, 9(9):.

Aeromonas veronii is an opportunistic pathogen that affects both fish and mammals, including humans, leading to bacteraemia, sepsis, meningitis and even death. The increasing virulence and drug resistance of A. veronii are of significant concern and pose a severe risk to public safety. The Type I restriction-modification (RM) system, which functions as a bacterial defence mechanism, can influence gene expression through DNA methylation. However, little research has been conducted to explore its origin, evolutionary path, and relationship to virulence and drug resistance in A. veronii. In this study, we analysed the pan-genome of 233 A. veronii strains, and the results indicated that it was 'open', meaning that A. veronii has acquired additional genes from other species. This suggested that A. veronii had the potential to adapt and evolve rapidly, which might have contributed to its drug resistance. One Type I methyltransferase (MTase) and two complete Type I RM systems were identified, namely AveC4I, AveC4II and AveC4III in A. veronii strain C4, respectively. Notably, AveC4I was exclusive to A. veronii C4. Phylogenetic analysis revealed that AveC4I was derived from horizontal gene transfer from Thiocystis violascens and exchanged genes with the human pathogen Comamonas kerstersii. Single molecule real-time sequencing was applied to identify the motif methylated by AveC4I, which was unique and not recognized by any reported MTases in the REBASE database. We also annotated the functions and pathways of the genes containing the motif, revealing that AveC4I may control drug resistance in A. veronii C4. Our findings provide new insight on the mechanisms underlying drug resistance in pathogenic bacteria. By identifying the specific genes and pathways affected by AveC4I, this study may aid in the development of new therapeutic approaches to combat A. veronii infections.

RevDate: 2023-09-27

Tekle YI, Tran H, Wang F, et al (2023)

Omics of an Enigmatic Marine Amoeba Uncovers Unprecedented Gene Trafficking from Giant Viruses and Provides Insights into Its Complex Life Cycle.

Microbiology research, 14(2):656-672.

Amoebozoa include lineages of diverse ecology, behavior, and morphology. They are assumed to encompass members with the largest genome sizes of all living things, yet genomic studies in the group are limited. Trichosphaerium, a polymorphic, multinucleate, marine amoeba with a complicated life cycle, has puzzled experts for over a century. In an effort to explore the genomic diversity and investigate extraordinary behavior observed among the Amoebozoa, we used integrated omics approaches to study this enigmatic marine amoeba. Omics data, including single-cell transcriptomics and cytological data, demonstrate that Trichosphaerium sp. possesses the complete meiosis toolkit genes. These genes are expressed in life stages of the amoeba including medium and large cells. The life cycle of Trichosphaerium sp. involves asexual processes via binary fission and multiple fragmentation of giant cells, as well as sexual-like processes involving genes implicated in sexual reproduction and polyploidization. These findings are in stark contrast to a life cycle previously reported for this amoeba. Despite the extreme morphological plasticity observed in Trichosphaerium, our genomic data showed that populations maintain a species-level intragenomic variation. A draft genome of Trichosphaerium indicates elevated lateral gene transfer (LGT) from bacteria and giant viruses. Gene trafficking in Trichosphaerium is the highest within Amoebozoa and among the highest in microbial eukaryotes.

RevDate: 2023-09-26

Liu H, Shi B, Liu W, et al (2023)

Effects of magnesium-modified biochar on antibiotic resistance genes and microbial communities in chicken manure composting.

Environmental science and pollution research international [Epub ahead of print].

Abatement of antibiotic resistance genes (ARGs) in livestock manure by composting has attracted attention. This study investigated the effect of adding magnesium-modified biochar (MBC) on ARGs and microbial communities in chicken manure composting. Twelve genes for tetracyclines, sulfonamides, and macrolides, and mobile genetic elements were measured in the compost pile. The results showed that after 45 days of the composting, the treatment groups of MBC had longer high temperature periods, significantly higher germination indices (GI) and lower phytotoxicity. There were four major dominant phyla (Firmicutes, Actinobacteriota, Proteobacteria, and Bacteroidota) in the compost. The abundance of Firmicutes decreased significantly during the compost cooling period; tetracycline resistance genes demonstrated an extremely significant positive correlation with Firmicutes, showing a trend of the same increase and decrease with composting time; tetT, tetO, tetM, tetW, ermB, and intI2 were reduced in the MBC group; the total abundance of resistance genes in the 2% MBC addition group was 0.67 times that of the control; Proteobacteria and Chloroflexi were also significantly lower than the other treatment groups. Most ARGs were significantly associated with mobile genetic elements (MGEs); MBC can reduce the spread and diffusion of ARGs by reducing the abundance of MGEs and inhibiting horizontal gene transfer (HGT).

RevDate: 2023-09-25

Gao J, Xing X, Cai W, et al (2023)

Effect of micropollutants on disinfection byproducts and antibiotic resistance genes in drinking water in the process of biological activated carbon treatment.

Journal of hazardous materials, 461:132304 pii:S0304-3894(23)01587-X [Epub ahead of print].

The biofilm stress response of biological activated carbon (BAC) was investigated under prolonged exposure to sulfadiazine and 2,4-Dichlorophenoxyacetic acid, simulating complex emerging organic contaminants (EOCs) that are mainly involved in the formation of nitrogenous disinfection byproducts (N-DBPs) and antibiotic resistance genes (ARGs). Under trace complex EOCs condition (2 µg/L), N-DBP precursors and abundance of ARGs increased significantly in BAC effluent. The total formation potential of haloacetonitriles (HANs) and halonitromethanes (HNMs) was 751.47 ± 2.98 ng/L, which was much higher than the control group (440.67 ± 13.38 ng/L without EOCs). Similarly, the relative abundance of ARGs was more than twice that in the control group. The complex EOCs induce excessive extracellular polymeric substance secretion (EPS), thereby causing more N-DBP precursors and stronger horizontal gene transfer. Metagenome analysis revealed that functional amino acid and protein biosynthesis genes were overexpressed compared to the control group, causing more EPS to be secreted into the external environment. Complex EOCs promote Cobetia, Clostridium, and Streptomyces dominance, contributing to the production of N-DBP precursors and ARGs. For the first time, in addition to the direct hazards of the EOCs, this study successfully revealed the indirect water quality risks of complex EOCs from the microbial stress response during BAC treatment. Synergistic regulation of EOCs and microorganisms is important for tap water security.

RevDate: 2023-09-25

Schalamun M, M Schmoll (2022)

Trichoderma - genomes and genomics as treasure troves for research towards biology, biotechnology and agriculture.

Frontiers in fungal biology, 3:1002161.

The genus Trichoderma is among the best studied groups of filamentous fungi, largely because of its high relevance in applications from agriculture to enzyme biosynthesis to biofuel production. However, the physiological competences of these fungi, that led to these beneficial applications are intriguing also from a scientific and ecological point of view. This review therefore summarizes recent developments in studies of fungal genomes, updates on previously started genome annotation efforts and novel discoveries as well as efforts towards bioprospecting for enzymes and bioactive compounds such as cellulases, enzymes degrading xenobiotics and metabolites with potential pharmaceutical value. Thereby insights are provided into genomes, mitochondrial genomes and genomes of mycoviruses of Trichoderma strains relevant for enzyme production, biocontrol and mycoremediation. In several cases, production of bioactive compounds could be associated with responsible genes or clusters and bioremediation capabilities could be supported or predicted using genome information. Insights into evolution of the genus Trichoderma revealed large scale horizontal gene transfer, predominantly of CAZyme genes, but also secondary metabolite clusters. Investigation of sexual development showed that Trichoderma species are competent of repeat induced point mutation (RIP) and in some cases, segmental aneuploidy was observed. Some random mutants finally gave away their crucial mutations like T. reesei QM9978 and QM9136 and the fertility defect of QM6a was traced back to its gene defect. The Trichoderma core genome was narrowed down to 7000 genes and gene clustering was investigated in the genomes of multiple species. Finally, recent developments in application of CRISPR/Cas9 in Trichoderma, cloning and expression strategies for the workhorse T. reesei as well as the use genome mining tools for bioprospecting Trichoderma are highlighted. The intriguing new findings on evolution, genomics and physiology highlight emerging trends and illustrate worthwhile perspectives in diverse fields of research with Trichoderma.

RevDate: 2023-09-25

Gonçalves C, Harrison MC, Steenwyk JL, et al (2023)

Diverse signatures of convergent evolution in cacti-associated yeasts.

bioRxiv : the preprint server for biology pii:2023.09.14.557833.

Many distantly related organisms have convergently evolved traits and lifestyles that enable them to live in similar ecological environments. However, the extent of phenotypic convergence evolving through the same or distinct genetic trajectories remains an open question. Here, we leverage a comprehensive dataset of genomic and phenotypic data from 1,049 yeast species in the subphylum Saccharomycotina (Kingdom Fungi, Phylum Ascomycota) to explore signatures of convergent evolution in cactophilic yeasts, ecological specialists associated with cacti. We inferred that the ecological association of yeasts with cacti arose independently ∼17 times. Using machine-learning, we further found that cactophily can be predicted with 76% accuracy from functional genomic and phenotypic data. The most informative feature for predicting cactophily was thermotolerance, which is likely associated with duplication and altered evolutionary rates of genes impacting the cell envelope in several cactophilic lineages. We also identified horizontal gene transfer and duplication events of plant cell wall-degrading enzymes in distantly related cactophilic clades, suggesting that putatively adaptive traits evolved through disparate molecular mechanisms. Remarkably, multiple cactophilic lineages and their close relatives are emerging human opportunistic pathogens, suggesting that the cactophilic lifestyle-and perhaps more generally lifestyles favoring thermotolerance-may preadapt yeasts to cause human disease. This work underscores the potential of a multifaceted approach involving high throughput genomic and phenotypic data to shed light onto ecological adaptation and highlights how convergent evolution to wild environments could facilitate the transition to human pathogenicity.

RevDate: 2023-09-25

Palanisamy V, Bosilevac JM, Barkhouse DA, et al (2023)

Shotgun-metagenomics reveals a highly diverse and communal microbial network present in the drains of three beef-processing plants.

Frontiers in cellular and infection microbiology, 13:1240138.

BACKGROUND: Multi-species biofilms pose a problem in various environments, especially food-processing environments. The diversity of microorganisms in these biofilms plays a critical role in their integrity and protection against external biotic and abiotic factors. Compared to single-species biofilms, mixed-species biofilms are more resistant to various stresses, including antimicrobials like sanitizers. Therefore, understanding the microbiome composition and diversity in biofilms and their metabolic potential is a priority when developing intervention techniques to combat foodborne pathogens in food processing environments.

METHODS: This study aimed to describe and compare the microbiome profile of 75 drain biofilm samples obtained from five different locations (Hotscale, Hotbox, Cooler, Processing, & Grind room) of three beef-processing plants (Plant A, B & C) taken over two timepoints 2017-18 (T1) and 2021 (T2) by shotgun sequencing.

RESULTS: Core microbiome analysis found Pseudomonas, Psychrobacter, and Acinetobacter to be the top three prevalent genera among the plants and locations. Alpha diversity analysis demonstrated a high diversity of microbiome present in all the plants and locations across the time points. Functional analysis showed the high metabolic potential of the microbial community with abundance of genes in metabolism, cell-adhesion, motility, and quorum sensing. Moreover, Quaternary Ammonium Compound (QAC) resistance genes were also observed, this is significant as QAC sanitizers are commonly used in many food processing facilities. Multi-functional genes such as transposases, polymerases, permeases, flagellar proteins, and Mobile Genetic Elements (MGEs) were found suggesting these are dynamic microbial communities that work together to protect themselves against environmental stresses through multiple defense mechanisms.

CONCLUSION: This study provides a framework for understanding the collective microbial network spanning a beef processing system. The results can be used to develop intervention strategies to best control these highly communicative microbial networks.

RevDate: 2023-09-25

Stabel M, Hagemeister J, Heck Z, et al (2021)

Characterization and Phylogenetic Analysis of a Novel GH43 β-Xylosidase From Neocallimastix californiae.

Frontiers in fungal biology, 2:692804.

Degradation of lignocellulosic materials to release fermentable mono- and disaccharides is a decisive step toward a sustainable bio-based economy, thereby increasing the demand of robust and highly active lignocellulolytic enzymes. Anaerobic fungi of the phylum Neocallimastigomycota are potent biomass degraders harboring a huge variety of such enzymes. Compared to cellulose, hemicellulose degradation has received much less attention; therefore, the focus of this study has been the enzymatic xylan degradation of anaerobic fungi as these organisms produce some of the most effective known hydrolytic enzymes. We report the heterologous expression of a GH43 xylosidase, Xyl43Nc, and a GH11 endoxylanase, X11Nc, from the anaerobic fungus Neocallimastix californiae in Escherichia coli. The enzymes were identified by screening of the putative proteome. Xyl43Nc was highly active against 4-Nitrophenol-xylopyranosides with a Km of 0.72 mM, a kcat of 29.28 s[-1], a temperature optimum of 32°C and a pH optimum of 6. When combined, Xyl43Nc and X11Nc released xylose from beechwood xylan and arabinoxylan from wheat. Phylogenetic analysis revealed that Xyl43Nc shares common ancestry with enzymes from Spirochaetes and groups separately from Ascomycete sequences in our phylogeny, highlighting the importance of horizontal gene transfer in the evolution of the anaerobic fungi.

RevDate: 2023-09-24

Gu X (2023)

Genome Distance and Phylogenetic Inference Accommodating Gene Duplication, Loss and New Gene Input.

Molecular phylogenetics and evolution pii:S1055-7903(23)00216-6 [Epub ahead of print].

With the rapid growth of entire genome data, phylogenomics focuses on analyzing evolutionary histories and relationships of species, i.e., the tree of life. For decades it has been realized that the genome-wide phylogenetic inference can be approached based upon the dynamic pattern of gene content (the presence/absence of gene families), or extended gene content (absence, presence as a single-copy, or duplicates). Those methods, conceptually or technically, invoked the birth-and-death process to model the evolutionary process (gene duplication or gene loss. One common drawback is that the mechanism of new gene input, including de novo origin of new genes and the lateral gene transfer, has not been explicitly considered. In this paper, the author developed a new genome distance approach for genome phylogeny inference under the origin-birth-death stochastic process. The model takes gene duplication, gene loss and new gene input into account simultaneously. Computer simulations found that the two-genome approach is statistically difficult to distinguish between two proliferation parameters, i.e., the rate of gene duplication and the rate of new gene input. Nevertheless, it has also demonstrated the statistical feasibility for using the loss-genome distance to infer the genome phylogeny, which can avoid the large sampling problem. The strategy to study the universal tree of life was discussed and exemplified by an example.

RevDate: 2023-09-23

Shen Y, Liu Y, Du Y, et al (2023)

Transfer of antibiotic resistance genes from soil to wheat: Role of host bacteria, impact on seed-derived bacteria, and affecting factors.

The Science of the total environment pii:S0048-9697(23)05906-5 [Epub ahead of print].

The transfer of antibiotic resistance genes (ARGs) from soils to plants is poorly understood, especially the role of host bacteria in soils and its impact on seed-derived bacteria. Wheat (Triticum aestivum L.) was thus used to fill the gap by conducting pot experiments, with target ARGs and bacterial community analyzed. Results showed that the relative abundances of target ARGs gradually decreased during transfer of ARGs from the rhizosphere soil to root and shoot. Host bacteria in the rhizosphere soil were the primary source of ARGs in wheat. The 38, 21, and 19 potential host bacterial genera of target ARGs and intI1 in the rhizosphere soil, root, and shoot were identified, respectively, and they mainly belonged to phylum Proteobacteria. The abundance of ARGs carried by pathogenic Corynebacterium was reduced in sequence. During transfer of ARGs from the rhizosphere soil to root and shoot, some seed-derived bacteria and pathogenic Acinetobacter obtained ARGs through horizontal gene transfer and became potential host bacteria. Furthermore, total organic carbon, available nitrogen of the rhizosphere soil, water use efficiency, vapor pressure deficit, and superoxide dismutase of plants were identified as the key factors affecting potential host bacteria transfer in soils to wheat. This work provides important insights into transfer of ARGs and deepens our understanding of potential health risks of ARGs from soils to plants.

RevDate: 2023-09-22

Khambhati K, Bhattacharjee G, Gohil N, et al (2023)

Exploring the potential of phage and their applications.

Progress in molecular biology and translational science, 200:1-12.

Antibiotic resistant microorganisms are significantly increasing due to horizontal gene transfer, mutation and overdose of antibiotics leading to serious health conditions globally. Several multidrug resistant microorganisms have shown resistance to even the last line of antibiotics making it very difficult to treat them. Besides using antibiotics, an alternative approach to treat such resistant bacterial pathogens through the use of bacteriophage (phage) was used in the early 1900s which however declined and vanished after the discovery of antibiotics. In recent times, phage has emerged and gained interest as an alternative approach to antibiotics to treat MDR pathogens. Phage can self-replicate by utilizing cellular machinery of bacterial host by following lytic and lysogenic life cycles and therefore suitable for rapid regeneration. Application of phage for detection of bacterial pathogens, elimination of bacteria, agents for controlling food spoilage, treating human disease and several others entitles phage as a futuristic antibacterial armamentarium.

RevDate: 2023-09-22

Wu L, Wu Q, Xu J, et al (2023)

Responses of antibiotic resistance genes in the enhanced biological phosphorus removal system under various antibiotics: Mechanisms and implications.

The Science of the total environment pii:S0048-9697(23)05874-6 [Epub ahead of print].

The effects of antibiotics on the proliferation of antibiotic resistant genes (ARGs) in WWTPs have drawn great attention in recent years. The effects of antibiotics on ARGs in the enhanced biological phosphorus removal (EBPR) system and its mechanisms, however, are still not well understood. In this study, EBPR systems were constructed using activated sludge to investigate the effects of ten commonly detected antibiotics in the environment on the proliferation of ARGs and the mechanisms involved. The results showed that the total abundance of ARGs increased to varying degrees with the addition of different antibiotics (0.05 mmol/L), and the top 30 ARGs increased by 271.1 % to 370.0 %. Mobile genetic elements (MGEs), functional modules, and the bacteria community were consistently related to the changes in ARGs. Refractory antibiotics, in particular, have a stronger promoting effect on transduction in the EBPR system. The insertion sequence common region (ISCR) and transposon (Tnp) were identified as crucial factors in the proliferation of ARGs. Moreover, the risk of polyphosphate accumulating organisms (PAOs) carrying ARGs in the presence of antibiotics should not be ignored. Our findings emphasize the potential efficacy of employing strategies that target the reduction of MGEs, regulation of cellular communication, and management of microbial communities to effectively mitigate the risks associated with ARGs.

RevDate: 2023-09-22

Zhang J, Xu Z, Chu W, et al (2023)

Residual chlorine persistently changes antibiotic resistance gene composition and increases the risk of antibiotic resistance in sewer systems.

Water research, 245:120635 pii:S0043-1354(23)01075-8 [Epub ahead of print].

During the COVID-19 pandemic, excessive amounts of disinfectants and their transformation products entered sewer systems worldwide, which was an extremely rare occurrence before. The stress of residual chlorine and disinfection by-products is not only likely to promote the spread of antibiotic resistance genes (ARGs), but also leads to the enrichment of chlorine-resistant bacteria that may also be resistant to antibiotics. Therefore, the potential impact of such discharge on ARG composition should be studied and the health risks should be assessed. Thus, this study combined high-throughput 16S rRNA gene amplicon sequencing and metagenomic analysis with long-term batch tests that involved two stages of stress and recovery to comprehensively evaluate the impact of residual chlorine on the microbial community and ARG compositions in sewer systems. The tests demonstrated that the disturbance of the microbial community structure by residual chlorine was reversible, but the change in ARG composition was persistent. This study found that vertical propagation and horizontal gene transfer jointly drove ARG composition succession in the biofilm, while the driving force was mainly horizontal gene transfer in the sediment. In this process, the biocide resistance gene (BRG) subtype chtR played an important role in promoting co-selection with ARGs through plasmids and integrative and conjugative elements. Moreover, it was further shown that the addition of sodium hypochlorite increased the risk of ARGs to human health, even after discontinuation of dosing, signifying that the impact was persistent. In general, this study strengthens the co-selection theory of ARGs and BRGs, and calls for improved disinfection strategies and more environmentally friendly disinfectants.

RevDate: 2023-09-21

Wang YZ, An XL, Fan XT, et al (2023)

Visible light-activated photosensitizer inhibits the plasmid-mediated horizontal gene transfer of antibiotic resistance genes.

Journal of hazardous materials, 461:132564 pii:S0304-3894(23)01847-2 [Epub ahead of print].

Inhibition of plasmid transfer, including transformation and conjugation, is essential to prevent the spread of plasmid-encoded antimicrobial resistance. Photosensitizers have been successfully used in the treatment of serious infectious diseases, however, the effects of photosensitizers on the plasmid transfer are still elusive. In this study, we determined the transformation and conjugation efficiency of plasmid pUC19 and pRP4, respectively, when exposed to a photosensitizer (Visible Light-activated Rose Bengal, VLRB). The results showed that the activation of VLRB resulted in up to a 580-fold decrease in the transformation frequency of pUC19 and a 10-fold decrease in the conjugation frequency of pRP4 compared with the non-VLRB control. The inhibition of pUC19 transformation by VLRB exhibited a dose-dependent manner and was attributed to the changes in the plasmid conformation. The inhibition of pRP4 conjugation was associated with the generation of extracellular free radicals, induced oxidative stress, suppression of the mating pair formation gene (trbBp) and DNA transfer and replication gene (trfAp), and enhanced expression of the global regulatory genes (korA, korB, and trbA). These findings highlight the potential of visible light-activated photosensitizer for mitigating the dissemination of plasmid-encoded antibiotic resistance genes.

RevDate: 2023-09-21

Caygill S, L Dolan (2023)

ATP binding cassette transporters and uridine diphosphate glycosyltransferases are ancient protein families that evolved roles in herbicide resistance through exaptation.

PloS one, 18(9):e0287356 pii:PONE-D-23-17239.

ATP-binding cassette (ABC) transporters actively transport various substances across membranes, while uridine diphosphate (UDP) glycosyltransferases (UGTs) are proteins that catalyse the chemical modification of various organic compounds. Both of these protein superfamilies have been associated with conferring herbicide resistance in weeds. Little is known about the evolutionary history of these protein families in the Archaeplastida. To infer the evolutionary histories of these protein superfamilies, we compared protein sequences collected from 10 species which represent distinct lineages of the Archaeplastida-the lineage including glaucophyte algae, rhodophyte algae, chlorophyte algae and the streptophytes-and generated phylogenetic trees. We show that ABC transporters were present in the last common ancestor of the Archaeplastida which lived 1.6 billion years ago, and the major clades identified in extant plants were already present then. Conversely, we only identified UGTs in members of the streptophyte lineage, which suggests a loss of these proteins in earlier diverging Archaeplastida lineages or arrival of UGTs into a common ancestor of the streptophyte lineage through horizontal gene transfer from a non-Archaeplastida eukaryote lineage. We found that within the streptophyte lineage, most diversification of the UGT protein family occurred in the vascular lineage, with 17 of the 20 clades identified in extant plants present only in vascular plants. Based on our findings, we conclude that ABC transporters and UGTs are ancient protein families which diversified during Archaeplastida evolution, which may have evolved for developmental functions as plants began to occupy new environmental niches and are now being selected to confer resistance to a diverse range of herbicides in weeds.

RevDate: 2023-09-21

Luo T, Dai X, Wei W, et al (2023)

Microplastics Enhance the Prevalence of Antibiotic Resistance Genes in Anaerobic Sludge Digestion by Enriching Antibiotic-Resistant Bacteria in Surface Biofilm and Facilitating the Vertical and Horizontal Gene Transfer.

Environmental science & technology [Epub ahead of print].

Antibiotic resistance genes (ARGs) and microplastics (MPs) are recognized as emerging contaminants and threats to global human health. Despite both of them being significantly detected in their "hotspots", i.e., waste activated sludge (WAS), rare studies on how MPs affect ARGs and antibiotic-resistant bacteria (ARB) in anaerobic sludge digestion are available. Herein, the fate of ARGs and ARB after exposure to MPs of three dosages (10, 30, and 80 particles/g-TS), three polymer types (LDPE, PET, and PS), and three branching extents (LDPE, LLDPE, and HDPE) in anaerobic sludge digestion was investigated. Metagenomic results indicated that all variants of MPs resulted in an increase of the relative abundance of ARGs in the digester compared to the control. The abundance of ARGs demonstrated a dosage-dependent relationship within the range from 10 to 80 particles/g-TS, resulting in an increase from 4.5 to 27.9% compared to the control. Branching structure and polymer type influence ARG level in the sludge digester as well. Mechanism studies revealed that LDPE selectively enriched potential ARB and ARGs in the surface biofilm, possibly creating a favorable environment for ARB proliferation and ARG exchange. Furthermore, vertical transfer of ARGs was facilitated by LDPE through increasing bacterial cell proliferation accompanied by the enhancement of relevant functional genes. The elevated abundance of mobile genetic elements (MGEs) and ARGs-carrying plasmids also demonstrated that MGE-mediated horizontal transfer was promoted by LDPE at 80 particles/g-TS. This effect was compounded by increased oxidative stress, cell membrane permeability, and cell cohesion, collectively facilitating horizontal ARG transfer. Consequently, both vertical and horizontal transfer of ARGs could be concurrently promoted by LDPE an in anaerobic sludge digester.

RevDate: 2023-09-21

Wirth NT, Rohr K, Danchin A, et al (2023)

Recursive genome engineering decodes the evolutionary origin of an essential thymidylate kinase activity in Pseudomonas putida KT2440.

mBio [Epub ahead of print].

Thymidylate kinases (TMPKs) play an essential role in DNA biosynthesis across all domains of life by catalyzing dTMP phosphorylation to dTDP. In Pseudomonas putida KT2440, a model Gram-negative soil bacterium, tmk is disrupted by a 65-kb genomic island (GI), posing questions about the origin of the essential TMPK function. To solve this long-standing evolutionary riddle, we addressed three competing hypotheses: (i) assembly of two Tmk segments into a functional protein, (ii) complementation by a deoxynucleotide monophosphate kinase encoded within the GI, or (iii) fulfillment of the essential function by the product of PP_3363, yet another gene annotated as "thymidylate kinase." Systematic genome engineering, quantitative physiology and targeted proteomics, complementation assays, phylogenetic analysis, and structure homology modeling were combined to investigate the role of genes within the GI. Our findings revealed that the GI-encoded dNMPK gene PP_1964 plays a critical role in complementing the disrupted TMPK function-exposing a non-essential character for the native PP_3363 gene and the tmk pseudogene. This dNMPK was found to be structurally related to that of bacteriophage T4, as part of a distinct evolutionary domain connected to mobile genetic elements and phages. The recursive genome reduction approach in this work deepens our understanding of the genetic architecture of a model bacterium while it provides evidence that the essential TMPK function has been acquired by horizontal gene transfer. Furthermore, the insights gained in the present study have broader implications for understanding the essentiality and functionality of dNMPK homologs in other bacteria. IMPORTANCE Investigating fundamental aspects of metabolism is vital for advancing our understanding of the diverse biochemical capabilities and biotechnological applications of bacteria. The origin of the essential thymidylate kinase function in the model bacterium Pseudomonas putida KT2440, seemingly interrupted due to the presence of a large genomic island that disrupts the cognate gene, eluded a satisfactory explanation thus far. This is a first-case example of an essential metabolic function, likely acquired by horizontal gene transfer, which "landed" in a locus encoding the same activity. As such, foreign DNA encoding an essential dNMPK could immediately adjust to the recipient host-instead of long-term accommodation and adaptation. Understanding how these functions evolve is a major biological question, and the work presented here is a decisive step toward this direction. Furthermore, identifying essential and accessory genes facilitates removing those deemed irrelevant in industrial settings-yielding genome-reduced cell factories with enhanced properties and genetic stability.

RevDate: 2023-09-20

Shen M, Zhao Y, Liu S, et al (2023)

Can microplastics and disinfectant resistance genes pose conceivable threats to water disinfection process?.

The Science of the total environment pii:S0048-9697(23)05819-9 [Epub ahead of print].

Microplastic pollution in the environment has aroused widespread concerns, however, the potential environmental risks caused by excessive use of disinfectants are still unknown. Disinfectants with doses below the threshold can enhance the communication of resistance genes in pathogenic microorganisms, promoting the development and spread of antimicrobial activity. Problematically, the intensification of microplastic pollution and the increase of disinfectant consumption will become a key driving force for the growth of disinfectant resistance bacteria (DRB) and disinfectant resistance genes (DRGs) in the environment. Disinfection plays a crucial role in ensuring water safety, however, the presence of microplastics and DRGs seriously disturb the water disinfection process. Microplastics can reduce the concentration of disinfectant in the local environment around microorganisms and improve their tolerance. Microorganisms can improve their resistance to disinfectants or generate resistance genes via phenotypic adaptation, gene mutations, and horizontal gene transfer. However, very limited information is available on the impact of DRB and DRGs on disinfection process. In this paper, the contribution of microplastics to the migration and transmission of DRGs was analyzed. The challenges posed by the presence of microplastics and DRGs on conventional disinfection were thoroughly discussed. The knowledge gaps faced by relevant current research and further research priorities have been proposed in order to provide a scientific basis in the future.

RevDate: 2023-09-20

Subirats J, Sharpe H, Tai V, et al (2023)

Metagenome meta-analysis reveals an increase in the abundance of some multidrug efflux pumps and mobile genetic elements in chemically polluted environments.

Applied and environmental microbiology [Epub ahead of print].

Many human activities contaminate terrestrial and aquatic environments with numerous chemical pollutants that not only directly alter the environment but also affect microbial communities in ways that are potentially concerning to human health, such as selecting for the spread of antibiotic-resistance genes (ARGs) through horizontal gene transfer. In the present study, metagenomes available in the public domain from polluted (with antibiotics, with petroleum, with metal mining, or with coal-mining effluents) and unpolluted terrestrial and aquatic environments were compared to examine whether pollution has influenced the abundance and composition of ARGs and mobile elements, with specific focus on IS26 and class 1 integrons (intI1). When aggregated together, polluted environments had a greater relative abundance of ARGs than unpolluted environments and a greater relative abundance of IS26 and intI1. In general, chemical pollution, notably with petroleum, was associated with an increase in the prevalence of ARGs linked to multidrug efflux pumps. Included in the suite of efflux pumps were mexK, mexB, mexF, and mexW that are polyspecific and whose substrate ranges include multiple classes of critically important antibiotics. Also, in some instances, β-lactam resistance (TEM181 and OXA-541) genes increased, and genes associated with rifampicin resistance (RNA polymerases subunits rpoB and rpoB2) decreased in relative abundance. This meta-analysis suggests that different types of chemical pollution can enrich populations that carry efflux pump systems associated with resistance to multiple classes of medically critical antibiotics. IMPORTANCE The United Nations has identified chemical pollution as being one of the three greatest threats to environmental health, through which the evolution of antimicrobial resistance, a seminally important public health challenge, may be favored. While this is a very plausible outcome of continued chemical pollution, there is little evidence or research evaluating this risk. The objective of the present study was to examine existing metagenomes from chemically polluted environments and evaluate whether there is evidence that pollution increases the relative abundance of genes and mobile genetic elements that are associated with antibiotic resistance. The key finding is that for some types of pollution, particularly in environments exposed to petroleum, efflux pumps are enriched, and these efflux pumps can confer resistance to multiple classes of medically important antibiotics that are typically associated with Pseudomonas spp. or other Gram-negative bacteria. This finding makes clear the need for more investigation on the impact of chemical pollution on the environmental reservoir of ARGs and their association with mobile genetic elements that can contribute to horizontal gene transfer events.

RevDate: 2023-09-19

Sabatino R, Sbaffi T, Sivalingam P, et al (2023)

Bacteriophages limitedly contribute to the antimicrobial resistome of microbial communities in wastewater treatment plants.

Microbiology spectrum [Epub ahead of print].

Bacteriophages are known as players in the transmission of antimicrobial resistance genes (ARGs) by horizontal gene transfer. In this study, we characterized the bacteriophage community and the associated ARGs to estimate the potential for phages to spread ARGs in aquatic ecosystems analyzing the intra- and extracellular DNA isolated from two wastewater treatment plants (WWTPs) by shotgun metagenomics. We compared the phage antimicrobial resistome with the bacterial resistome and investigated the effect of the final disinfection treatment on the phage community and its resistome. Phage community was mainly composed by Siphoviridae and other members of the order Caudovirales. The final disinfection only marginally affected the composition of the phage community, and it was not possible to measure its effect on the antimicrobial resistome. Indeed, only three phage metagenome-assembled genomes (pMAGs) annotated as Siphoviridae, Padoviridae, and Myoviridae were positive for putative ARGs. Among the detected ARGs, i.e., dfrB6, rpoB mutants, and EF-Tu mutants, the first one was not annotated in the bacterial MAGs. Overall, these results demonstrate that bacteriophages limitedly contribute to the whole antimicrobial resistome. However, in order to obtain a comprehensive understanding of the antimicrobial resistome within a microbial community, the role of bacteriophages needs to be investigated. IMPORTANCE WWTPs are considered hotspots for the spread of ARGs by horizontal gene transfer. In this study, we evaluated the phage composition and the associated antimicrobial resistome by shotgun metagenomics of samples collected before and after the final disinfection treatment. Only a few bacteriophages carried ARGs. However, since one of the detected genes was not found in the bacterial metagenome-assembled genomes, it is necessary to investigate the phage community in order to gain a comprehensive overview of the antimicrobial resistome. This investigation could help assess the potential threats to human health.

RevDate: 2023-09-19

Derbyshire KM, M Salfinger (2023)

Plasmid-mediated drug resistance in mycobacteria: the tip of the iceberg?.

Journal of clinical microbiology [Epub ahead of print].

Macrolides, such as clarithromycin, are crucial in the treatment of nontuberculous mycobacteria (NTM). NTM are notoriously innately drug resistant, which has made the dependence on macrolides for their treatment even more important. Not surprisingly, resistance to macrolides has been documented in some NTM, including Mycobacterium avium and Mycobacterium abscessus, which are the two NTM species most often identified in clinical isolates. Resistance is mediated by point mutations in the 23S ribosomal RNA or by methylation of the rRNA by a methylase (encoded by an erm gene). Chromosomally encoded erm genes have been identified in many of the macrolide-resistant isolates, but not in Mycobacterium chelonae. Now, Brown-Elliott et al. (J Clin Microbiol 61:e00428-23, 2023, describe the identification of a new erm variant, erm(55), which was found either on the chromosome or on a plasmid in highly macrolide-resistant clinical isolates of M. chelonae. The chromosomal erm(55) gene appears to be associated with mobile elements; one gene is within a putative transposon and the second is in a large (37 kb) insertion/deletion. The plasmid carrying erm(55) also encodes type IV and type VII secretion systems, which are often linked on large mycobacterial plasmids and are hypothesized to mediate plasmid transfer. While the conjugative transfer of the erm(55)-containing plasmid between NTM has yet to be demonstrated, the inferences are clear, as evidenced by the dissemination of plasmid-mediated drug resistance in other medically important bacteria. Here, we discuss the findings of Brown-Elliott et al., and the potential ramifications on treatment of NTM infections.

RevDate: 2023-09-18

Bhat BA, Mir RA, Qadri H, et al (2023)

Integrons in the development of antimicrobial resistance: critical review and perspectives.

Frontiers in microbiology, 14:1231938.

Antibiotic resistance development and pathogen cross-dissemination are both considered essential risks to human health on a worldwide scale. Antimicrobial resistance genes (AMRs) are acquired, expressed, disseminated, and traded mainly through integrons, the key players capable of transferring genes from bacterial chromosomes to plasmids and their integration by integrase to the target pathogenic host. Moreover, integrons play a central role in disseminating and assembling genes connected with antibiotic resistance in pathogenic and commensal bacterial species. They exhibit a large and concealed diversity in the natural environment, raising concerns about their potential for comprehensive application in bacterial adaptation. They should be viewed as a dangerous pool of resistance determinants from the "One Health approach." Among the three documented classes of integrons reported viz., class-1, 2, and 3, class 1 has been found frequently associated with AMRs in humans and is a critical genetic element to serve as a target for therapeutics to AMRs through gene silencing or combinatorial therapies. The direct method of screening gene cassettes linked to pathogenesis and resistance harbored by integrons is a novel way to assess human health. In the last decade, they have witnessed surveying the integron-associated gene cassettes associated with increased drug tolerance and rising pathogenicity of human pathogenic microbes. Consequently, we aimed to unravel the structure and functions of integrons and their integration mechanism by understanding horizontal gene transfer from one trophic group to another. Many updates for the gene cassettes harbored by integrons related to resistance and pathogenicity are extensively explored. Additionally, an updated account of the assessment of AMRs and prevailing antibiotic resistance by integrons in humans is grossly detailed-lastly, the estimation of AMR dissemination by employing integrons as potential biomarkers are also highlighted. The current review on integrons will pave the way to clinical understanding for devising a roadmap solution to AMR and pathogenicity. Graphical AbstractThe graphical abstract displays how integron-aided AMRs to humans: Transposons capture integron gene cassettes to yield high mobility integrons that target res sites of plasmids. These plasmids, in turn, promote the mobility of acquired integrons into diverse bacterial species. The acquisitions of resistant genes are transferred to humans through horizontal gene transfer.

RevDate: 2023-09-17

You L, Jin H, Kwok LY, et al (2023)

Intraspecific microdiversity and ecological drivers of lactic acid bacteria in naturally fermented milk ecosystem.

Science bulletin pii:S2095-9273(23)00617-5 [Epub ahead of print].

Traditional fermented milks are produced by inoculating technique, which selects well-adapted microorganisms that have been passed on through generations. Few reports have used naturally fermented milks as model ecosystems to investigate the mechanism of formation of intra-species microbial diversity. Here, we isolated and whole-genome-sequenced a total of 717 lactic acid bacterial isolates obtained from 12 independent naturally fermented milks collect from 12 regions across five countries. We further analyzed the within-sample intra-species phylogenies of 214 Lactobacillus helveticus isolates, 97 Lactococcus lactis subsp. lactis isolates, and 325 Lactobacillus delbrueckii subsp. bulgaricus isolates. We observed a high degree of intra-species genomic and functional gene diversity within-/between-sample(s). Single nucleotide polymorphism-based phylogenetic reconstruction revealed great within-sample intra-species heterogeneity, evolving from multiple lineages. Further phylogenetic reconstruction (presence-absence gene profile) revealed within-sample inter-clade functional diversity (based on carbohydrate-active enzyme- and peptidase-encoding genes) in all three investigated species/subspecies. By identifying and mapping clade-specific genes of intra-sample clades of the three species/subspecies to the respective fermented milk metagenome, we found extensive potential inter-/intra-species horizontal gene transfer events. Finally, the microbial composition of the samples is closely linked to the nucleotide diversity of the respective species/subspecies. Overall, our results contribute to the conservation of lactic acid bacteria resources, providing ecological insights into the microbial ecosystem of naturally fermented dairy products.

RevDate: 2023-09-16

Rodríguez-Pallares S, Mateo-Vargas MA, Rodríguez-Iglesias MA, et al (2023)

Molecular Characterization of consecutive isolates of OXA-48-producing Klebsiella pneumoniae: Changes in the virulome using next-generation sequencing (NGS).

Microbes and infection pii:S1286-4579(23)00120-X [Epub ahead of print].

Little is known about the clonality of consecutive OXA-48 producing-Klebsiella pneumoniae isolates from the same patient and the possibility of changes in their virulomes over time. We studied the molecular characteristics of twenty OXA-48-producing K. pneumoniae consecutive isolates from six patients using whole-genome sequencing. The genomes were screened for antimicrobial resistance and virulence factor genes and for replicon groups. MLST and SNPs analysis was performed. MLST analysis found 3 STs: ST11 (n=13; 65.0%); ST4975 (n=5, 25.0%); ST307 (n=2; 10.0%). AcrAb efflux pump, siderophore enterobactin and rcsAB capsule synthesis regulator were detected in all sequenced isolates. The regulator of mucoid phenotype A (rmpA) and rmpA2 were not detected. Isolates also carried type 3 fimbriae (n=19; 95.0%), yersiniabactin (n=15; 75.0%) and type 1 fimbriae (7; 35.0%). Type 3 fimbriae and yersiniabactin were lost and recovered in consecutive isolates of two patients, probably acquired by horizontal gene transfer. Our findings reveal that recurrent infections are due to the same isolate, with an average of 2.69 SNPs per month, with different virulence profiles, and that the acquisition of virulence factor genes over time is possible.

RevDate: 2023-09-16

Savin M, Hammerl JA, Hassa J, et al (2023)

Free-floating extracellular DNA (exDNA) in different wastewaters: Status quo on exDNA-associated antimicrobial resistance genes.

Environmental pollution (Barking, Essex : 1987) pii:S0269-7491(23)01562-2 [Epub ahead of print].

Wastewater treatment plants (WWTPs) have been reported as major anthropogenic reservoirs for the spread of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) into the environment, worldwide. While most studies mainly focus on the intracellular DNA (iDNA), extracellular DNA (exDNA) accounting for a significant proportion of the total DNA in wastewater, was usually neglected. Following the One Health approach, this study focuses on wastewaters of municipal, clinical, and livestock origins (n = 45) that undergo different treatment processes (i.e., conventional activated sludge, ultrafiltration, and ozonation). Water samples were analysed for 12 ARGs as indicators of the different compartments associated with iDNA and exDNA by quantitative real-time PCR (qPCR). Taxonomic profiling of exDNA-fractions, obtained using nucleic acid adsorption particles, was conducted by sequencing the V3-V4 hypervariable regions of the 16S rRNA gene. Notified exDNA concentrations varied between on-site WWTPs and treatment stages, and ranged from 314.0 ± 70.2 ng/mL in untreated livestock wastewater down to 0.7 ± 0.1 ng/mL in effluents after ultrafiltration. In general, influents exhibited higher concentrations compared to effluents, while wastewater treated by advanced treatment processes (i.e., ultrafiltration and ozonation) showed the lowest exDNA concentrations. Despite the lower concentrations, free-floating exDNA accounted for up to 80.0 ± 5.8% of the total DNA in effluents. Target ARGs were more common in the iDNA (100%, n = 45/45), compared to the exDNA-fractions (51.1%, n = 23/45), whereas exDNA-ARGs were mostly detected in clinical and slaughterhouse wastewaters as well as in the municipal influents. Compared to the iDNA-ARGs, the concentrations of exDNA-ARGs were in general lower. Nevertheless, significant higher concentrations for exDNA-associated genes were measured in clinical wastewaters for blaNDM (4.07 ± 0.15 log gene copies (GC)/L) and blaVIM-2 (6.0 ± 0.2 log GC/L). Overall, our results suggest that depending on the origin of wastewater and its treatment methods, exDNA represents an important reservoir for ARGs, particularly in clinical wastewater.

RevDate: 2023-09-15

Xi Y, Zhao J, Zhang J, et al (2023)

Analysis of the features of 105 confirmed CRISPR loci in 487 Klebsiella variicola.

Letters in applied microbiology pii:7275100 [Epub ahead of print].

Klebsiella variicola (K. variicola), an emerging human pathogen, poses a threat to public health. The horizontal gene transfer (HGT) of plasmids is an important driver of the emergence of multiple antibiotic-resistant K. variicola. Clustered regularly interspersed short palindromic repeats (CRISPR) coupled with CRISPR-associated genes (CRISPR/Cas) constitute an adaptive immune system in bacteria, and can provide acquired immunity against HGT. However, the information about the CRISPR/Cas system in K. variicola is still limited. In this study, 487 genomes of K. variicola obtained from the National Center for Biotechnology Information database were used to analyze the characteristics of CRISPR/Cas systems. Approximately 21.56% of genomes (105/487) harbor at least one confirmed CRISPR array. Three types of CRISPR/Cas systems, namely, the types I-E, I-E*, and IV-A systems, were identified among 105 strains. Spacer origin analysis further revealed that approximately one-third of spacers significantly match plasmids or phages, which demonstrates the implication of CRISPR/Cas systems in controlling HGT. Moreover, spacers in K. variicola tend to target mobile genetic elements from K. pneumoniae. This finding provides new evidence of the interaction of K. variicola and K. pneumoniae during their evolution. Collectively, our results provide valuable insights into the role of CRISPR/Cas systems in K. variicola.

RevDate: 2023-09-15

Milner DS, Galindo LJ, Irwin NAT, et al (2023)

Transporter Proteins as Ecological Assets and Features of Microbial Eukaryotic Pangenomes.

Annual review of microbiology, 77:45-66.

Here we review two connected themes in evolutionary microbiology: (a) the nature of gene repertoire variation within species groups (pangenomes) and (b) the concept of metabolite transporters as accessory proteins capable of providing niche-defining "bolt-on" phenotypes. We discuss the need for improved sampling and understanding of pangenome variation in eukaryotic microbes. We then review the factors that shape the repertoire of accessory genes within pangenomes. As part of this discussion, we outline how gene duplication is a key factor in both eukaryotic pangenome variation and transporter gene family evolution. We go on to outline how, through functional characterization of transporter-encoding genes, in combination with analyses of how transporter genes are gained and lost from accessory genomes, we can reveal much about the niche range, the ecology, and the evolution of virulence of microbes. We advocate for the coordinated systematic study of eukaryotic pangenomes through genome sequencing and the functional analysis of genes found within the accessory gene repertoire.

RevDate: 2023-09-14

Abdelbary ER, Elsaghier AM, Abd El-Baky RM, et al (2023)

First Emergence of NDM-5 and OqxAB Efflux Pumps Among Multidrug-Resistant Klebsiella pneumoniae Isolated from Pediatric Patients in Assiut, Egypt.

Infection and drug resistance, 16:5965-5976 pii:421978.

INTRODUCTION: New Delhi metallo-β-lactamase (NDM)-producing K. pneumoniae poses a high risk, especially among Egyptian pediatric patients who consume carbapenems antibiotics very widely and without adequate diagnostic sources. In addition, presence of efflux pump genes such as OqxAB increases resistance against many groups of antimicrobials which exacerbates the problem faced for human health. This study aimed to determine NDM variants among K. pneumoniae strains isolated from pediatric patients in Egypt, analyze the presence of OqxAB genes, and molecular characterization of blaNDM-5-positive K. pneumoniae.

METHODS: Fifty-six K. pneumoniae isolates were recovered from pediatric patients, and tested for carbapenemase by modified carbapenem inactivation methods (mCIM) test. Minimum inhibitory concentrations of meropenem and colistin were determined by meropenem E-test strips and broth microdilution, respectively. PCR was used for the detection of the resistant genes (ESBL gene (blaCTX-M), carbapenemase genes (blaNDM, blaKPC) colistin resistant (mcr1, mcr2)) and genes for efflux pump (oqxA and oqxB). BlaNDM was sequenced. The effect of efflux pump in NDM-5-producing isolates was assessed by measuring MIC of ciprofloxacin and meropenem before and after exposure to the carbonyl cyanide 3-chlorophenylhydrazone (CCCP). The horizontal gene transfer ability of blaNDM-5 was determined using liquid mating assay and PCR-based replicon typing (PBRT) was done to determine the major plasmid incompatibility group.

RESULTS: Twenty-nine isolates were positive for blaNDM-1, nine isolates were positive for blaNDM-5, and 15 isolates were positive for blaKPC. There is a significant increase of meropenem MIC of NDM-5-positive isolates compared with NDM-1-positive isolates. In addition, 38 isolates were positive for CTX-M, and 15 isolates were positive for mcr1. Both OqxA and OqxB were detected in 26 isolates and 13 isolates were positive for OqxA while 11 isolates were positive for OqxB only. All NDM-5-producing isolates except one isolate could transfer their plasmids by conjugation to their corresponding transconjugants (E. coli J53). Plasmid replicon typing showed that FII was predominant in NDM-5-producing K. pneumoniae. Similar strains were found between the three isolates and similarity was also detected between the two isolates.

CONCLUSION: The highly resistant K. pneumoniae producing blaNDM-5 type was firstly isolated from pediatric patients. The association of efflux pump genes such as OqxAB is involved in resistance to ciprofloxacin. This highlighted the severity risk of blaNDM-5-positive K. pneumonia as it could transfer blaNDM-5 to other bacteria and has more resistance against carbapenems. This underlines the importance of continuous monitoring of infection control guidelines, and the urgent need for a national antimicrobial stewardship plan in Egyptian hospitals.

RevDate: 2023-09-13

Nasir A, Caetano-Anollés G, JM Claverie (2023)

Editorial: Viruses, genetic exchange, and the tree of life, volume II.

Frontiers in microbiology, 14:1271181.

RevDate: 2023-09-12

Lin X, Zhang C, Han R, et al (2023)

Oxytetracycline and heavy metals promote the migration of resistance genes in the intestinal microbiome by plasmid transfer.

The ISME journal [Epub ahead of print].

Horizontal gene transfer (HGT) has been considered the most important pathway to introduce antibiotic resistance genes (ARGs), which seriously threatens human health and biological security. The presence of ARGs in the aquatic environment and their effect on the intestinal micro-ecosystem of aquatic animals can occur easily. To investigate the HGT potential and rule of exogenous ARGs in the intestinal flora, a visual conjugative model was developed, including the donor of dual-fluorescent bacterium and the recipient of Xenopus tropicalis intestinal microbiome. Some common pollutants of oxytetracycline (OTC) and three heavy metals (Zn, Cu and Pb) were selected as the stressor. The multi-techniques of flow cytometry (FCM), scanning electron microscopy (SEM), atomic force microscopy (AFM), single-cell Raman spectroscopy with sorting (SCRSS) and indicator analysis were used in this study. The results showed that ARG transfer could occur more easily under stressors. Moreover, the conjugation efficiency mainly depended on the viability of the intestinal bacteria. The mechanisms of OTC and heavy metal stressing conjugation included the upregulation of ompC, traJ, traG and the downregulation of korA gene. Moreover, the enzymatic activities of SOD, CAT, GSH-PX increased and the bacterial surface appearance also changed. The predominant recipient was identified as Citrobacter freundi by SCRSS, in which the abundance and quantity of ARG after conjugation were higher than those before. Therefore, since the diversity of potential recipients in the intestine are very high, the migration of invasive ARGs in the microbiome should be given more attention to prevent its potential risks to public health.

RevDate: 2023-09-11

El-Sabeh A, Mlesnita AM, Munteanu IT, et al (2023)

Characterisation of the Paenarthrobacter nicotinovorans ATCC 49919 genome and identification of several strains harbouring a highly syntenic nic-genes cluster.

BMC genomics, 24(1):536.

BACKGROUND: Paenarthrobacter nicotinovorans ATCC 49919 uses the pyridine-pathway to degrade nicotine and could provide a renewable source of precursors from nicotine-containing waste as well as a model for studying the molecular evolution of catabolic pathways and their spread by horizontal gene transfer via soil bacterial plasmids.

RESULTS: In the present study, the strain was sequenced using the Illumina NovaSeq 6000 and Oxford Nanopore Technology (ONT) MinION platforms. Following hybrid assembly with Unicycler, the complete genome sequence of the strain was obtained and used as reference for whole-genome-based phylogeny analyses. A total of 64 related genomes were analysed; five Arthrobacter strains showed both digital DNA-DNA hybridization and average nucleotide identity values over the species threshold when compared to P. nicotinovorans ATCC 49919. Five plasmids and two contigs belonging to Arthrobacter and Paenarthrobacter strains were shown to be virtually identical with the pAO1 plasmid of Paenarthrobacter nicotinovorans ATCC 49919. Moreover, a highly syntenic nic-genes cluster was identified on five plasmids, one contig and three chromosomes. The nic-genes cluster contains two major locally collinear blocks that appear to form a putative catabolic transposon. Although the origins of the nic-genes cluster and the putative transposon still elude us, we hypothesise here that the ATCC 49919 strain most probably evolved from Paenarthrobacter sp. YJN-D or a very closely related strain by acquiring the pAO1 megaplasmid and the nicotine degradation pathway.

CONCLUSIONS: The data presented here offers another snapshot into the evolution of plasmids harboured by Arthrobacter and Paenarthrobacter species and their role in the spread of metabolic traits by horizontal gene transfer among related soil bacteria.

RevDate: 2023-09-11

Doughty EL, Liu H, Moran RA, et al (2023)

Endemicity and diversification of carbapenem-resistant Acinetobacter baumannii in an intensive care unit.

The Lancet regional health. Western Pacific, 37:100780 pii:S2666-6065(23)00098-6.

BACKGROUND: Carbapenem-resistant Acinetobacter baumannii (CRAB) is a major public health concern globally. Often studied in the context of hospital outbreaks, little is known about the persistence and evolutionary dynamics of endemic CRAB populations.

METHODS: A three-month cross-sectional observational study was conducted in a 28-bed intensive care unit (ICU) in Hangzhou, China. A total of 5068 samples were collected from the hospital environment (n = 3985), patients (n = 964) and staff (n = 119). CRAB isolates were obtained from 10.5% of these samples (n = 532). All of these isolates, plus an additional 19 from clinical infections, were characterised through whole-genome sequencing.

FINDINGS: The ICU CRAB population was dominated by OXA-23-producing global clone 2 isolates (99.3% of all isolates) that could be divided into 20 distinct clusters, defined through genome sequencing. CRAB was persistently present in the ICU, driven by regular introductions of distinct clusters. The hospital environment was heavily contaminated, with CRAB isolated from bed units on 183/335 (54.6%) sampling occasions but from patients on only 72/299 (24.1%) occasions. CRAB was spread to adjacent bed units and rooms, and following re-location of patients within the ICU. We also observed three horizontal gene transfer events between CRAB strains in the ICU, involving three different plasmids.

INTERPRETATION: The epidemiology of CRAB in this setting contrasted with previously described clonal outbreaks in high-income countries, highlighting the importance of environmental CRAB reservoirs in ICU epidemiology and the unique challenges in containing the spread of CRAB in ICUs where this important multidrug-resistant pathogen is endemic.

FUNDING: This work was undertaken as part of the DETECTIVE research project funded by the Medical Research Council (MR/S013660/1), National Natural Science Foundation of China (81861138054, 32011530116, 31970128, 31770142), Zhejiang Province Medical Platform Backbone Talent Plan (2020RC075), and the National Key Research and Development Program of China grant (2018YFE0102100). W.v.S was also supported by a Wolfson Research Merit Award (WM160092).

RevDate: 2023-09-11

Fox BW, Helf MJ, Burkhardt RN, et al (2023)

Evolutionarily related host and microbial pathways regulate fat desaturation.

bioRxiv : the preprint server for biology pii:2023.08.31.555782.

Fatty acid desaturation is central to metazoan lipid metabolism and provides building blocks of membrane lipids and precursors of diverse signaling molecules. Nutritional conditions and associated microbiota regulate desaturase expression [1-4] , but the underlying mechanisms have remained unclear. Here, we show that endogenous and microbiota-dependent small molecule signals promote lipid desaturation via the nuclear receptor NHR-49/PPARα in C. elegans . Untargeted metabolomics of a β-oxidation mutant, acdh-11 , in which expression of the stearoyl-CoA desaturase FAT-7/SCD1 is constitutively increased, revealed accumulation of a β- cyclopropyl fatty acid, becyp#1, that potently activates fat-7 expression via NHR-49. Biosynthesis of becyp#1 is strictly dependent on expression of cyclopropane synthase by associated bacteria, e.g., E. coli . Screening for structurally related endogenous metabolites revealed a β-methyl fatty acid, bemeth#1, whose activity mimics that of microbiota-dependent becyp#1, but is derived from a methyltransferase, fcmt-1 , that is conserved across Nematoda and likely originates from bacterial cyclopropane synthase via ancient horizontal gene transfer. Activation of fat-7 expression by these structurally similar metabolites is controlled by distinct mechanisms, as microbiota-dependent becyp#1 is metabolized by a dedicated β-oxidation pathway, while the endogenous bemeth#1 is metabolized via α-oxidation. Collectively, we demonstrate that evolutionarily related biosynthetic pathways in metazoan host and associated microbiota converge on NHR-49/PPARα to regulate fat desaturation.

RevDate: 2023-09-11

Li Z, Xue AZ, Maeda GP, et al (2023)

Phylloxera and aphids show distinct features of genome evolution despite similar reproductive modes.

bioRxiv : the preprint server for biology pii:2023.08.28.555181.

Genomes of aphids (family Aphididae) show several unusual evolutionary patterns. In particular, within the XO sex determination system of aphids, the X chromosome exhibits a lower rate of interchromosomal rearrangements, fewer highly expressed genes, and faster evolution at nonsynonymous sites compared to the autosomes. In contrast, other hemipteran lineages have similar rates of interchromosomal rearrangement for autosomes and X chromosomes. One possible explanation for these differences is the aphid's life cycle of cyclical parthenogenesis, where multiple asexual generations alternate with one sexual generation. If true, we should see similar features in the genomes of Phylloxeridae, an outgroup of aphids which also undergoes cyclical parthenogenesis. To investigate this, we generated a chromosome-level assembly for the grape phylloxera, an agriculturally important species of Phylloxeridae, and identified its single X chromosome. We then performed synteny analysis using the phylloxerid genome and 30 high-quality genomes of aphids and other hemipteran species. Unexpectedly, we found that the phylloxera does not share aphids' patterns of chromosome evolution. By estimating interchromosomal rearrangement rates on an absolute time scale, we found that rates are elevated for aphid autosomes compared to their X chromosomes, but this pattern does not extend to the phylloxera branch. Potentially, the conservation of X chromosome gene content is due to selection on XO males that appear in the sexual generation. We also examined gene duplication patterns across Hemiptera and uncovered horizontal gene transfer events contributing to phylloxera evolution.

RevDate: 2023-09-11

Chang H, Bai J, Zhang H, et al (2023)

Origin and evolution of the main starch biosynthetic enzymes.

Synthetic and systems biotechnology, 8(3):462-468 pii:S2405-805X(23)00036-4.

Starch, a semi-crystalline energy storage form primarily found in plant plastids plays a crucial role in various food or no-food applications. Despite the starch biosynthetic pathway's main enzymes have been characterized, their origin and evolution remained a subject of debate. In this study, we conducted the comprehensive phylogenetic and structural analysis of three types of starch biosynthetic enzymes: starch synthase (SS), starch branching enzyme (SBE) and isoamylase-type debranching enzyme (ISA) from 51,151 annotated genomes. Our findings provide valuable insights into the possible scenario for the origin and evolution of the starch biosynthetic pathway. Initially, the ancestor of SBE can be traced back to an unidentified bacterium that existed before the formation of the last eukaryotic common ancestor (LECA) via horizontal gene transfer (HGT). This transfer event likely provided the eukaryote ancestor with the ability to synthesize glycogen. Furthermore, during the emergence of Archaeplastida, one clade of SS was transferred from Deltaproteobacteria by HGT, while ISA and the other clade of SS originated from Chlamydiae through endosymbiosis gene transfer (EGT). Both these transfer events collectively contributed to the establishment of the original starch biosynthetic pathway. Subsequently, after the divergence of Viridiplantae from Rhodophyta, all three enzymes underwent multiple duplications and N-terminus extension domain modifications, resulting in the formation of functionally specialized isoforms and ultimately leading to the complete starch biosynthetic pathway. By shedding light on the evolutionary origins of key enzymes involved in the starch biosynthetic pathway, this study provides important insights into the evolutionary events of plants.

RevDate: 2023-09-10

Haghjooy Javanmard S, Rafiee L, Bahri Najafi M, et al (2023)

Microfluidic-based technologies in cancer liquid biopsy: Unveiling the role of horizontal gene transfer (HGT) materials.

Environmental research pii:S0013-9351(23)01887-X [Epub ahead of print].

Liquid biopsy includes the isolating and analysis of non-solid biological samples enables us to find new ways for molecular profiling, prognostic assessment, and better therapeutic decision-making in cancer patients. Despite the conventional theory of tumor development, a non-vertical transmission of DNA has been reported among cancer cells and between cancer and normal cells. The phenomenon referred to as horizontal gene transfer (HGT) has the ability to amplify the advancement of tumors by disseminating genes that encode molecules conferring benefits to the survival or metastasis of cancer cells. Currently, common liquid biopsy approaches include the analysis of extracellular vesicles (EVs) and tumor-free DNA (tfDNA) derived from primary tumors and their metastatic sites, which are well-known HGT mediators in cancer cells. Current technological and molecular advances expedited the high-throughput and high-sensitive HGT materials analyses by using new technologies, such as microfluidics in liquid biopsies. This review delves into the convergence of microfluidic-based technologies and the investigation of Horizontal Gene Transfer (HGT) materials in cancer liquid biopsy. The integration of microfluidics offers unprecedented advantages such as high sensitivity, rapid analysis, and the ability to analyze rare cell populations. These attributes are instrumental in detecting and characterizing CTCs, circulating nucleic acids, and EVs, which are carriers of genetic cargo that could potentially undergo HGT. The phenomenon of HGT in cancer has raised intriguing questions about its role in driving genomic diversity and acquired drug resistance. By leveraging microfluidic platforms, researchers have been able to capture and analyze individual cells or genetic material with enhanced precision, shedding light on the potential transfer of genetic material between cancer cells and surrounding stromal cells. Furthermore, the application of microfluidics in single-cell sequencing has enabled the elucidation of the genetic changes associated with HGT events, providing insights into the evolution of tumor genomes. This review also discusses the challenges and opportunities in studying HGT materials using microfluidic-based technologies. In conclusion, microfluidic-based technologies have significantly advanced the field of cancer liquid biopsy, enabling the sensitive and accurate detection of HGT materials. As the understanding of HGT's role in tumor evolution and therapy resistance continues to evolve, the synergistic integration of microfluidics and HGT research promises to provide valuable insights into cancer biology, with potential implications for precision oncology and therapeutic strategies.

RevDate: 2023-09-09

Hull DM, Harrel E, Harden L, et al (2023)

Detection of resistance and virulence plasmids in Campylobacter coli and Campylobacter jejuni isolated from North Carolina food animal production, 2018-2019.

Food microbiology, 116:104348.

Campylobacter remains the leading cause of bacterial foodborne illness in the U.S. and worldwide. Campylobacter plasmids may play a significant role in antimicrobial resistance (AMR) and virulence factor distribution, and potentially drive rapid adaptation. C. coli (n = 345) and C. jejuni (n = 199) isolates collected from live cattle, swine, turkey, and chickens, poultry carcasses at production, and retail meat in N.C. were analyzed to determine plasmid prevalence, extrachromosomal virulence and AMR genes, and the phylogeny of assembled plasmids. Putative plasmids ranging from <2 kb to 237kb were identified with virulence factors present in 66.1% (228/345) C. coli and 88.4% (176/199) C. jejuni plasmids (promoting adherence, invasion, exotoxin production, immune modulation, chemotaxis, mobility, and the type IV secretion system). AMR genes were identified in 21.2% (73/345) C. coli and 28.1% C. jejuni plasmids (conferring resistance to tetracyclines, aminoglycosides, beta-lactams, nucleosides, and lincosamides). Megaplasmids (>100 kb) were present in 25.7% (140/544) of the isolates and carried genes previously recognized to be involved with interspecies recombination. Our study highlights the extensive distribution and diversity of Campylobacter plasmids in food animal production and their role in the dissemination of biomedically important genes. Characterizing Campylobacter plasmids within the food animal production niche is important to understanding the epidemiology of potential emerging strains.

RevDate: 2023-09-08

Ashy RA (2023)

Functional analysis of bacterial genes accidentally packaged in rhizospheric phageome of the wild plant species Abutilon fruticosum.

Saudi journal of biological sciences, 30(10):103789.

The study aimed to reveal the structure and function of phageome existing in soil rhizobiome of Abutilon fruticosum in order to detect accidentally-packaged bacterial genes that encode Carbohydrate-Active enZymes (or CAZymes) and those that confer antibiotic resistance (e.g., antibiotic resistance genes or ARGs). Highly abundant genes were shown to mainly exist in members of the genera Pseudomonas, Streptomyces, Mycobacterium and Rhodococcus. Enriched CAZymes belong to glycoside hydrolase families GH4, GH6, GH12, GH15 and GH43 and mainly function in D-glucose biosynthesis via 10 biochemical passages. Another enriched CAZyme, e.g., alpha-galactosidase, of the GH4 family is responsible for the wealth of different carbohydrate forms in rhizospheric soil sink of A. fruticosum. ARGs of this phageome include the soxR and OleC genes that participate in the "antibiotic efflux pump" resistance mechanism, the parY mutant gene that participates in the "antibiotic target alteration" mechanism and the arr-1, iri, and AAC(3)-Ic genes that participate in the "antibiotic inactivation" mechanism. It is claimed that the genera Streptomyces, which harbors phages with oleC and parY mutant genes, and Pseudomonas, which harbors phages with soxR and AAC(3)-Ic genes, are approaching multidrug resistance via newly disseminating phages. These ARGs inhibit many antibiotics including oleandomycin, tetracycline, rifampin and aminoglycoside. The study highlights the possibility of accidental packaging of these ARGs in soil phageome and the risk of their horizontal transfer to human gut pathogens through the food chain as detrimental impacts of soil phageome of A. fruticosum. The study also emphasizes the beneficial impacts of phageome on soil microbiome and plant interacting in storing carbohydrates in the soil sink for use by the two entities upon carbohydrate deprivation.

RevDate: 2023-09-06
CmpDate: 2023-09-06

Hallal Ferreira Raro O, Poirel L, Tocco M, et al (2023)

Impact of veterinary antibiotics on plasmid-encoded antibiotic resistance transfer.

The Journal of antimicrobial chemotherapy, 78(9):2209-2216.

OBJECTIVES: Resistance genes can be genetically transmitted and exchanged between commensal and pathogenic bacterial species, and in different compartments including the environment, or human and animal guts (One Health concept). The aim of our study was to evaluate whether subdosages of antibiotics administered in veterinary medicine could enhance plasmid transfer and, consequently, resistance gene exchange in gut microbiota.

METHODS: Conjugation frequencies were determined with Escherichia coli strains carrying IncL- (blaOXA-48) or IncI1-type (blaCTX-M-1) plasmids subjected to a series of subinhibitory concentrations of antibiotics used in veterinary medicine, namely amoxicillin, ceftiofur, apramycin, neomycin, enrofloxacin, colistin, erythromycin, florfenicol, lincomycin, oxytetracycline, sulfamethazine, tiamulin and the ionophore narasin. Treatments with subinhibitory dosages were performed with and without supplementation with the antioxidant edaravone, known as a mitigator of the inducibility effect of several antibiotics on plasmid conjugation frequency (PCF). Expression of SOS-response associated genes and fluorescence-based reactive oxygen species (ROS) detection assays were performed to evaluate the stress oxidative response.

RESULTS: Increased PCFs were observed for both strains when treating with florfenicol and oxytetracycline. Increased expression of the SOS-associated recA gene also occurred concomitantly, as well as increased ROS production. Addition of edaravone to the treatments reduced their PCF and also showed a decreasing effect on SOS and ROS responses for both plasmid scaffolds.

CONCLUSIONS: We showed here that some antibiotics used in veterinary medicine may induce transfer of plasmid-encoded resistance and therefore may contribute to the worldwide spread of antibiotic resistance genes.

RevDate: 2023-09-05

Natarajan S, Pucker B, S Srivastava (2023)

Genomic and transcriptomic analysis of camptothecin producing novel fungal endophyte: Alternaria burnsii NCIM 1409.

Scientific reports, 13(1):14614.

Camptothecin is an important anticancer alkaloid produced by particular plant species. No suitable synthetic route has been established for camptothecin production yet, imposing a stress on plant-based production systems. Endophytes associated with these camptothecin-producing plants have been reported to also produce camptothecin and other high-value phytochemicals. A previous study identified a fungal endophyte Alternaria burnsii NCIM 1409, isolated from Nothapodytes nimmoniana, to be a sustainable producer of camptothecin. Our study provides key insights on camptothecin biosynthesis in this recently discovered endophyte. The whole genome sequence of A. burnsii NCIM 1409 was assembled and screened for biosynthetic gene clusters. Comparative studies with related fungi supported the identification of candidate genes involved in camptothecin synthesis and also helped to understand some aspects of the endophyte's defense against the toxic effects of camptothecin. No evidence for horizontal gene transfer of the camptothecin biosynthetic genes from the host plant to the endophyte was detected suggesting an independent evolution of the camptothecin biosynthesis in this fungus.

RevDate: 2023-09-04

Takahashi T, Kim H, Kim HS, et al (2024)

Comparative Genomic Analysis of Staphylococcal Cassette Chromosome mec Type V Staphylococcus aureus Strains and Estimation of the Emergence of SCCmec V Clinical Isolates in Korea.

Annals of laboratory medicine, 44(1):47-55.

BACKGROUND: Staphylococcal cassette chromosome mec type V (SCCmec V) methicillin-resistant Staphylococcus aureus (MRSA) has been recovered from patients and livestock. Using comparative genomic analyses, we evaluated the phylogenetic emergence of SCCmec V after transmission from overseas donor strains to Korean recipient strains.

METHODS: Sixty-three complete MRSA SCCmec V genomes (including six Korean clinical isolates) were used to construct a phylogenetic tree. Single-nucleotide polymorphisms were identified using Snippy, and a maximum-likelihood-based phylogenetic tree was constructed using RAxML. The possible emergence of the most common ancestor was estimated using BactDating. To estimate mecA horizontal gene transfer (HGT) events, Ranger-dtl was applied to 818 SCCmec V strains using publicly available whole-genome data.

RESULTS: The phylogenetic tree showed five major clades. German strains formed a major clade; their possible origin was traced to the 1980s. The emergence of Korean SCCmec V clinical isolates was traced to 2000-2010. mecA HGT events in Staphylococcus spp. were identified in seven strains. P7 (Hong Kong outbreak strain) served as the donor strain for two Korean sequence type (ST) 59 strains, whereas the other five recipient strains emerged from different SCCmec V donors.

CONCLUSIONS: Most Korean SCCmec V strains may have emerged during 2000-2010. A unique MRSA SCCmec V strain, ST72 (a Korean common type of community-associated MRSA), was also identified. The genomic dynamics of this clone with a zoonotic background should be monitored to accurately understand MRSA evolution.

RevDate: 2023-09-04

Mao C, Li Q, Komijani M, et al (2023)

Metagenomic analysis reveals the dissemination mechanisms and risks of resistance genes in plateau lakes.

iScience, 26(9):107508.

Antibiotic resistance genes (ARGs) are emerging as environmental pollutants that can persist and disseminate in aquatic environments. Lakes, as important sources of freshwater, also serve as potential natural reservoirs of ARGs. In this study, we analyzed the distribution and potential risks of resistance genes in five typical freshwater lakes on the Yunnan-Guizhou Plateau. Our findings revealed that multidrug and MLS ARGs dominated in the studied lakes. Notably, while Lugu Lake exhibited higher abundance of ARGs, mobile genetic elements (MGEs), and metal resistance genes (MRGs), a greater resistome risk was observed in the eutrophic Xingyun Lake. The dissemination processes of ARGs and MRGs are primarily driven by microbial communities and the horizontal gene transfer via MGEs. Limnohabitans, Flavobacterium, and Acinetobacter were identified as key players in the dissemination of ARGs. Our study highlights the persistence of ARGs and provides valuable baseline data and risk assessment of ARGs in plateau freshwater lakes.

RevDate: 2023-09-04

Jeong DE, Sundrani S, Hall RN, et al (2023)

DNA polymerase diversity reveals multiple incursions of Polintons during nematode evolution.

bioRxiv : the preprint server for biology pii:2023.08.22.554363.

Polintons are dsDNA, virus-like self-synthesizing transposons widely found in eukaryotic genomes. Recent metagenomic discoveries of Polinton-like viruses are consistent with the hypothesis that Polintons invade eukaryotic host genomes through infectious viral particles. Nematode genomes contain multiple copies of Polintons and provide an opportunity to explore the natural distribution and evolution of Polintons during this process. We performed an extensive search of Polintons across nematode genomes, identifying multiple full-length Polinton copies in several species. We provide evidence of both ancient Polinton integrations and recent mobility in strains of the same nematode species. In addition to the major nematode Polinton family, we identified a group of Polintons that are overall closely related to the major family, but encode a distinct protein-primed B family DNA polymerase (pPolB) that is related to homologs from a different group of Polintons present outside of the Nematoda . Phylogenetic analyses on the pPolBs support the evolutionary scenarios in which these extrinsic pPolBs that seem to derive from Polinton families present in oomycetes and molluscs replaced the canonical pPolB in subsets of Polintons found in terrestrial and marine nematodes, respectively, suggesting inter-phylum horizontal gene transfers. The pPolBs of the terrestrial nematode and oomycete Polintons share a unique feature, an insertion of a HNH nuclease domain, whereas the pPolBs in the marine nematode Polintons share an insertion of a VSR nuclease domain with marine mollusc pPolBs. We hypothesize that horizontal gene transfer occurs among Polintons from widely different but cohabiting hosts.

RevDate: 2023-09-04

Pandey T, Kalluraya C, Wang B, et al (2023)

Acquired stress resilience through bacteria-to-nematode horizontal gene transfer.

bioRxiv : the preprint server for biology pii:2023.08.20.554039.

Natural selection drives acquisition of organismal resilience traits to protect against adverse environments. Horizontal gene transfer (HGT) is an important evolutionary mechanism for the acquisition of novel traits, including metazoan acquisition of functions in immunity, metabolism, and reproduction via interdomain HGT (iHGT) from bacteria. We report that the nematode gene rml-3 , which was acquired by iHGT from bacteria, enables exoskeleton resilience and protection against environmental toxins in C. elegans . Phylogenetic analysis reveals that diverse nematode RML-3 proteins form a single monophyletic clade most highly similar to bacterial enzymes that biosynthesize L-rhamnose to build cell wall polysaccharides. C. elegans rml-3 is regulated in developing seam cells by heat stress and stress-resistant dauer stage. Importantly, rml-3 deficiency impairs cuticle integrity, barrier functions and organismal stress resilience, phenotypes that are rescued by exogenous L-rhamnose. We propose that iHGT of an ancient bacterial rml-3 homolog enables L-rhamnose biosynthesis in nematodes that facilitates cuticle integrity and organismal resilience in adaptation to environmental stresses during evolution. These findings highlight the remarkable contribution of iHGT on metazoan evolution that is conferred by the domestication of bacterial genes.

RevDate: 2023-09-04

Li Z, Zhou X, Liao D, et al (2023)

Comparative genomics and DNA methylation analysis of Pseudomonas aeruginosa clinical isolate PA3 by single-molecule real-time sequencing reveals new targets for antimicrobials.

Frontiers in cellular and infection microbiology, 13:1180194.

INTRODUCTION: Pseudomonas aeruginosa (P.aeruginosa) is an important opportunistic pathogen with broad environmental adaptability and complex drug resistance. Single-molecule real-time (SMRT) sequencing technique has longer read-length sequences, more accuracy, and the ability to identify epigenetic DNA alterations.

METHODS: This study applied SMRT technology to sequence a clinical strain P. aeruginosa PA3 to obtain its genome sequence and methylation modification information. Genomic, comparative, pan-genomic, and epigenetic analyses of PA3 were conducted.

RESULTS: General genome annotations of PA3 were discovered, as well as information about virulence factors, regulatory proteins (RPs), secreted proteins, type II toxin-antitoxin (TA) pairs, and genomic islands. A genome-wide comparison revealed that PA3 was comparable to other P. aeruginosa strains in terms of identity, but varied in areas of horizontal gene transfer (HGT). Phylogenetic analysis showed that PA3 was closely related to P. aeruginosa 60503 and P. aeruginosa 8380. P. aeruginosa's pan-genome consists of a core genome of roughly 4,300 genes and an accessory genome of at least 5,500 genes. The results of the epigenetic analysis identified one main methylation sites, N6-methyladenosine (m6A) and 1 motif (CATNNNNNNNTCCT/AGGANNNNNNNATG). 16 meaningful methylated sites were picked. Among these, purH, phaZ, and lexA are of great significance playing an important role in the drug resistance and biological environment adaptability of PA3, and the targeting of these genes may benefit further antibacterial studies.

DISUCSSION: This study provided a detailed visualization and DNA methylation information of the PA3 genome and set a foundation for subsequent research into the molecular mechanism of DNA methyltransferase-controlled P. aeruginosa pathogenicity.

RevDate: 2023-09-02

Clark JW (2023)

Genome evolution in plants and the origins of innovation.

The New phytologist [Epub ahead of print].

Plant evolution has been characterised by a series of major novelties in their vegetative and reproductive traits that have led to greater complexity. Underpinning this diversification has been the evolution of the genome. When viewed at the scale of the plant kingdom, plant genome evolution has been punctuated by conspicuous instances of gene and whole-genome duplication, horizontal gene transfer and extensive gene loss. The periods of dynamic genome evolution often coincide with the evolution of key traits, demonstrating the coevolution of plant genomes and phenotypes at a macroevolutionary scale. Conventionally, plant complexity and diversity have been considered through the lens of gene duplication and the role of gene loss in plant evolution remains comparatively unexplored. However, in light of reductive evolution across multiple plant lineages, the association between gene loss and plant phenotypic diversity warrants greater attention.

RevDate: 2023-09-01

Zhao Y, Hu Z, Xie H, et al (2023)

Size-dependent promotion of micro(nano)plastics on the horizontal gene transfer of antibiotic resistance genes in constructed wetlands.

Water research, 244:120520 pii:S0043-1354(23)00960-0 [Epub ahead of print].

Constructed wetlands (CWs) have been identified as significant sources of micro(nano)plastics (MPs/NPs) and antibiotic resistance genes (ARGs) in aquatic environments. However, little is known about the impact of MPs/NPs exposure on horizontal gene transfer (HGT) of ARGs and shaping the corresponding ARG hosts' community. Herein, the contribution of polystyrene (PS) particles (control, 4 mm, 100 μm, and 100 nm) to ARG transfer was investigated by adding an engineered fluorescent Escherichia coli harboring RP4 plasmid-encoded ARGs into CWs. It was found MPs/NPs significantly promoted ARG transfer in a size-dependent manner in each CW medium (p < 0.05). The 100 μm-sized PS exhibited the most significant promotion of ARG transfer (p < 0.05), whereas 100 nm-sized PS induced limited promotion due to its inhibitory activity on microbes. The altered RP4-carrying bacterial communities suggested that MPs/NPs, especially 100 µm-PS, could recruit pathogenic and nitrifying bacteria to acquire ARGs. The increased sharing of RP4-carrying core bacteria in CW medium further suggested that ARGs can spread into CW microbiome using MPs/NPs as carriers. Overall, our results highlight the high risks of ARG dissemination induced by MPs/NPs exposure and emphasize the need for better control of plastic disposal to prevent the potential health threats.

RevDate: 2023-08-31

Johnson ET, Bowman MJ, Gomes RP, et al (2023)

Identification of 2,4-diacetylphloroglucinol production in the genus Chromobacterium.

Scientific reports, 13(1):14292.

The compound 2,4-diacetylphloroglucinol (DAPG) is a broad-spectrum antibiotic that is primarily produced by Pseudomonas spp. DAPG plays an important role in the biocontrol disease suppressing activity of Pseudomonas spp. In the current study, we report the discovery of the DAPG biosynthetic cluster in strains of Chromobacterium vaccinii isolated from Brazilian aquatic environments and the distribution of the biosynthetic cluster in the Chromobacterium genus. Phylogenetic analysis of the phlD protein suggests the biosynthetic cluster probably entered the genus of Chromobacterium after a horizontal gene transfer event with a member of the Pseudomonas fluorescens group. We were able to detect trace amounts of DAPG in wild type cultures and confirm the function of the cluster with heterologous expression in Escherichia coli. In addition, we identified and verified the presence of other secondary metabolites in these strains. We also confirmed the ability of C. vaccinii strains to produce bioactive pigment violacein and bioactive cyclic depsipeptide FR900359. Both compounds have been reported to have antimicrobial and insecticidal activities. These compounds suggest strains of C. vaccinii should be further explored for their potential as biocontrol agents.

RevDate: 2023-08-31

Katsburg M, Brombach J, Hanke D, et al (2023)

New variant strain of Streptococcus canis with Lancefield group C isolated from canine otitis externa.

Veterinary microbiology, 285:109869 pii:S0378-1135(23)00221-3 [Epub ahead of print].

Every basic course in microbiology teaches us, Streptococcus canis always tests positive for Lancefield group G. Surprisingly, we identified a strain of S. canis with Lancefield group C, cultured from a dog with otitis externa after lateral ear canal resection. Whole genome sequencing data and analysis points towards a horizontal gene transfer event between S. canis and S. dysgalactiae. Although these species are closely related, gene transfer in this region of the genome of S. canis has not been described before. The value of technologies as MALDI-TOF MS and sequencing in microbiological diagnostics will grow as more diverse streptococci arise that do not always conform anymore to the classical Lancefield group typing.

RevDate: 2023-08-30

Ye J, Jin L, Li Y, et al (2023)

Complete-genome sequencing and comparative genomic characterization of blaNDM-5 carrying Citrobacter freundii isolates from a patient with multiple infections.

BMC genomics, 24(1):506.

BACKGROUND: The emergence and wide spread of carbapenemase-producing Enterobacteriaceae (CPE) poses a growing threat to global public health. However, clinically derived carbapenemase-producing Citrobacter causing multiple infections has rarely been investigated. Here we first report the isolation and comparative genomics of two blaNDM-5 carrying Citrobacter freundii (C. freundii) isolates from a patient with bloodstream and urinary tract infections.

RESULTS: Antimicrobial susceptibility testing showed that both blaNDM-5 carrying C. freundii isolates were multidrug-resistant. Positive modified carbapenem inactivation method (mCIM) and EDTA-carbapenem inactivation method (eCIM) results suggested metallo-carbapenemase production. PCR and sequencing confirmed that both metallo-carbapenemase producers were blaNDM-5 positive. Genotyping and comparative genomics analyses revealed that both isolates exhibited a high level of genetic similarity. Plasmid analysis confirmed that the blaNDM-5 resistance gene is located on IncX3 plasmid with a length of 46,161 bp, and could successfully be transferred to the recipient Escherichia coli EC600 strain. A conserved structure sequence (ISAba125-IS5-blaNDM-5-trpF-IS26-umuD-ISKox3) was found in the upstream and downstream of the blaNDM-5 gene.

CONCLUSIONS: The data presented in this study showed that the conjugative blaNDM-5 plasmid possesses a certain ability to horizontal transfer. The dissemination of NDM-5-producing C. freundii isolates should be of close concern in future clinical surveillance. To our knowledge, this is the first study to characterize C. freundii strains carrying the blaNDM-5 gene from one single patient with multiple infections.

RevDate: 2023-08-30

Goodman RN, Tansirichaiya S, AP Roberts (2023)

Development of pBACpAK entrapment vector derivatives to detect intracellular transfer of mobile genetic elements within chloramphenicol resistant bacterial isolates.

Journal of microbiological methods pii:S0167-7012(23)00147-1 [Epub ahead of print].

Antimicrobial resistance disseminates throughout bacterial populations via horizontal gene transfer, driven mainly by mobile genetic elements (MGEs). Entrapment vectors are key tools in determining MGE movement within a bacterial cell between different replicons or between sites within the same replicon. The pBACpAK entrapment vector has been previously used to study intracellular transfer in Gram-negative bacteria however since pBACpAK contains a chloramphenicol resistance gene, it cannot be used in bacterial isolates which are already resistant to chloramphenicol. Therefore, we developed new derivatives of the pBACpAK entrapment vector to determine intracellular transfer of MGEs in an Escherichia coli DH5α transconjugant containing the chloramphenicol resistance plasmid pD25466. The catA1 of pBACpAK was replaced by both mcr-1 in pBACpAK-COL and aph(3')-Ia in pBACpAK-KAN, allowing it to be used in chloramphenicol resistant strains. The plasmid constructs were verified and then used to transform the E. coli DH5α/pD25466 transconjugants in order to detect intracellular movement of the MGEs associated with the pD25466 plasmid. Here we report on the validation of the expanded suite of pBACpAK vectors which can be used to study the intracellular transfer of MGEs between, and within, replicons in bacteria with different antimicrobial resistance profiles.

RevDate: 2023-08-30

Xiong L, Li Y, Yu H, et al (2023)

Whole genome analysis and cold adaptation strategies of Pseudomonas sivasensis W-6 isolated from the Napahai plateau wetland.

Scientific reports, 13(1):14190.

Microbial communities of wetlands play key roles in the earth's ecology and stability. To elucidate the cold adaptation mechanisms of bacteria in plateau wetlands, we conducted comparative genomic analyses of Pseudomonas sivasensis and closely related lineages. The genome of P. sivasensis W-6, a cold-adapted bacterium isolated from the Napahai plateau wetland, was sequenced and analyzed. The genome length was 6,109,123 bp with a G+C content of 59.5%. Gene prediction yielded 5360 protein-coding sequences, 70 tRNAs, 24 gene islands, and 2 CRISPR sequences. The isolate contained evidence of horizontal gene transfer events during its evolution. Two prophages were predicted and indicated that W-6 was a lysogen. The cold adaptation of the W-6 strain showed psychrophilic rather than psychrotrophic characteristics. Cold-adapted bacterium W-6 can utilize glycogen and trehalose as resources, associated with carbohydrate-active enzymes, and survive in a low-temperature environment. In addition, the cold-adapted mechanisms of the W-6 included membrane fluidity by changing the unsaturated fatty acid profile, the two-component regulatory systems, anti-sense transcription, the role played by rpsU genes in the translation process, etc. The genome-wide analysis of W-6 provided a deeper understanding of cold-adapted strategies of bacteria in environments. We elucidated the adaptive mechanism of the psychrophilic W-6 strain for survival in a cold environment, which provided a basis for further study on host-phage coevolution.

RevDate: 2023-08-30

Youngblom MA, Imhoff MR, Smyth LM, et al (2023)

Portrait of a generalist bacterium: pathoadaptation, metabolic specialization and extreme environments shape diversity of Staphylococcus saprophyticus.

bioRxiv : the preprint server for biology pii:2023.08.18.553882.

UNLABELLED: Staphylococcus saprophyticus is a Gram-positive, coagulase-negative staphylococcus found in diverse environments including soil and freshwater, meat, and dairy foods. S. saprophyticus is also an important cause of urinary tract infections (UTIs) in humans, and mastitis in cattle. However, the genetic determinants of virulence have not yet been identified, and it remains unclear whether there are distinct sub-populations adapted to human and animal hosts. Using a diverse sample of S. saprophyticus isolates from food, animals, environmental sources, and human infections, we characterized the population structure and diversity of global populations of S. saprophyticus . We found that divergence of the two major clades of S. saprophyticus is likely facilitated by barriers to horizontal gene transfer (HGT) and differences in metabolism. Using genome-wide association study (GWAS) tools we identified the first Type VII secretion system (T7SS) described in S. saprophyticus and its association with bovine mastitis. Finally, we found that in general, strains of S. saprophyticus from different niches are genetically similar with the exception of built environments, which function as a 'sink' for S. saprophyticus populations. This work increases our understanding of the ecology of S. saprophyticus and of the genomics of bacterial generalists.

DATA SUMMARY: Raw sequencing data for newly sequenced S. saprophyticus isolates have been deposited to the NCBI SRA under the project accession PRJNA928770. A list of all genomes used in this work and their associated metadata are available in the supplementary material. Custom scripts used in the comparative genomics and GWAS analyses are available here: .

IMPACT STATEMENT: It is not known whether human and cattle diseases caused by S. saprophyticus represent spillover events from a generalist adapted to survive in a range of environments, or whether the capacity to cause disease represents a specific adaptation. Seasonal cycles of S. saprophyticus UTIs and molecular epidemiological evidence suggest that these infections may be environmentally-acquired rather than via transmission from person to person. Using comparative genomics and genome wide association study tools, we found that S. saprophyticus appears adapted to inhabit a wide range of environments (generalist), with isolates from animals, food, natural environments and human infections being closely related. Bacteria that routinely switch environments, particularly between humans and animals, are of particular concern when it comes to the spread of antibiotic resistance from farm environments into human populations. This work provides a framework for comparative genomic analyses of bacterial generalists and furthers our understanding of how bacterial populations move between humans, animals, and the environment.

RevDate: 2023-08-30

Lucero RM, Demirer K, Yeh TJ, et al (2023)

Transport of metformin metabolites by guanidinium exporters of the Small Multidrug Resistance family.

bioRxiv : the preprint server for biology pii:2023.08.10.552832.

UNLABELLED: Proteins from the Small Multidrug Resistance (SMR) family are frequently associated with horizontally transferred multidrug resistance gene arrays found in bacteria from wastewater and the human-adjacent biosphere. Recent studies suggest that a subset of SMR transporters might participate in metabolism of the common pharmaceutical metformin by bacterial consortia. Here, we show that both genomic and plasmid-associated transporters of the SMR Gdx functional subtype export byproducts of microbial metformin metabolism, with particularly high export efficiency for guanylurea. We use solid supported membrane electrophysiology to evaluate the transport kinetics for guanylurea and native substrate guanidinium by four representative SMR Gdx homologues. Using an internal reference to normalize independent electrophysiology experiments, we show that transport rates are comparable for genomic and plasmid-associated SMR Gdx homologues, and using a proteoliposome-based transport assay, we show that 2 proton:1 substrate transport stoichiometry is maintained. Additional characterization of guanidinium and guanylurea export properties focuses on the structurally characterized homologue, Gdx-Clo, for which we examined the pH dependence and thermodynamics of substrate binding and solved an x-ray crystal structure with guanylurea bound. Together, these experiments contribute in two main ways. By providing the first detailed kinetic examination of the structurally characterized SMR Gdx homologue Gdx-Clo, they provide a functional framework that will inform future mechanistic studies of this model transport protein. Second, this study casts light on a potential role for SMR Gdx transporters in microbial handling of metformin and its microbial metabolic byproducts, providing insight into how native transport physiologies are co-opted to contend with new selective pressures.

SUMMARY: Using solid supported membrane electrophysiology, structural biology, and binding assays, we characterize binding and transport of metformin metabolites by bacterial SMR transporters, including proteins associated with horizontal gene transfer in wastewater bacteria that degrade metformin.

RevDate: 2023-08-28

van Dijk B, Buffard P, Farr AD, et al (2023)

Identifying and tracking mobile elements in evolving compost communities yields insights into the nanobiome.

ISME communications, 3(1):90.

Microbial evolution is driven by rapid changes in gene content mediated by horizontal gene transfer (HGT). While mobile genetic elements (MGEs) are important drivers of gene flux, the nanobiome-the zoo of Darwinian replicators that depend on microbial hosts-remains poorly characterised. New approaches are necessary to increase our understanding beyond MGEs shaping individual populations, towards their impacts on complex microbial communities. A bioinformatic pipeline (xenoseq) was developed to cross-compare metagenomic samples from microbial consortia evolving in parallel, aimed at identifying MGE dissemination, which was applied to compost communities which underwent periodic mixing of MGEs. We show that xenoseq can distinguish movement of MGEs from demographic changes in community composition that otherwise confounds identification, and furthermore demonstrate the discovery of various unexpected entities. Of particular interest was a nanobacterium of the candidate phylum radiation (CPR) which is closely related to a species identified in groundwater ecosystems (Candidatus Saccharibacterium), and appears to have a parasitic lifestyle. We also highlight another prolific mobile element, a 313 kb plasmid hosted by a Cellvibrio lineage. The host was predicted to be capable of nitrogen fixation, and acquisition of the plasmid coincides with increased ammonia production. Taken together, our data show that new experimental strategies combined with bioinformatic analyses of metagenomic data stand to provide insight into the nanobiome as a driver of microbial community evolution.

RevDate: 2023-08-27

Zámocký M, P Feranc (2023)

Discovering the deep evolutionary roots of serum amyloid A protein family.

International journal of biological macromolecules pii:S0141-8130(23)03433-5 [Epub ahead of print].

Deep evolutionary origin of the conserved animal serum amyloid A (SAA) apolipoprotein family leading to yet unknown highly similar SAA-like sequences occurring in certain bacterial genomes is demonstrated in this contribution. Horizontal gene transfer event of corresponding genes between gut bacteria and non-vertebrate animals was discovered in the reconstructed phylogenetic tree obtained with maximum likelihood and neighbor-joining method, respectively. This detailed phylogeny based on totally 128 complete sequences comprised diverse serum amyloid A isoforms from various animal vertebrate and non-vertebrate phyla and also corresponding genes coding for highly similar proteins from animal gut bacteria. Typical largely conserved sequence motifs and a peculiar structural fold consisting mainly of four α-helix in a bundle within all reconstructed clades of the SAA protein family are discussed with respect to their supposed biological functions in various organisms that contain corresponding genes.

RevDate: 2023-08-26

Sabar MA, Van Huy T, Sugie Y, et al (2023)

Antimicrobial resistome and mobilome in the urban river affected by combined sewer overflows and wastewater treatment effluent.

Journal of water and health, 21(8):1032-1050.

The dissemination of antimicrobial resistance in the environment is an emerging global health problem. Wastewater treatment effluent and combined sewer overflows (CSOs) are major sources of antimicrobial resistance in urban rivers. This study aimed to clarify the effect of municipal wastewater treatment effluent and CSO on antimicrobial resistance genes (ARGs), mobile gene elements, and the microbial community in an urban river. The ARG abundance per 16S-based microbial population in the target river was 0.37-0.54 and 0.030-0.097 during the CSO event and dry weather, respectively. During the CSO event, the antimicrobial resistome in the river shifted toward a higher abundance of ARGs to clinically important drug classes, including macrolide, fluoroquinolone, and β-lactam, whereas ARGs to sulfonamide and multidrug by efflux pump were relatively abundant in dry weather. The abundance of intI1 and tnpA genes were highly associated with the total ARG abundance, suggesting their potential application as an indicator for estimating resistome contamination. Increase of prophage during the CSO event suggested that impact of CSO has a greater potential for horizontal gene transfer (HGT) via transduction. Consequently, CSO not only increases the abundance of ARGs to clinically important antimicrobials but also possibly enhances potential of HGT in urban rivers.

RevDate: 2023-08-26

Kozlova AP, Saksaganskaia AS, Afonin AM, et al (2023)

A Temperate Sinorhizobium Phage, AP-16-3, Closely Related to Phage 16-3: Mosaic Genome and Prophage Analysis.

Viruses, 15(8): pii:v15081701.

Soil Sinorhizobium phage AP-16-3, a strain phylogenetically close to Rhizobium phage 16-3, was isolated in a mountainous region of Dagestan, belonging to the origin of cultivated plants in the Caucasus, according to Vavilov N.I. The genome of phage AP-16-3 is 61 kbp in size and contains 62 ORFs, of which 42 ORFs have homologues in the genome of Rhizobium phage 16-3, which was studied in the 1960s-1980s. A search for Rhizobium phage 16-3-related sequences was performed in the genomes of modern strains of root nodule bacteria belonging to different species, genera, and families. A total of 43 prophages of interest were identified out of 437 prophages found in the genomes of 42 strains, of which 31 belonged to Sinorhizobium meliloti species. However, almost all of the mentioned prophages contained single ORFs, and only two prophages contained 51 and 39 ORFs homologous to phages related to 16-3. These prophages were detected in S. meliloti NV1.1.1 and Rh. leguminosarum OyaliB strains belonging to different genera; however, the similarity level of these two prophages did not exceed 14.7%. Analysis of the orphan genes in these prophages showed that they encoded predominantly virion structural elements, but also enzymes and an extensive group of hypothetical proteins belonging to the L, S, and E regions of viral genes of phage 16-3. The data obtained indicate that temperate phages related to 16-3 had high infectivity against nodule bacteria and participated in intragenomic recombination events involving other phages, and in horizontal gene transfer between rhizobia of different genera. According to the data obtained, it is assumed that the repetitive lysogenic cycle of temperate bacteriophages promotes the dissolution of the phage genetic material in the host bacterial genome, and radical updating of phage and host bacterial genomes takes place.

RevDate: 2023-08-26

Bonsaglia ECR, Calvo GH, Sordelli DO, et al (2023)

The Impact of Low-Level Benzalkonium Chloride Exposure on Staphylococcus spp. Strains and Control by Photoinactivation.

Antibiotics (Basel, Switzerland), 12(8): pii:antibiotics12081244.

Exposure of bacteria to low concentrations of biocides can facilitate horizontal gene transfer, which may lead to bacterial adaptive responses and resistance to antimicrobial agents. The emergence of antibacterial resistance not only poses a significant concern to the dairy industry but also adds to the complexity and cost of mastitis treatment. This study was aimed to evaluate how selective stress induced by benzalkonium chloride (BC) promotes antibiotic non-susceptibility in Staphylococcus spp. In addition, we investigated the efficacy of photodynamic inactivation (PDI) in both resistant and susceptible strains. The study determined the minimum inhibitory concentration (MIC) of BC using the broth microdilution method for different Staphylococcus strains. The experiments involved pairing strains carrying the qacA/qacC resistance genes with susceptible strains and exposing them to subinhibitory concentrations of BC for 72 h. The recovered isolates were tested for MIC BC and subjected to disc diffusion tests to assess changes in susceptibility patterns. The results demonstrated that subinhibitory concentrations of BC could select strains with reduced susceptibility and antibiotic resistance, particularly in the presence of S. pasteuri. The results of PDI mediated by toluidine blue (100 µM) followed by 60 min irradiation (total light dose of 2.5 J/cm[2]) were highly effective, showing complete inactivation for some bacterial strains and a reduction of up to 5 logs in others.

RevDate: 2023-08-24

Farrell AA, Nesbø CL, O Zhaxybayeva (2023)

Early divergence and gene exchange highways in the evolutionary history of Mesoaciditogales.

Genome biology and evolution pii:7250220 [Epub ahead of print].

The placement of a non-hyperthermophilic order Mesoaciditogales as the earliest branching clade within the Thermotogota phylum challenges the prevailing hypothesis that the last common ancestor of Thermotogota was a hyperthermophile. Yet, given the long branch leading to the only two Mesoaciditogales described to-date, the phylogenetic position of the order may be due to the long branch attraction artifact. By testing various models and applying data recoding in phylogenetic reconstructions, we observed that early branching of Mesoaciditogales within Thermotogota is strongly supported by the conserved marker genes assumed to be vertically inherited. However, based on the taxonomic content of 1,181 gene families and a phylogenetic analysis of 721 gene family trees, we also found that a substantial number of Mesoaciditogales genes are more closely related to species from the order Petrotogales. These genes contribute to coenzyme transport and metabolism, fatty acid biosynthesis, genes known to respond to heat and cold stressors, and include many genes of unknown functions. The Petrotogales comprise moderately thermophilic and mesophilic species with similar temperature tolerances to that of Mesoaciditogales. Our findings hint at extensive horizontal gene transfer between, or parallel independent gene gains by, the two ecologically similar lineages, and suggest that the exchanged genes may be important for adaptation to comparable temperature niches.

RevDate: 2023-08-23

Deng WK, He JL, Chen JY, et al (2023)

Effects of microplastics on functional genes related to CH4 and N2O metabolism in bacteriophages during manure composting and its planting applications.

Journal of hazardous materials, 460:132288 pii:S0304-3894(23)01571-6 [Epub ahead of print].

Microplastics (MPs), as a new type of pollutant, widely exist in livestock and poultry breeding and agricultural soils. However, research on MPs pollution on greenhouse gas emissions in combined planting and breeding systems is lacking, especially from the perspective of phage horizontal gene transfer. Therefore, this paper explores the effects of MPs on functional genes related to CH4 and N2O metabolism in bacteriophages during manure composting and its planting applications. The results of the study indicated that the addition of MPs had an impact on both the physicochemical properties and microbial community structure of manure during the composting process and on the compost-applied rhizosphere soil of lactuca (Lactuca sativa). Specifically, on day 7 of composting, mcrA/pmoA and (nirS+nirK) levels in bacteria in the MP group significantly increased. Additionally, it was observed that the MP group had higher average temperatures during the high-temperature period of composting, which led to a rapid reduction in phages. However, the phage levels quickly recovered during the cooling period. Furthermore, the addition of MPs to the rhizosphere soil resulted in higher levels of nirK. These changes may affect greenhouse gas emissions.

RevDate: 2023-08-23

Zhao Y, Kuang W, An Q, et al (2023)

Cryo-EM structures of African swine fever virus topoisomerase.

mBio [Epub ahead of print].

Type II topoisomerases ubiquitously exist in cellular organisms, where they play an essential role in resolving the topological problems of DNA. The viral type II topoisomerase encoded by the African swine fever virus (ASFV) is critical for viral replication and infection, thus representing an attractive target for antiviral drug development. Here we report two cryo-EM structures of ASFV topoisomerase P1192R in distinct conformations at an overall resolution of 3.16 Å and 3.13 Å, respectively. P1192R assembles as a homodimer with the C-gate formed by the coiled-coil domain adopting a closed or open conformation before reaction, providing the first visual evidence for the dynamic motions of the C-gate of type II topoisomerase. Comparative structural comparisons of eukaryotic homologs and P1192R reveal the unique structural features of P1192R, including the active site configuration, a flexible loop in the TOPRIM domain, an additionally inserted α-helix in the tower domain, and a pin-like structure in the C-terminal coiled-coil domain, which are important for enzyme activity and protein folding. These findings provide important insights into the structure and function of viral topoisomerases and may guide the efficient development of anti-ASFV drugs. Moreover, our study also offers structural evidence to support the scenario of the viral origin of eukaryotic type IIA topoisomerases. IMPORTANCE African swine fever virus (ASFV) is a highly contagious virus that causes lethal hemorrhagic diseases known as African swine fever (ASF) with a case fatality rate of 100%. There is an urgent need to develop anti-ASFV drugs. We determine the first high-resolution structures of viral topoisomerase ASFV P1192R in both the closed and open C-gate forms. P1192R shows a similar overall architecture with eukaryotic and prokaryotic type II topoisomerases, which have been successful targets of many antimicrobials and anticancer drugs, with the most similarity to yeast topo II. P1192R also exhibits differences in the details of active site configuration, which are important to enzyme activity. These two structures offer useful structural information for antiviral drug design and provide structural evidence to support that eukaryotic type IIA topoisomerase likely originated from horizontal gene transfer from the virus.

RevDate: 2023-08-23

Hsu TY, Nzabarushimana E, Wong D, et al (2023)

Profiling novel lateral gene transfer events in the human microbiome.

bioRxiv : the preprint server for biology pii:2023.08.08.552500.

Lateral gene transfer (LGT) is an important mechanism for genome diversification in microbial populations, including the human microbiome. While prior work has surveyed LGT events in human-associated microbial isolate genomes, the scope and dynamics of novel LGT events arising in personal microbiomes are not well understood, as there are no widely adopted computational methods to detect, quantify, and characterize LGT from complex microbial communities. We addressed this by developing, benchmarking, and experimentally validating a computational method (WAAFLE) to profile novel LGT events from assembled metagenomes. Applying WAAFLE to >2K human metagenomes from diverse body sites, we identified >100K putative high-confidence but previously uncharacterized LGT events (∼2 per assembled microbial genome-equivalent). These events were enriched for mobile elements (as expected), as well as restriction-modification and transport functions typically associated with the destruction of foreign DNA. LGT frequency was quantifiably influenced by biogeography, the phylogenetic similarity of the involved taxa, and the ecological abundance of the donor taxon. These forces manifest as LGT networks in which hub species abundant in a community type donate unequally with their close phylogenetic neighbors. Our findings suggest that LGT may be a more ubiquitous process in the human microbiome than previously described. The open-source WAAFLE implementation, documentation, and data from this work are available at .

RevDate: 2023-08-21

Baig MIR, Kadu P, Bawane P, et al (2023)

Mechanisms of emerging resistance associated with non-antibiotic antimicrobial agents: a state-of-the-art review.

The Journal of antibiotics [Epub ahead of print].

Although the development of resistance by microorganisms to antimicrobial drugs has been recognized as a global public health concern, the contribution of various non-antibiotic antimicrobial agents to the development of antimicrobial resistance (AMR) remains largely neglected. The present review discusses various chemical substances and factors other than typical antibiotics, such as preservatives, disinfectants, biocides, heavy metals and improper chemical sterilization that contribute to the development of AMR. Furthermore, it encompasses the mechanisms like co-resistance and co-selection, horizontal gene transfer, changes in the composition and permeability of cell membrane, efflux pumps, transposons, biofilm formation and enzymatic degradation of antimicrobial chemicals which underlie the development of resistance to various non-antibiotic antimicrobial agents. In addition, the review addresses the resistance-associated changes that develops in microorganisms due to these agents, which ultimately contribute to the development of resistance to antibiotics. In order to prevent the indiscriminate use of chemical substances and create novel therapeutic agents to halt resistance development, a more holistic scientific approach might provide diversified views on crucial factors contributing to the persistence and spread of AMR. The review illustrates the common and less explored mechanisms contributing directly or indirectly to the development of AMR by non-antimicrobial agents that are commonly used.

RevDate: 2023-08-18

Kobayashi N, Dang TA, Kieu PTM, et al (2023)

Horizontally transferred DNA in the genome of the fungus Pyricularia oryzae is associated with repressive histone modifications.

Molecular biology and evolution pii:7245980 [Epub ahead of print].

Horizontal gene transfer (HGT) is a means of exchanging genetic material asexually. The process by which horizontally transferred genes are domesticated by the host genome is of great interest but is not well understood. In this study, we determined the telomere-to-telomere genome sequence of the wheat-infecting Pyricularia oryzae strain Br48. SNP analysis indicated that the Br48 strain is a hybrid of wheat- and Brachiaria-infecting strains by a sexual or parasexual cross. Comparative genomic analysis identified several megabase-scale "insertions" in the Br48 genome, some of which were possibly gained by HGT-related events from related species, such as P. pennisetigena or P. grisea. Notably, the mega-insertions often contained genes whose phylogeny is not congruent with the species phylogeny. Moreover, some of the genes have a close homolog even in distantly related organisms, such as basidiomycetes or prokaryotes, implying the involvement of multiple HGT events. Interestingly, the levels of the silent epigenetic marks H3K9me3 and H3K27me3 in a genomic region, tended to be negatively correlated with the phylogenetic concordance of genes in the same region, suggesting that horizontally transferred DNA is preferentially targeted for epigenetic silencing. Indeed, the putative HGT-derived genes were activated when MoKmt6, the gene responsible for H3K27me3 modification, was deleted. Notably, these genes also tended to be up-regulated during infection, suggesting that they are now under host control and has contributed to establishing a fungal niche. In conclusion, this study suggests that epigenetic modifications have played an important role in the domestication of HGT-derived genes in the P. oryzae genome.

RevDate: 2023-08-18

Yang C, Xiang Y, S Qiu (2023)

Resistance in Enteric Shigella and nontyphoidal Salmonella: emerging concepts.

Current opinion in infectious diseases pii:00001432-990000000-00096 [Epub ahead of print].

PURPOSE OF REVIEW: The emergence of globally resistant enteric Shigella and nontyphoidal Salmonella strains (NTS) has limited the selection of effective drugs, which has become a major challenge for the treatment of infections. The purpose of this review is to provide the current opinion on the antimicrobial-resistant enteric Shigella and nontyphoidal Salmonella.

RECENT FINDINGS: Enteric Shigella and NTS are resistant to almost all classes of antimicrobials in recent years. Those with co-resistance to ciprofloxacin, azithromycin and ceftriaxone, the first-line antibiotics for the treatment of infectious diarrhoea have emerged worldwide. Some of them have caused interregional and international spread by travel, trade, MSM, and polluted water sources. Several strains have even developed resistance to colistin, the last-resort antibiotic used for treatment of multidrug-resistant Gram-negative bacteria infections.

SUMMARY: The drug resistance of enteric Shigella and NTS is largely driven by the use of antibiotics and horizontal gene transfer of mobile genetic elements. These two species show various drug resistance patterns in different regions and serotypes. Hence treatment decisions for Shigella and Salmonella infections need to take into consideration prevalent antimicrobial drug resistance patterns. It is worth noting that the resistance genes such as blaCTX,mph, ermB, qnr and mcr, which can cause resistance to ciprofloxacin, cephalosporin, azithromycin and colistin are widespread because of transmission by IncFII, IncI1, IncI2 and IncB/O/K/Z plasmids. Therefore, continuous global monitoring of resistance in Shigella and Salmonella is imperative.

RevDate: 2023-08-18
CmpDate: 2023-08-18

Huang J, Dai X, Wu Z, et al (2023)

Conjugative transfer of streptococcal prophages harboring antibiotic resistance and virulence genes.

The ISME journal, 17(9):1467-1481.

Prophages play important roles in the transduction of various functional traits, including virulence factors, but remain debatable in harboring and transmitting antimicrobial resistance genes (ARGs). Herein we characterize a prevalent family of prophages in Streptococcus, designated SMphages, which harbor twenty-five ARGs that collectively confer resistance to ten antimicrobial classes, including vanG-type vancomycin resistance locus and oxazolidinone resistance gene optrA. SMphages integrate into four chromosome attachment sites by utilizing three types of integration modules and undergo excision in response to phage induction. Moreover, we characterize four subtypes of Alp-related surface proteins within SMphages, the lethal effects of which are extensively validated in cell and animal models. SMphages transfer via high-frequency conjugation that is facilitated by integrative and conjugative elements from either donors or recipients. Our findings explain the widespread of SMphages and the rapid dissemination of ARGs observed in members of the Streptococcus genus.

RevDate: 2023-08-17

Zhang X, Xiao L, Liu J, et al (2023)

Trade-off in genome turnover events leading to adaptive evolution of Microcystis aeruginosa species complex.

BMC genomics, 24(1):462.

BACKGROUND: Numerous studies in the past have expanded our understanding of the genetic differences of global distributed cyanobacteria that originated around billions of years ago, however, unraveling how gene gain and loss drive the genetic evolution of cyanobacterial species, and the trade-off of these evolutionary forces are still the central but poorly understood issues.

RESULTS: To delineate the contribution of gene flow in mediating the hereditary differentiation and shaping the microbial evolution, a global genome-wide study of bloom-forming cyanobacterium, Microcystis aeruginosa species complex, provided robust evidence for genetic diversity, reflected by enormous variation in gene repertoire among various strains. Mathematical extrapolation showed an 'open' microbial pan-genome of M. aeruginosa species, since novel genes were predicted to be introduced after new genomes were sequenced. Identification of numerous horizontal gene transfer's signatures in genome regions of interest suggested that genome expansion via transformation and phage-mediated transduction across bacterial lineage as an evolutionary route may contribute to the differentiation of Microcystis functions (e.g., carbohydrate metabolism, amino acid metabolism, and energy metabolism). Meanwhile, the selective loss of some dispensable genes at the cost of metabolic versatility is as a mean of adaptive evolution that has the potential to increase the biological fitness.

CONCLUSIONS: Now that the recruitment of novel genes was accompanied by a parallel loss of some other ones, a trade-off in gene content may drive the divergent differentiation of M. aeruginosa genomes. Our study provides a genetic framework for the evolution of M. aeruginosa species and illustrates their possible evolutionary patterns.

RevDate: 2023-08-16

Shen C, He M, Zhang J, et al (2023)

Effects of the coexistence of antibiotics and heavy metals on the fate of antibiotic resistance genes in chicken manure and surrounding soils.

Ecotoxicology and environmental safety, 263:115367 pii:S0147-6513(23)00871-0 [Epub ahead of print].

Both heavy metals and antibiotics exert selection pressure on bacterial resistance, and as they are commonly co-contaminated in the environment, they may play a larger role in bacterial resistance. This study examined how breeding cycles affect antibiotic resistance genes (ARGs) in chicken manure and the surrounding topsoils at 20, 50, 100, 200, and 300 m from twelve typical laying hen farms in the Ningxia Hui Autonomous Region of northwest China. Six antibiotics, seven heavy metals, ten mobile genetic elements (MGEs), and microbial community affected the ARGs profile in chicken dung and soil samples. Tetracycline antibiotic residues were prevalent in chicken manure, as were relatively high content of aureomycin during each culture period. Zinc (Zn) content was highest among the seven heavy metals in chicken feces. Chicken dung also enriched aminoglycosides, MLSB, and tetracycline ARGs, notably during brooding and high production. The farm had a minimal influence on antibiotics in the surrounding soil, but its effect on ARGs and MGEs closer to the farm (50 m) was stronger, and several ARGs and MGEs increased with distance. Manure microbial composition differed dramatically throughout breeding cycles and sampling distances. ARGs were more strongly related with antibiotics and heavy metals in manure than soil, whereas MGEs were the reverse. Antibiotics, heavy metals, MGEs, and bacteria in manure accounted 12.28%, 22.25%, 0.74%, and 0.19% of ARGs composition variance, respectively, according to RDA and VPA. Bacteria (2.89%) and MGEs (2.82%) only affected soil ARGs composition. These findings showed that heavy metals and antibiotics are the main factors affecting faecal ARGs and bacteria and MGEs soil ARGs. This paper includes antibiotic resistance data for large-scale laying hen husbandry in northwest China and a theoretical framework for decreasing antibiotic resistance.

RevDate: 2023-08-16

Mi-Ichi F, Tsugawa H, Yoshida H, et al (2023)

Unique features of Entamoeba histolytica glycerophospholipid metabolism; has the E. histolytica lipid metabolism network evolved through gene loss and gain to enable parasitic life cycle adaptation?.

mSphere [Epub ahead of print].

Entamoeba histolytica, a protozoan parasite, causes amoebiasis, which is a global public health problem. During the life cycle of this parasite, the properties of the cell membrane are changed markedly. To clarify the mechanism of membrane lipid changes, we exploited state-of-the-art untargeted lipidomic analysis, and atypical features of glycerophospholipids, lysoglycerophospholipids, and sphingolipids were observed compared with human equivalents. Here, we overview an entire E. histolytica glycerophospholipid metabolic pathway based on re-evaluated whole lipidome and genome along with the results of metabolic labeling experiments. We also discuss whether the E. histolytica lipid metabolism network, including the glycerophospholipid metabolic pathway, has unique features necessary for parasitic life cycle adaptation through gene loss and/or gain, and raise important questions involving biochemistry, molecular cell biology, and physiology underlying this network. Answering these questions will advance the understanding of Entamoeba physiology and will provide potential targets to develop new anti-amoebiasis drugs.

RevDate: 2023-08-16

Boyer C, Lefeuvre P, Richard D, et al (2023)

Complete genome sequence of a copper-resistant Xanthomonas campestris pv. campestris strain isolated from broccoli in Mauritius suggests adaptive gene gain through horizontal gene transfer.

Phytopathology [Epub ahead of print].

Bacterial adaptation is facilitated by the presence of mobile genetic elements (MGEs) and horizontal gene transfer (HGT) of genes, such as those coding for virulence factors or resistance to antimicrobial compounds. A hybrid assembly of Nanopore MinIon long read and Illumina short read data was produced from a copper-resistant Xanthomonas campestris pv. campestris (Xcc) strain isolated from symptomatic broccoli leaves in Mauritius. We obtained a 5.2 Mb high-quality chromosome and no plasmid. We found four genomic islands, three of which were characterized as integrative conjugative elements or integrative mobilizable elements. These genomic islands carried type III effectors and the copper resistance copLABMGF system involved in pathogenicity and environmental adaptation, respectively.

RevDate: 2023-08-15

Anonymous (2023)

Horizontal gene transfer explains unusual traits of Armillaria fungi.

Nature microbiology [Epub ahead of print].

RevDate: 2023-08-15
CmpDate: 2023-08-15

Kelleher ES (2023)

Jack of all trades versus master of one: how generalist versus specialist strategies of transposable elements relate to their horizontal transfer between lineages.

Current opinion in genetics & development, 81:102080.

Transposable elements (TEs) are obligate genomic parasites, relying on host germline cells to ensure their replication and passage to future generations. While some TEs exhibit high fidelity to their host genome, being passed from parent to offspring through vertical transmission for millions of years, others frequently invade new and distantly related hosts through horizontal transfer. In this review, I highlight how the complexity of interactions between TE and host required for transposition may be an important determinant of horizontal transfer: with TEs with more complex regulatory requirements being less able to invade new host genomes.

RevDate: 2023-08-14

Luo G, Liang B, Cui H, et al (2023)

Determining the Contribution of Micro/Nanoplastics to Antimicrobial Resistance: Challenges and Perspectives.

Environmental science & technology [Epub ahead of print].

Microorganisms colonizing the surfaces of microplastics form a plastisphere in the environment, which captures miscellaneous substances. The plastisphere, owning to its inherently complex nature, may serve as a "Petri dish" for the development and dissemination of antibiotic resistance genes (ARGs), adding a layer of complexity in tackling the global challenge of both microplastics and ARGs. Increasing studies have drawn insights into the extent to which the proliferation of ARGs occurred in the presence of micro/nanoplastics, thereby increasing antimicrobial resistance (AMR). However, a comprehensive review is still lacking in consideration of the current increasingly scattered research focus and results. This review focuses on the spread of ARGs mediated by microplastics, especially on the challenges and perspectives on determining the contribution of microplastics to AMR. The plastisphere accumulates biotic and abiotic materials on the persistent surfaces, which, in turn, offers a preferred environment for gene exchange within and across the boundary of the plastisphere. Microplastics breaking down to smaller sizes, such as nanoscale, can possibly promote the horizontal gene transfer of ARGs as environmental stressors by inducing the overgeneration of reactive oxygen species. Additionally, we also discussed methods, especially quantitatively comparing ARG profiles among different environmental samples in this emerging field and the challenges that multidimensional parameters are in great necessity to systematically determine the antimicrobial dissemination risk in the plastisphere. Finally, based on the biological sequencing data, we offered a framework to assess the AMR risks of micro/nanoplastics and biocolonizable microparticles that leverage multidimensional AMR-associated messages, including the ARGs' abundance, mobility, and potential acquisition by pathogens.

RevDate: 2023-08-14

Wolters JF, LaBella AL, Opulente DA, et al (2023)

Mitochondrial Genome Diversity across the Subphylum Saccharomycotina.

bioRxiv : the preprint server for biology pii:2023.07.28.551029.

Eukaryotic life depends on the functional elements encoded by both the nuclear genome and organellar genomes, such as those contained within the mitochondria. The content, size, and structure of the mitochondrial genome varies across organisms with potentially large implications for phenotypic variance and resulting evolutionary trajectories. Among yeasts in the subphylum Saccharomycotina, extensive differences have been observed in various species relative to the model yeast Saccharomyces cerevisiae , but mitochondrial genome sampling across many groups has been scarce, even as hundreds of nuclear genomes have become available. By extracting mitochondrial assemblies from existing short-read genome sequence datasets, we have greatly expanded both the number of available genomes and the coverage across sparsely sampled clades. Comparison of 353 yeast mitochondrial genomes revealed that, while size and GC content were fairly consistent across species, those in the genera Metschnikowia and Saccharomyces trended larger, while several species in the order Saccharomycetales, which includes S. cerevisiae , exhibited lower GC content. Extreme examples for both size and GC content were scattered throughout the subphylum. All mitochondrial genomes shared a core set of protein-coding genes for Complexes III, IV, and V, but they varied in the presence or absence of mitochondrially-encoded canonical Complex I genes. We traced the loss of Complex I genes to a major event in the ancestor of the orders Saccharomycetales and Saccharomycodales, but we also observed several independent losses in the orders Phaffomycetales, Pichiales, and Dipodascales. In contrast to prior hypotheses based on smaller-scale datasets, comparison of evolutionary rates in protein-coding genes showed no bias towards elevated rates among aerobically fermenting (Crabtree/Warburg-positive) yeasts. Mitochondrial introns were widely distributed, but they were highly enriched in some groups. The majority of mitochondrial introns were poorly conserved within groups, but several were shared within groups, between groups, and even across taxonomic orders, which is consistent with horizontal gene transfer, likely involving homing endonucleases acting as selfish elements. As the number of available fungal nuclear genomes continues to expand, the methods described here to retrieve mitochondrial genome sequences from these datasets will prove invaluable to ensuring that studies of fungal mitochondrial genomes keep pace with their nuclear counterparts.

RevDate: 2023-08-14

Bonatelli ML, Rohwerder T, Popp D, et al (2023)

Recently evolved combination of unique sulfatase and amidase genes enables bacterial degradation of the wastewater micropollutant acesulfame worldwide.

Frontiers in microbiology, 14:1223838.

Xenobiotics often challenge the principle of microbial infallibility. One example is acesulfame introduced in the 1980s as zero-calorie sweetener, which was recalcitrant in wastewater treatment plants until the early 2010s. Then, efficient removal has been reported with increasing frequency. By studying acesulfame metabolism in alphaproteobacterial degraders of the genera Bosea and Chelatococcus, we experimentally confirmed the previously postulated route of two subsequent hydrolysis steps via acetoacetamide-N-sulfonate (ANSA) to acetoacetate and sulfamate. Genome comparison of wildtype Bosea sp. 100-5 and an acesulfame degradation-defective mutant revealed the involvement of two plasmid-borne gene clusters. The acesulfame-hydrolyzing sulfatase is strictly manganese-dependent and belongs to the metallo beta-lactamase family. In all degraders analyzed, it is encoded on a highly conserved gene cluster embedded in a composite transposon. The ANSA amidase, on the other hand, is an amidase signature domain enzyme encoded in another gene cluster showing variable length among degrading strains. Transposition of the sulfatase gene cluster between chromosome and plasmid explains how the two catabolic gene clusters recently combined for the degradation of acesulfame. Searching available genomes and metagenomes for the two hydrolases and associated genes indicates that the acesulfame plasmid evolved and spread worldwide in short time. While the sulfatase is unprecedented and unique for acesulfame degraders, the amidase occurs in different genetic environments and likely evolved for the degradation of other substrates. Evolution of the acesulfame degradation pathway might have been supported by the presence of structurally related natural and anthropogenic compounds, such as aminoacyl sulfamate ribonucleotide or sulfonamide antibiotics.

RevDate: 2023-08-14

Chandler M, Ross K, AM Varani (2023)

The insertion sequence excision enhancer: A PrimPol-based primer invasion system for immobilizing transposon-transmitted antibiotic resistance genes.

Molecular microbiology [Epub ahead of print].

Evolutionary studies often identify genes that have been exchanged between different organisms and the phrase Lateral or Horizontal Gene Transfer is often used in this context. However, they rarely provide any mechanistic information concerning how these gene transfers might have occurred. With the astonishing increase in the number of sequences in public databases over the past two or three decades, identical antibiotic resistance genes have been identified in many different sequence contexts. One explanation for this would be that genes are initially transmitted by transposons which have subsequently decayed and can no longer be detected. Here, we provide an overview of a protein, IEE (Insertion Sequence Excision Enhancer) observed to facilitate high-frequency excision of IS629 from clinically important Escherichia coli O157:H7 and subsequently shown to affect a large class of bacterial insertion sequences which all transpose using the copy-out-paste-in transposition mechanism. Excision depends on both IEE and transposase indicating association with the transposition process itself. We review genetic and biochemical data and propose that IEE immobilizes genes carried by compound transposons by removing the flanking insertion sequence (IS) copies. The biochemical activities of IEE as a primase with the capacity to recognize DNA microhomologies and the observation that its effect appears restricted to IS families which use copy-out-paste-in transposition, suggests IS deletion occurs by abortive transposition involving strand switching (primer invasion) during the copy-out step. This reinforces the proposal made for understanding the widespread phenomenon loss of ISApl1 flanking mcr-1 in the compound transposon Tn6330 which we illustrate with a detailed model. This model also provides a convincing way to explain the high levels of IEE-induced precise IS excision.

RevDate: 2023-08-11

Andrade-Oliveira AL, Rodrigues GL, Pereira MF, et al (2023)

Tenebrio molitor as a model system to study Staphylococcus spp virulence and horizontal gene transfer.

Microbial pathogenesis pii:S0882-4010(23)00337-6 [Epub ahead of print].

Invertebrates can provide a valuable alternative to traditional vertebrate animal models for studying bacterial and fungal infections. This study aimed to establish the larvae of the coleoptera Tenebrio molitor (mealworm) as an in vivo model for evaluating virulence and horizontal gene transfer between Staphylococcus spp. After identifying the best conditions for rearing T. molitor, larvae were infected with different Staphylococcus species, resulting in dose-dependent killing curves. All species tested killed the insects at higher doses, with S. nepalensis and S. aureus being the most and least virulent, respectively. However, only S. nepalensis was able to kill more than 50% of larvae 72 h post-infection at a low amount of 10[5] CFU. Staphylococcus infection also stimulated an increase in the concentration of hemocytes present in the hemolymph, which was proportional to the virulence. To investigate T. molitor's suitability as an in vivo model for plasmid transfer studies, we used S. aureus strains as donor and recipient of a plasmid containing the gentamicin resistance gene aac(6')-aph(2″). By inoculating larvae with non-lethal doses of each, we observed conjugation, and obtained transconjugant colonies with a frequency of 1.6 × 10[-5] per donor cell. This study demonstrates the potential of T. molitor larvae as a reliable and cost-effective model for analyzing the virulence of Staphylococcus and, for the first time, an optimal environment for the plasmid transfer between S. aureus carrying antimicrobial resistance genes.

RevDate: 2023-08-11

Yin L, Wang X, Xu H, et al (2023)

Unrecognized risk of perfluorooctane sulfonate in promoting conjugative transfers of bacterial antibiotic resistance genes.

Applied and environmental microbiology [Epub ahead of print].

Antibiotic resistance is a major global health crisis facing humanity, with horizontal gene transfer (HGT) as a principal dissemination mechanism in the natural and clinical environments. Perfluoroalkyl substances (PFASs) are emerging contaminants of global concern due to their high persistence in the environment and adverse effects on humans. However, it is unknown whether PFASs affect the HGT of bacterial antibiotic resistance. Using a genetically engineered Escherichia coli MG1655 as the donor of plasmid-encoded antibiotic resistance genes (ARGs), E. coli J53 and soil bacterial community as two different recipients, this study demonstrated that the conjugation frequency of ARGs between two E. coli strains was (1.45 ± 0.17) × 10[-5] and perfluorooctane sulfonate (PFOS) at environmentally relevant concentrations (2-50 μg L[-1]) increased conjugation transfer between E. coli strains by up to 3.25-fold. Increases in reactive oxygen species production, cell membrane permeability, biofilm formation capacity, and cell contact in two E. coli strains were proposed as major promotion mechanisms from PFOS exposure. Weighted gene co-expression network analysis of transcriptome data identified a series of candidate genes whose expression changes could contribute to the increase in conjugation transfer induced by PFOS. Furthermore, PFOS also generally increased the ARG transfer into the studied soil bacterial community, although the uptake ability of different community members of the plasmid either increased or decreased upon PFOS exposure depending on specific bacterial taxa. Overall, this study reveals an unrecognized risk of PFOS in accelerating the dissemination of antibiotic resistance. IMPORTANCE Perfluoroalkyl substances (PFASs) are emerging contaminants of global concern due to their high persistence in the environment and adverse health effects. Although the influence of environmental pollutants on the spread of antibiotic resistance, one of the biggest threats to global health, has attracted increasing attention in recent years, it is unknown whether environmental residues of PFASs affect the dissemination of bacterial antibiotic resistance. Considering PFASs, often called "forever" compounds, have significantly higher environmental persistence than most emerging organic contaminants, exploring the effect of PFASs on the spread of antibiotic resistance is more environmentally relevant and has essential ecological and health significance. By systematically examining the influence of perfluorooctane sulfonate on the antibiotic resistance gene conjugative transfer, not only at the single-strain level but also at the community level, this study has uncovered an unrecognized risk of PFASs in promoting conjugative transfers of bacterial antibiotic resistance genes, which could be incorporated into the risk assessment framework of PFASs.

RevDate: 2023-08-11

Gulay A, Fournier G, Smets BF, et al (2023)

Proterozoic Acquisition of Archaeal Genes for Extracellular Electron Transfer: A Metabolic Adaptation of Aerobic Ammonia-Oxidizing Bacteria to Oxygen Limitation.

Molecular biology and evolution, 40(8):.

Many aerobic microbes can utilize alternative electron acceptors under oxygen-limited conditions. In some cases, this is mediated by extracellular electron transfer (or EET), wherein electrons are transferred to extracellular oxidants such as iron oxide and manganese oxide minerals. Here, we show that an ammonia-oxidizer previously known to be strictly aerobic, Nitrosomonas communis, may have been able to utilize a poised electrode to maintain metabolic activity in anoxic conditions. The presence and activity of multiheme cytochromes in N. communis further suggest a capacity for EET. Molecular clock analysis shows that the ancestors of β-proteobacterial ammonia oxidizers appeared after Earth's atmospheric oxygenation when the oxygen levels were >10-4pO2 (present atmospheric level [PAL]), consistent with aerobic origins. Equally important, phylogenetic reconciliations of gene and species trees show that the multiheme c-type EET proteins in Nitrosomonas and Nitrosospira lineages were likely acquired by gene transfer from γ-proteobacteria when the oxygen levels were between 0.1 and 1 pO2 (PAL). These results suggest that β-proteobacterial EET evolved during the Proterozoic when oxygen limitation was widespread, but oxidized minerals were abundant.

RevDate: 2023-08-10

Cooper RM, Wright JA, Ng JQ, et al (2023)

Engineered bacteria detect tumor DNA.

Science (New York, N.Y.), 381(6658):682-686.

Synthetic biology has developed sophisticated cellular biosensors to detect and respond to human disease. However, biosensors have not yet been engineered to detect specific extracellular DNA sequences and mutations. Here, we engineered naturally competent Acinetobacter baylyi to detect donor DNA from the genomes of colorectal cancer (CRC) cells, organoids, and tumors. We characterized the functionality of the biosensors in vitro with coculture assays and then validated them in vivo with sensor bacteria delivered to mice harboring colorectal tumors. We observed horizontal gene transfer from the tumor to the sensor bacteria in our mouse model of CRC. This cellular assay for targeted, CRISPR-discriminated horizontal gene transfer (CATCH) enables the biodetection of specific cell-free DNA.

RevDate: 2023-08-09

Weaver RJ, AE McDonald (2023)

Mitochondrial alternative oxidase across the tree of life: Presence, absence, and putative cases of lateral gene transfer.

Biochimica et biophysica acta. Bioenergetics pii:S0005-2728(23)00049-X [Epub ahead of print].

The alternative oxidase (AOX) is a terminal oxidase in the electron transport system that plays a role in mitochondrial bioenergetics. The past 20 years of research shows AOX has a wide yet patchy distribution across the tree of life. AOX has been suggested to have a role in stress tolerance, growth, and development in plants, but less is known about its function in other groups, including animals. In this study, we analyzed the taxonomic distribution of AOX across >2800 species representatives from prokaryotes and eukaryotes and developed a standardized workflow for finding and verifying the authenticity of AOX sequences. We found that AOX is limited to proteobacteria among prokaryotes, but is widely distributed in eukaryotes, with the highest prevalence in plants, fungi, and protists. AOX is present in many invertebrates, but is absent in others including most arthropods, and is absent from vertebrates. We found aberrant AOX sequences associated with some animal groups. Some of these aberrant AOXs were contaminants, but we also found putative cases of lateral gene transfer of AOX from fungi and protists to nematodes, springtails, fungus gnats, and rotifers. Our findings provide a robust and detailed analysis of the distribution of AOX and a method for identifying and verifying putative AOX sequences, which will be useful as more sequence data becomes available on public repositories.

RevDate: 2023-08-09

Veremeichik GN, Gorpenchenko TY, Rusapetova TV, et al (2023)

Auxin-dependent regulation of growth via rolB-induced modulation of the ROS metabolism in the long-term cultivated pRiA4-transformed Rubiacordifolia L. calli.

Plant physiology and biochemistry : PPB, 202:107932 pii:S0981-9428(23)00443-6 [Epub ahead of print].

Gene transfer from Agrobacterium to plants is the best studied example of horizontal gene transfer (HGT) between prokaryotes and eukaryotes. The rol genes of A. rhizogenes (Rhizobium rhizogenes) provide uncontrolled root growth, or "hairy root" syndrome, the main diagnostic feature. In the present study, we investigated the stable pRiA4-transformed callus culture of Rubia cordifolia L. While untransformed callus cultures need PGRs (plant growth regulators) as an obligatory supplement, pRiA4 calli is able to achieve long-term PGR-free cultivation. For the first time, we described the pRiA4-transformed callus cultures' PGR-dependent ROS status, growth, and specialized metabolism. As we have shown, expression of the rolA and rolB but not the rolC genes is contradictory in a PGR-dependent manner. Moreover, a PGR-free pRiA4 transformed cell line is characterised as more anthraquinone (AQ) productive than an untransformed cell culture. These findings pertain to actual plant biotechnology: it could be the solution to troubles in choosing the best PGR combination for the cultivation of some rare, medicinal, and woody plants; wild-type Ri-plants and tissue cultures may become freed from legal controls on genetically modified organisms in the future. We propose possible PGR-dependent relationships between rolA and rolB as well as ROS signalling targets. The present study highlighted the high importance of the rolA gene in the regulation of combined rol gene effects and the large knowledge gap in rolA action.

RevDate: 2023-08-07

Ren CY, Xu QJ, Alvarez PJJ, et al (2023)

Simultaneous antibiotic removal and mitigation of resistance induction by manganese bio-oxidation process.

Water research, 244:120442 pii:S0043-1354(23)00882-5 [Epub ahead of print].

Microbial degradation to remove residual antibiotics in wastewater is of growing interest. However, biological treatment of antibiotics may cause resistance dissemination by mutations and horizontal gene transfer (HGT) of antibiotic resistance genes (ARGs). In this study, a Mn(Ⅱ)-oxidizing bacterium (MnOB), Pseudomonas aeruginosa MQ2, simultaneously degraded antibiotics, decreased HGT, and mitigated antibiotic resistance mutation. Intracellular Mn(II) levels increased during manganese oxidation, and biogenic manganese oxides (BioMnOx, including Mn(II), Mn(III) and Mn(IV)) tightly coated the cell surface. Mn(II) bio-oxidation mitigated antibiotic resistance acquisition from an E. coli ARG donor and mitigated antibiotic resistance inducement by decreasing conjugative transfer and mutation, respectively. BioMnOx also oxidized ciprofloxacin (1 mg/L) and tetracycline (5 mg/L), respectively removing 93% and 96% within 24 h. Transcriptomic analysis revealed that two new multicopper oxidase and one peroxidase genes are involved in Mn(II) oxidation. Downregulation of SOS response, multidrug resistance and type Ⅳ secretion system related genes explained that Mn(II) and BioMnOx decreased HGT and mitigated resistance mutation by alleviating oxidative stress, which makes recipient cells more vulnerable to ARG acquisition and mutation. A manganese bio-oxidation based reactor was constructed and completely removed tetracycline with environmental concentration within 4-hour hydraulic retention time. Overall, this study suggests that Mn (II) bio-oxidation process could be exploited to control antibiotic contamination and mitigate resistance propagation during water treatment.

RevDate: 2023-08-07

Pas C, Latka A, Fieseler L, et al (2023)

Phage tailspike modularity and horizontal gene transfer reveals specificity towards E. coli O-antigen serogroups.

Virology journal, 20(1):174.

BACKGROUND: The interaction between bacteriophages and their hosts is intricate and highly specific. Receptor-binding proteins (RBPs) of phages such as tail fibers and tailspikes initiate the infection process. These RBPs bind to diverse outer membrane structures, including the O-antigen, which is a serogroup-specific sugar-based component of the outer lipopolysaccharide layer of Gram-negative bacteria. Among the most virulent Escherichia coli strains is the Shiga toxin-producing E. coli (STEC) pathotype dominated by a subset of O-antigen serogroups.

METHODS: Extensive phylogenetic and structural analyses were used to identify and validate specificity correlations between phage RBP subtypes and STEC O-antigen serogroups, relying on the principle of horizontal gene transfer as main driver for RBP evolution.

RESULTS: We identified O-antigen specific RBP subtypes for seven out of nine most prevalent STEC serogroups (O26, O45, O103, O104, O111, O145 and O157) and seven additional E. coli serogroups (O2, O8, O16, O18, 4s/O22, O77 and O78). Eight phage genera (Gamaleya-, Justusliebig-, Kaguna-, Kayfuna-, Kutter-, Lederberg-, Nouzilly- and Uetakeviruses) emerged for their high proportion of serogroup-specific RBPs. Additionally, we reveal sequence motifs in the RBP region, potentially serving as recombination hotspots between lytic phages.

CONCLUSION: The results contribute to a better understanding of mosaicism of phage RBPs, but also demonstrate a method to identify and validate new RBP subtypes for current and future emerging serogroups.

RevDate: 2023-08-07

Sahu N, Indic B, Wong-Bajracharya J, et al (2023)

Vertical and horizontal gene transfer shaped plant colonization and biomass degradation in the fungal genus Armillaria.

Nature microbiology [Epub ahead of print].

The fungal genus Armillaria contains necrotrophic pathogens and some of the largest terrestrial organisms that cause tremendous losses in diverse ecosystems, yet how they evolved pathogenicity in a clade of dominantly non-pathogenic wood degraders remains elusive. Here we show that Armillaria species, in addition to gene duplications and de novo gene origins, acquired at least 1,025 genes via 124 horizontal gene transfer events, primarily from Ascomycota. Horizontal gene transfer might have affected plant biomass degrading and virulence abilities of Armillaria, and provides an explanation for their unusual, soft rot-like wood decay strategy. Combined multi-species expression data revealed extensive regulation of horizontally acquired and wood-decay related genes, putative virulence factors and two novel conserved pathogenicity-induced small secreted proteins, which induced necrosis in planta. Overall, this study details how evolution knitted together horizontally and vertically inherited genes in complex adaptive traits of plant biomass degradation and pathogenicity in important fungal pathogens.

RevDate: 2023-08-07

Zackova Suchanova J, Bilcke G, Romanowska B, et al (2023)

Diatom adhesive trail proteins acquired by horizontal gene transfer from bacteria serve as primers for marine biofilm formation.

The New phytologist [Epub ahead of print].

Biofilm-forming benthic diatoms are key primary producers in coastal habitats, where they frequently dominate sunlit intertidal substrata. The development of gliding motility in raphid diatoms was a key molecular adaptation that contributed to their evolutionary success. However, the structure-function correlation between diatom adhesives utilized for gliding and their relationship to the extracellular matrix that constitutes the diatom biofilm is unknown. Here, we have used proteomics, immunolocalization, comparative genomics, phylogenetics and structural homology analysis to investigate the evolutionary history and function of diatom adhesive proteins. Our study identified eight proteins from the adhesive trails of Craspedostauros australis, of which four form a new protein family called Trailins that contain an enigmatic Choice-of-Anchor A (CAA) domain, which was acquired through horizontal gene transfer from bacteria. Notably, the CAA-domain shares a striking structural similarity with one of the most widespread domains found in ice-binding proteins (IPR021884). Our work offers new insights into the molecular basis for diatom biofilm formation, shedding light on the function and evolution of diatom adhesive proteins. This discovery suggests that there is a transition in the composition of biomolecules required for initial surface colonization and those utilized for 3D biofilm matrix formation.

RevDate: 2023-08-04

Nielsen TK, Winther-Have CS, Thomsen IM, et al (2023)

Genetic rearrangements in Pseudomonas amygdali pathovar aesculi shape coronatine plasmids.

Infection, genetics and evolution : journal of molecular epidemiology and evolutionary genetics in infectious diseases pii:S1567-1348(23)00084-9 [Epub ahead of print].

Plant pathogenic Pseudomonas species use multiple classes of toxins and virulence factors during host infection. The genes encoding these pathogenicity factors are often located on plasmids and other mobile genetic elements, suggesting that they are acquired through horizontal gene transfer to confer an evolutionary advantage for successful adaptation to host infection. However, the genetic rearrangements that have led to mobilization of the pathogenicity genes are not fully understood. In this study, we have sequenced and analyzed the complete genome sequences of four Pseudomonas amygdali pv. aesculi (Pae), which infect European horse chestnut trees (Aesculus hippocastanum) and belong to phylogroup 3 of the P. syringae species complex. The four investigated genomes contain six groups of plasmids that all encode pathogenicity factors. Effector genes were found to be mostly associated with insertion sequence elements, suggesting that virulence genes are generally mobilized and potentially undergo horizontal gene transfer after transfer to a conjugative plasmid. We show that the biosynthetic gene cluster encoding the phytotoxin coronatine was recently transferred from a chromosomal location to a mobilizable plasmid that subsequently formed a co-integrate with a conjugative plasmid.

RevDate: 2023-08-04

Li S, Li X, Chang H, et al (2023)

Comprehensive insights into antibiotic resistance gene migration in microalgal-bacterial consortia: Mechanisms, factors, and perspectives.

The Science of the total environment pii:S0048-9697(23)04654-5 [Epub ahead of print].

With the overuse of antibiotics, antibiotic resistance gene (ARG) prevalence is gradually increasing. ARGs are considered emerging contaminants that are broadly concentrated and dispersed in most aquatic environments. Recently, interest in microalgal-bacterial biotreatment of antibiotics has increased, as eukaryotes are not the primary target of antimicrobial drugs. Moreover, research has shown that microalgal-bacterial consortia can minimize the transmission of antibiotic resistance in the environment. Unfortunately, reviews surrounding the ARG migration mechanism in microalgal-bacterial consortia have not yet been performed. This review briefly introduces the migration of ARGs in aquatic environments. Additionally, an in-depth summary of horizontal gene transfer (HGT) between cyanobacteria and bacteria and from bacteria to eukaryotic microalgae is presented. Factors influencing gene transfer in microalgal-bacterial consortia are discussed systematically, including bacteriophage abundance, environmental conditions (temperature, pH, and nutrient availability), and other selective pressure conditions including nanomaterials, heavy metals, and pharmaceuticals and personal care products. Furthermore, considering that quorum sensing could be involved in DNA transformation by affecting secondary metabolites, current knowledge surrounding quorum sensing regulation of HGT of ARGs is summarized. In summary, this review gives valuable information to promote the development of practical and innovative techniques for ARG removal by microalgal-bacterial consortia.

RevDate: 2023-08-03

Lund D, Coertze RD, Parras-Moltó M, et al (2023)

Extensive screening reveals previously undiscovered aminoglycoside resistance genes in human pathogens.

Communications biology, 6(1):812.

Antibiotic resistance is a growing threat to human health, caused in part by pathogens accumulating antibiotic resistance genes (ARGs) through horizontal gene transfer. New ARGs are typically not recognized until they have become widely disseminated, which limits our ability to reduce their spread. In this study, we use large-scale computational screening of bacterial genomes to identify previously undiscovered mobile ARGs in pathogens. From ~1 million genomes, we predict 1,071,815 genes encoding 34,053 unique aminoglycoside-modifying enzymes (AMEs). These cluster into 7,612 families (<70% amino acid identity) of which 88 are previously described. Fifty new AME families are associated with mobile genetic elements and pathogenic hosts. From these, 24 of 28 experimentally tested AMEs confer resistance to aminoglycoside(s) in Escherichia coli, with 17 providing resistance above clinical breakpoints. This study greatly expands the range of clinically relevant aminoglycoside resistance determinants and demonstrates that computational methods enable early discovery of potentially emerging ARGs.

RevDate: 2023-08-03

Groisman EA, J Choi (2023)

Advancing evolution: Bacteria break down gene silencer to express horizontally acquired genes.

BioEssays : news and reviews in molecular, cellular and developmental biology [Epub ahead of print].

Horizontal gene transfer advances bacterial evolution. To benefit from horizontally acquired genes, enteric bacteria must overcome silencing caused when the widespread heat-stable nucleoid structuring (H-NS) protein binds to AT-rich horizontally acquired genes. This ability had previously been ascribed to both anti-silencing proteins outcompeting H-NS for binding to AT-rich DNA and RNA polymerase initiating transcription from alternative promoters. However, we now know that pathogenic Salmonella enterica serovar Typhimurium and commensal Escherichia coli break down H-NS when this silencer is not bound to DNA. Curiously, both species use the same protease - Lon - to destroy H-NS in distinct environments. Anti-silencing proteins promote the expression of horizontally acquired genes without binding to them by displacing H-NS from AT-rich DNA, thus leaving H-NS susceptible to proteolysis and decreasing H-NS amounts overall. Conserved amino acid sequences in the Lon protease and H-NS cleavage site suggest that diverse bacteria degrade H-NS to exploit horizontally acquired genes.

RevDate: 2023-08-03

Shin NR, Y Pauchet (2023)

First evidence of a horizontally-acquired GH-7 cellobiohydrolase from a longhorned beetle genome.

Archives of insect biochemistry and physiology [Epub ahead of print].

Xylophagous larvae of longhorned beetles (Coleoptera; Cerambycidae) efficiently break down polysaccharides of the plant cell wall, which make the bulk of their food, using a range of carbohydrate-active enzymes (CAZymes). In this study, we investigated the function and evolutionary history of the first identified example of insect-encoded members of glycoside hydrolase family 7 (GH7) derived from the Lamiinae Exocentrus adspersus. The genome of this beetle contained two genes encoding GH7 proteins located in tandem and flanked by transposable elements. Phylogenetic analysis revealed that the GH7 sequences of E. adspersus were closely related to those of Ascomycete fungi, suggesting that they were acquired through horizontal gene transfer (HGT) from fungi. However, they were more distantly related to those encoded by genomes of Crustacea and of protist symbionts of termites and cockroaches, supporting that the same enzyme family was recruited several times independently in Metazoa during the course of their evolution. The recombinant E. adspersus GH7 was found to primarily break down cellulose polysaccharides into cellobiose, indicating that it is a cellobiohydrolase, and could also use smaller cellulose oligomers as substrates. Additionally, the cellobiohydrolase activity was boosted by the presence of calcium chloride. Our findings suggest that the combination of GH7 cellobiohydrolases with other previously characterized endo-β-1,4-glucanases and β-glucosidases allows longhorned beetles like E. adspersus to efficiently break down cellulose into monomeric glucose.


ESP Quick Facts

ESP Origins

In the early 1990's, Robert Robbins was a faculty member at Johns Hopkins, where he directed the informatics core of GDB — the human gene-mapping database of the international human genome project. To share papers with colleagues around the world, he set up a small paper-sharing section on his personal web page. This small project evolved into The Electronic Scholarly Publishing Project.

ESP Support

In 1995, Robbins became the VP/IT of the Fred Hutchinson Cancer Research Center in Seattle, WA. Soon after arriving in Seattle, Robbins secured funding, through the ELSI component of the US Human Genome Project, to create the original ESP.ORG web site, with the formal goal of providing free, world-wide access to the literature of classical genetics.

ESP Rationale

Although the methods of molecular biology can seem almost magical to the uninitiated, the original techniques of classical genetics are readily appreciated by one and all: cross individuals that differ in some inherited trait, collect all of the progeny, score their attributes, and propose mechanisms to explain the patterns of inheritance observed.

ESP Goal

In reading the early works of classical genetics, one is drawn, almost inexorably, into ever more complex models, until molecular explanations begin to seem both necessary and natural. At that point, the tools for understanding genome research are at hand. Assisting readers reach this point was the original goal of The Electronic Scholarly Publishing Project.

ESP Usage

Usage of the site grew rapidly and has remained high. Faculty began to use the site for their assigned readings. Other on-line publishers, ranging from The New York Times to Nature referenced ESP materials in their own publications. Nobel laureates (e.g., Joshua Lederberg) regularly used the site and even wrote to suggest changes and improvements.

ESP Content

When the site began, no journals were making their early content available in digital format. As a result, ESP was obliged to digitize classic literature before it could be made available. For many important papers — such as Mendel's original paper or the first genetic map — ESP had to produce entirely new typeset versions of the works, if they were to be available in a high-quality format.

ESP Help

Early support from the DOE component of the Human Genome Project was critically important for getting the ESP project on a firm foundation. Since that funding ended (nearly 20 years ago), the project has been operated as a purely volunteer effort. Anyone wishing to assist in these efforts should send an email to Robbins.

ESP Plans

With the development of methods for adding typeset side notes to PDF files, the ESP project now plans to add annotated versions of some classical papers to its holdings. We also plan to add new reference and pedagogical material. We have already started providing regularly updated, comprehensive bibliographies to the ESP.ORG site.


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If you thought that the history of life could be organized into a simple tree and that genes only moved from parents to progeny, think again. Recent science has shown that sometimes genes move sideways, skipping the reproductive process, and the tree of life looks more like a tangled bush. David Quammen, a masterful science writer, explains these new findings and more. Read this book and you'll learn about the discovery of the archaea — an entirely different form of life, living right here on this planet, and not noticed until Carl Woese found them, by being among the first to use molecular tools to look at organismal relationships. R. Robbins

Electronic Scholarly Publishing
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Bellingham, WA 98226

E-mail: RJR8222 @

Papers in Classical Genetics

The ESP began as an effort to share a handful of key papers from the early days of classical genetics. Now the collection has grown to include hundreds of papers, in full-text format.

Digital Books

Along with papers on classical genetics, ESP offers a collection of full-text digital books, including many works by Darwin (and even a collection of poetry — Chicago Poems by Carl Sandburg).


ESP now offers a much improved and expanded collection of timelines, designed to give the user choice over subject matter and dates.


Biographical information about many key scientists.

Selected Bibliographies

Bibliographies on several topics of potential interest to the ESP community are now being automatically maintained and generated on the ESP site.

ESP Picks from Around the Web (updated 07 JUL 2018 )