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Bibliography on: Pangenome

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ESP: PubMed Auto Bibliography 08 Jul 2020 at 01:32 Created: 


Although the enforced stability of genomic content is ubiquitous among MCEs, the opposite is proving to be the case among prokaryotes, which exhibit remarkable and adaptive plasticity of genomic content. Early bacterial whole-genome sequencing efforts discovered that whenever a particular "species" was re-sequenced, new genes were found that had not been detected earlier — entirely new genes, not merely new alleles. This led to the concepts of the bacterial core-genome, the set of genes found in all members of a particular "species", and the flex-genome, the set of genes found in some, but not all members of the "species". Together these make up the species' pan-genome.

Created with PubMed® Query: pangenome or "pan-genome" or "pan genome" NOT pmcbook NOT ispreviousversion

Citations The Papers (from PubMed®)


RevDate: 2020-07-07

Shahi N, SK Mallik (2020)

Emerging bacterial fish pathogen Lactococcus garvieae RTCLI04, isolated from rainbow trout (Oncorhynchus mykiss): Genomic features and comparative genomics.

Microbial pathogenesis pii:S0882-4010(20)30734-8 [Epub ahead of print].

Lactococcus garvieae is one of the emerging zoonotic bacterial pathogen, causes fatal hemorrhagic septicemia in cultured fish species, animals and humans, worldwide. Here, we report the genomic features of whole-genome sequence (WGS) of L. garvieae strain RTCLI04, recovered from lower intestine of farmed rainbow trout, Oncorhynchus mykiss in the northwest Himalayan region India. The genome of L. garvieae RTCLI04 is a single circular chromosome of 2,054,885 base pairs (bp), which encodes 1,993 proteins and has G + C content of 39%. The bioinformatics analysis of WGS of RTCLI04, confirmed the presence of 51 tRNAs genes (including two pseudogenes), six rRNAs genes (four genes for 5S rRNA; one gene for 16S rRNA and one gene for 23S rRNA), five virulent domains, and twenty eight different genetic pathways. A Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) finder tool indicates that three different CRISPR and one cas system with common spacer was present in the genome of L. garvieae RTCLI04. Pan-genome analysis of RTCLI04 and all the other reference L. garvieae strains shows that pan-genome of this bacterium consisted of 2,239 putative protein-coding genes in which 1,850 genes are core gene, 389 genes are dispensable gene, and 221 genes are unique to RTCLI04. L. garvieae RTCLI04 lacks genomic island of 16.5 Kb capsule gene cluster. In addition, 39 virulence-associated genes (VAGs) including hly1,-2,-3; PavA, PsaA; eno; LPxTG containing surface proteins 1, 2, 3 and 4; pgm, sod and 29 antimicrobial resistant genes (ARGs) including mefE (clindamycin), srmB (lincomycin), dfrA26 (trimethoprim), gyrB (nalidixic acid), arr-3 (rifampin), otrB (tetracycline), aac(6)-Ic (tobramycin), IrgB (penicillin), mecA (oxacillin), vanRB (vancomycin) and mfpA (fluoroquinolone) were also predicted in the genome of L. garvieae RTCLI04. Our study provides new insight into understanding the virulence mechanism, antimicrobial resistance, and development of effective therapeutic measures against L. garvieae during a disease outbreak in aquaculture.

RevDate: 2020-07-07

Lyu J (2020)

Pan-genome upgrade.

Nature plants pii:10.1038/s41477-020-0731-2 [Epub ahead of print].

RevDate: 2020-07-07

Hurel J, Schbath S, Bougeard S, et al (2020)

DUGMO: tool for the detection of unknown genetically modified organisms with high-throughput sequencing data for pure bacterial samples.

BMC bioinformatics, 21(1):284 pii:10.1186/s12859-020-03611-5.

BACKGROUND: The European Community has adopted very restrictive policies regarding the dissemination and use of genetically modified organisms (GMOs). In fact, a maximum threshold of 0.9% of contaminating GMOs is tolerated for a "GMO-free" label. In recent years, imports of undescribed GMOs have been detected. Their sequences are not described and therefore not detectable by conventional approaches, such as PCR.

RESULTS: We developed DUGMO, a bioinformatics pipeline for the detection of genetically modified (GM) bacteria, including unknown GM bacteria, based on Illumina paired-end sequencing data. The method is currently focused on the detection of GM bacteria with - possibly partial - transgenes in pure bacterial samples. In the preliminary steps, coding sequences (CDSs) are aligned through two successive BLASTN against the host pangenome with relevant tuned parameters to discriminate CDSs belonging to the wild type genome (wgCDS) from potential GM coding sequences (pgmCDSs). Then, Bray-Curtis distances are calculated between the wgCDS and each pgmCDS, based on the difference of genomic vocabulary. Finally, two machine learning methods, namely the Random Forest and Generalized Linear Model, are carried out to target true GM CDS(s), based on six variables including Bray-Curtis distances and GC content. Tests carried out on a GM Bacillus subtilis showed 25 positive CDSs corresponding to the chloramphenicol resistance gene and CDSs of the inserted plasmids. On a wild type B. subtilis, no false positive sequences were detected.

CONCLUSION: DUGMO detects exogenous CDS, truncated, fused or highly mutated wild CDSs in high-throughput sequencing data, and was shown to be efficient at detecting GM sequences, but it might also be employed for the identification of recent horizontal gene transfers.

RevDate: 2020-07-03

Kaushal G, SP Singh (2020)

Comparative genome analysis provides shreds of molecular evidence for reclassification of Leuconostoc mesenteroides MTCC10508 as a strain of Leu. suionicum.

Genomics pii:S0888-7543(20)30015-X [Epub ahead of print].

This study presents the whole-genome comparative analysis of a Leuconostoc sp. strain, previously documented as Leu. mesenteroides MTCC 10508. The ANI, dDDH, dot plot, and MAUVE analyses suggested its reclassification as a strain of Leu. suionicum. Functional annotation identified a total of 1971 genes, out of which, 265 genes were mapped to CAZymes, evincing its carbohydrate transforming capability. The genome comparison with 59 Leu. mesenteroides, and Leu. suionicum strains generated the core and pan-genome profiles, divulging the unique genes in Leuconostoc sp. MTCC 10508. For the first time, this study reports the genes encoding alpha-xylosidase and copper oxidase in a strain of Leu. suionicum. The genetic information for any possible allergenic molecule could not be detected in the genome, advocating the safety of the strain. The present investigation provides the genomic evidence for reclassification of the Leuconostoc sp. strain and also promulgates the molecular insights into its metabolic potential.

RevDate: 2020-07-03

Duru IC, Andreevskaya M, Laine P, et al (2020)

Genomic characterization of the most barotolerant Listeria monocytogenes RO15 strain compared to reference strains used to evaluate food high pressure processing.

BMC genomics, 21(1):455 pii:10.1186/s12864-020-06819-0.

BACKGROUND: High pressure processing (HPP; i.e. 100-600 MPa pressure depending on product) is a non-thermal preservation technique adopted by the food industry to decrease significantly foodborne pathogens, including Listeria monocytogenes, from food. However, susceptibility towards pressure differs among diverse strains of L. monocytogenes and it is unclear if this is due to their intrinsic characteristics related to genomic content. Here, we tested the barotolerance of 10 different L. monocytogenes strains, from food and food processing environments and widely used reference strains including clinical isolate, to pressure treatments with 400 and 600 MPa. Genome sequencing and genome comparison of the tested L. monocytogenes strains were performed to investigate the relation between genomic profile and pressure tolerance.

RESULTS: None of the tested strains were tolerant to 600 MPa. A reduction of more than 5 log10 was observed for all strains after 1 min 600 MPa pressure treatment. L. monocytogenes strain RO15 showed no significant reduction in viable cell counts after 400 MPa for 1 min and was therefore defined as barotolerant. Genome analysis of so far unsequenced L. monocytogenes strain RO15, 2HF33, MB5, AB199, AB120, C7, and RO4 allowed us to compare the gene content of all strains tested. This revealed that the three most pressure tolerant strains had more than one CRISPR system with self-targeting spacers. Furthermore, several anti-CRISPR genes were detected in these strains. Pan-genome analysis showed that 10 prophage genes were significantly associated with the three most barotolerant strains.

CONCLUSIONS: L. monocytogenes strain RO15 was the most pressure tolerant among the selected strains. Genome comparison suggests that there might be a relationship between prophages and pressure tolerance in L. monocytogenes.

RevDate: 2020-07-02

Steinbrenner AD (2020)

The evolving landscape of cell surface pattern recognition across plant immune networks.

Current opinion in plant biology, 56:135-146 pii:S1369-5266(20)30053-4 [Epub ahead of print].

To recognize diverse threats, plants monitor extracellular molecular patterns and transduce intracellular immune signaling through receptor complexes at the plasma membrane. Pattern recognition occurs through a prototypical network of interacting proteins, comprising A) receptors that recognize inputs associated with a growing number of pest and pathogen classes (bacteria, fungi, oomycetes, caterpillars), B) co-receptor kinases that participate in binding and signaling, and C) cytoplasmic kinases that mediate first stages of immune output. While this framework has been elucidated in reference accessions of model organisms, network components are part of gene families with widespread variation, potentially tuning immunocompetence for specific contexts. Most dramatically, variation in receptor repertoires determines the range of ligands acting as immunogenic inputs for a given plant. Diversification of receptor kinase (RK) and related receptor-like protein (RLP) repertoires may tune responses even within a species. Comparative genomics at pangenome scale will reveal patterns and features of immune network variation.

RevDate: 2020-07-02

Chen Z, Kuang D, Xu X, et al (2020)

Genomic analyses of multidrug-resistant Salmonella Indiana, Typhimurium, and Enteritidis isolates using MinION and MiSeq sequencing technologies.

PloS one, 15(7):e0235641 pii:PONE-D-20-08707.

We sequenced 25 isolates of phenotypically multidrug-resistant Salmonella Indiana (n = 11), Typhimurium (n = 8), and Enteritidis (n = 6) using both MinION long-read [SQK-LSK109 and flow cell (R9.4.1)] and MiSeq short-read (Nextera XT and MiSeq Reagent Kit v2) sequencing technologies to determine the advantages of each approach in terms of the characteristics of genome structure, antimicrobial resistance (AMR), virulence potential, whole-genome phylogeny, and pan-genome. The MinION reads were base-called in real-time using MinKnow 3.4.8 integrated with Guppy 3.0.7. The long-read-only assembly, Illumina-only assembly, and hybrid assembly pipelines of Unicycler 0.4.8 were used to generate the MinION, MiSeq, and hybrid assemblies, respectively. The MinION assemblies were highly contiguous compared to the MiSeq assemblies but lacked accuracy, a deficiency that was mitigated by adding the MiSeq short reads through the Unicycler hybrid assembly which corrected erroneous single nucleotide polymorphisms (SNPs). The MinION assemblies provided similar predictions of AMR and virulence potential compared to the MiSeq and hybrid assemblies, although they produced more total false negatives of AMR genotypes, primarily due to failure in identifying tetracycline resistance genes in 11 of the 19 MinION assemblies of tetracycline-resistant isolates. The MinION assemblies displayed a large genetic distance from their corresponding MiSeq and hybrid assemblies on the whole-genome phylogenetic tree, indicating that the lower read accuracy of MinION sequencing caused incorrect clustering. The pan-genome of the MinION assemblies contained significantly more accessory genes and less core genes compared to the MiSeq and hybrid assemblies, suggesting that although these assemblies were more contiguous, their sequencing errors reduced accurate genome annotations. Our research demonstrates that MinION sequencing by itself provides an efficient assessment of the genome structure, antimicrobial resistance, and virulence potential of Salmonella; however, it is not sufficient for whole-genome phylogenetic and pan-genome analyses. MinION in combination with MiSeq facilitated the most accurate genomic analyses.

RevDate: 2020-07-02

Wang B, Cheng H, Qian W, et al (2020)

Comparative genome analysis and mining of secondary metabolites of Paenibacillus polymyxa.

Genes & genetic systems [Epub ahead of print].

Paenibacillus polymyxa is a well-known Gram-positive biocontrol bacterium. It has been reported that many P. polymyxa strains can inhibit bacteria, fungi and other plant pathogens. Paenibacillus polymyxa employs a variety of mechanisms to promote plant growth, so it is necessary to understand the biocontrol ability of bacteria at the genome level. In the present study, thanks to the widespread availability of Paenibacillus genome data and the development of bioinformatics tools, we were able to analyze and mine the genomes of 43 P. polymyxa strains. The strain NCTC4744 was determined not to be P. polymyxa according to digital DNA-DNA hybridization and average nucleotide identity. By analysis of the pan-genome and the core genome, we found that the pan-genome of P. polymyxa was open and that there were 3,192 core genes. In a gene cluster analysis of secondary metabolites, 797 secondary metabolite gene clusters were found, of which 343 are not similar to known clusters and are expected to reveal a large number of new secondary metabolites. We also analyzed the plant growth-promoting genes that were mined and found, surpisingly, that these genes are highly conserved. The results of the present study not only reveal a large number of unknown potential secondary metabolite gene clusters in P. polymyxa, but also suggest that plant growth promotion characteristics are evolutionary adaptations of P. polymyxa to plant-related habitats.

RevDate: 2020-07-02

Fodor A, Abate BA, Deák P, et al (2020)

Multidrug Resistance (MDR) and Collateral Sensitivity in Bacteria, with Special Attention to Genetic and Evolutionary Aspects and to the Perspectives of Antimicrobial Peptides-A Review.

Pathogens (Basel, Switzerland), 9(7): pii:pathogens9070522.

Antibiotic poly-resistance (multidrug-, extreme-, and pan-drug resistance) is controlled by adaptive evolution. Darwinian and Lamarckian interpretations of resistance evolution are discussed. Arguments for, and against, pessimistic forecasts on a fatal "post-antibiotic era" are evaluated. In commensal niches, the appearance of a new antibiotic resistance often reduces fitness, but compensatory mutations may counteract this tendency. The appearance of new antibiotic resistance is frequently accompanied by a collateral sensitivity to other resistances. Organisms with an expanding open pan-genome, such as Acinetobacterbaumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae, can withstand an increased number of resistances by exploiting their evolutionary plasticity and disseminating clonally or poly-clonally. Multidrug-resistant pathogen clones can become predominant under antibiotic stress conditions but, under the influence of negative frequency-dependent selection, are prevented from rising to dominance in a population in a commensal niche. Antimicrobial peptides have a great potential to combat multidrug resistance, since antibiotic-resistant bacteria have shown a high frequency of collateral sensitivity to antimicrobial peptides. In addition, the mobility patterns of antibiotic resistance, and antimicrobial peptide resistance, genes are completely different. The integron trade in commensal niches is fortunately limited by the species-specificity of resistance genes. Hence, we theorize that the suggested post-antibiotic era has not yet come, and indeed might never come.

RevDate: 2020-07-01

Roder T, Wüthrich D, Bär C, et al (2020)

In Silico Comparison Shows that the Pan-Genome of a Dairy-Related Bacterial Culture Collection Covers Most Reactions Annotated to Human Microbiomes.

Microorganisms, 8(7): pii:microorganisms8070966.

The diversity of the human microbiome is positively associated with human health. However, this diversity is endangered by Westernized dietary patterns that are characterized by a decreased nutrient variety. Diversity might potentially be improved by promoting dietary patterns rich in microbial strains. Various collections of bacterial cultures resulting from a century of dairy research are readily available worldwide, and could be exploited to contribute towards this end. We have conducted a functional in silico analysis of the metagenome of 24 strains, each representing one of the species in a bacterial culture collection composed of 626 sequenced strains, and compared the pathways potentially covered by this metagenome to the intestinal metagenome of four healthy, although overweight, humans. Remarkably, the pan-genome of the 24 strains covers 89% of the human gut microbiome's annotated enzymatic reactions. Furthermore, the dairy microbial collection covers biological pathways, such as methylglyoxal degradation, sulfate reduction, g-aminobutyric (GABA) acid degradation and salicylate degradation, which are differently covered among the four subjects and are involved in a range of cardiometabolic, intestinal, and neurological disorders. We conclude that microbial culture collections derived from dairy research have the genomic potential to complement and restore functional redundancy in human microbiomes.

RevDate: 2020-06-30

Motyka-Pomagruk A, Zoledowska S, Misztak AE, et al (2020)

Comparative genomics and pangenome-oriented studies reveal high homogeneity of the agronomically relevant enterobacterial plant pathogen Dickeya solani.

BMC genomics, 21(1):449 pii:10.1186/s12864-020-06863-w.

BACKGROUND: Dickeya solani is an important plant pathogenic bacterium causing severe losses in European potato production. This species draws a lot of attention due to its remarkable virulence, great devastating potential and easier spread in contrast to other Dickeya spp. In view of a high need for extensive studies on economically important soft rot Pectobacteriaceae, we performed a comparative genomics analysis on D. solani strains to search for genetic foundations that would explain the differences in the observed virulence levels within the D. solani population.

RESULTS: High quality assemblies of 8 de novo sequenced D. solani genomes have been obtained. Whole-sequence comparison, ANIb, ANIm, Tetra and pangenome-oriented analyses performed on these genomes and the sequences of 14 additional strains revealed an exceptionally high level of homogeneity among the studied genetic material of D. solani strains. With the use of 22 genomes, the pangenome of D. solani, comprising 84.7% core, 7.2% accessory and 8.1% unique genes, has been almost completely determined, suggesting the presence of a nearly closed pangenome structure. Attribution of the genes included in the D. solani pangenome fractions to functional COG categories showed that higher percentages of accessory and unique pangenome parts in contrast to the core section are encountered in phage/mobile elements- and transcription- associated groups with the genome of RNS 05.1.2A strain having the most significant impact. Also, the first D. solani large-scale genome-wide phylogeny computed on concatenated core gene alignments is herein reported.

CONCLUSIONS: The almost closed status of D. solani pangenome achieved in this work points to the fact that the unique gene pool of this species should no longer expand. Such a feature is characteristic of taxa whose representatives either occupy isolated ecological niches or lack efficient mechanisms for gene exchange and recombination, which seems rational concerning a strictly pathogenic species with clonal population structure. Finally, no obvious correlations between the geographical origin of D. solani strains and their phylogeny were found, which might reflect the specificity of the international seed potato market.

RevDate: 2020-06-30

Yang F, Feng H, Massey IY, et al (2020)

Genome-Wide Analysis Reveals Genetic Potential for Aromatic Compounds Biodegradation of Sphingopyxis.

BioMed research international, 2020:5849123.

Members of genus Sphingopyxis are frequently found in diverse eco-environments worldwide and have been traditionally considered to play vital roles in the degradation of aromatic compounds. Over recent decades, many aromatic-degrading Sphingopyxis strains have been isolated and recorded, but little is known about their genetic nature related to aromatic compounds biodegradation. In this study, bacterial genomes of 19 Sphingopyxis strains were used for comparative analyses. Phylogeny showed an ambiguous relatedness between bacterial strains and their habitat specificity, while clustering based on Cluster of Orthologous Groups suggested the potential link of functional profile with substrate-specific traits. Pan-genome analysis revealed that 19 individuals were predicted to share 1,066 orthologous genes, indicating a high genetic homogeneity among Sphingopyxis strains. Notably, KEGG Automatic Annotation Server results suggested that most genes pertaining aromatic compounds biodegradation were predicted to be involved in benzoate, phenylalanine, and aminobenzoate metabolism. Among them, β-ketoadipate biodegradation might be the main pathway in Sphingopyxis strains. Further inspection showed that a number of mobile genetic elements varied in Sphingopyxis genomes, and plasmid-mediated gene transfer coupled with prophage- and transposon-mediated rearrangements might play prominent roles in the evolution of bacterial genomes. Collectively, our findings presented that Sphingopyxis isolates might be the promising candidates for biodegradation of aromatic compounds in pollution sites.

RevDate: 2020-06-30

Sun Z, Zhou D, Zhang X, et al (2020)

Determining the Genetic Characteristics of Resistance and Virulence of the "Epidermidis Cluster Group" Through Pan-Genome Analysis.

Frontiers in cellular and infection microbiology, 10:274.

Staphylococcus caprae, Staphylococcus capitis, and Staphylococcus epidermidis belong to the "Epidermidis Cluster Group" (ECG) and are generally opportunistic pathogens. In this work, whole genome sequencing, molecular cloning and pan-genome analysis were performed to investigate the genetic characteristics of the resistance, virulence and genome structures of 69 ECG strains, including a clinical isolate (S. caprae SY333) obtained in this work. Two resistance genes (blaZ and aadD2) encoded on the plasmids pSY333-41 and pSY333-45 of S. caprae SY333 were confirmed to be functional. The bla region in ECG exhibited three distinct structures, and these chromosome- and plasmid-encoded bla operons seemed to follow two different evolutionary paths. Pan-genome analysis revealed their pan-genomes tend to be "open." For the virulence-related factors, the genes involved in primary attachment were observed almost exclusively in S. epidermidis, while the genes associated with intercellular aggregation were observed more frequently in S. caprae and S. capitis. The type VII secretion system was present in all strains of S. caprae and some of S. epidermidis but not in S. capitis. Moreover, the isd locus (iron regulated surface determinant) was first found to be encoded on the genomes of S. caprae and S. capitis. These findings suggested that the plasmid and chromosome encoded bla operons of ECG species underwent different evolution paths, as well as they differed in the abundance of virulence genes associated with adherence, invasion, secretion system and immune evasion. Identification of isd loci in S. caprae and S. capitis indicated their ability to acquire heme as nutrient iron during infection.

RevDate: 2020-06-26

Nishitsuji K, Arimoto A, Yonashiro Y, et al (2020)

Comparative genomics of four strains of the edible brown alga, Cladosiphon okamuranus.

BMC genomics, 21(1):422 pii:10.1186/s12864-020-06792-8.

BACKGROUND: The brown alga, Cladosiphon okamuranus (Okinawa mozuku), is one of the most important edible seaweeds, and it is cultivated for market primarily in Okinawa, Japan. Four strains, denominated S, K, O, and C, with distinctively different morphologies, have been cultivated commercially since the early 2000s. We previously reported a draft genome of the S-strain. To facilitate studies of seaweed biology for future aquaculture, we here decoded and analyzed genomes of the other three strains (K, O, and C).

RESULTS: Here we improved the genome of the S-strain (ver. 2, 130 Mbp, 12,999 genes), and decoded the K-strain (135 Mbp, 12,511 genes), the O-strain (140 Mbp, 12,548 genes), and the C-strain (143 Mbp, 12,182 genes). Molecular phylogenies, using mitochondrial and nuclear genes, showed that the S-strain diverged first, followed by the K-strain, and most recently the C- and O-strains. Comparisons of genome architecture among the four strains document the frequent occurrence of inversions. In addition to gene acquisitions and losses, the S-, K-, O-, and C-strains possess 457, 344, 367, and 262 gene families unique to each strain, respectively. Comprehensive Blast searches showed that most genes have no sequence similarity to any entries in the non-redundant protein sequence database, although GO annotation suggested that they likely function in relation to molecular and biological processes and cellular components.

CONCLUSIONS: Our study compares the genomes of four strains of C. okamuranus and examines their phylogenetic relationships. Due to global environmental changes, including temperature increases, acidification, and pollution, brown algal aquaculture is facing critical challenges. Genomic and phylogenetic information reported by the present research provides useful tools for isolation of novel strains.

RevDate: 2020-06-25

Collis RM, Biggs PJ, Midwinter AC, et al (2020)

Genomic epidemiology and carbon metabolism of Escherichia coli serogroup O145 reflect contrasting phylogenies.

PloS one, 15(6):e0235066 pii:PONE-D-20-02830.

Shiga toxin-producing Escherichia coli (STEC) are a leading cause of foodborne outbreaks of human disease, but they reside harmlessly as an asymptomatic commensal in the ruminant gut. STEC serogroup O145 are difficult to isolate as routine diagnostic methods are unable to distinguish non-O157 serogroups due to their heterogeneous metabolic characteristics, resulting in under-reporting which is likely to conceal their true prevalence. In light of these deficiencies, the purpose of this study was a twofold approach to investigate enhanced STEC O145 diagnostic culture-based methods: firstly, to use a genomic epidemiology approach to understand the genetic diversity and population structure of serogroup O145 at both a local (New Zealand) (n = 47) and global scale (n = 75) and, secondly, to identify metabolic characteristics that will help the development of a differential media for this serogroup. Analysis of a subset of E. coli serogroup O145 strains demonstrated considerable diversity in carbon utilisation, which varied in association with eae subtype and sequence type. Several carbon substrates, such as D-serine and D-malic acid, were utilised by the majority of serogroup O145 strains, which, when coupled with current molecular and culture-based methods, could aid in the identification of presumptive E. coli serogroup O145 isolates. These carbon substrates warrant subsequent testing with additional serogroup O145 strains and non-O145 strains. Serogroup O145 strains displayed extensive genetic heterogeneity that was correlated with sequence type and eae subtype, suggesting these genetic markers are good indicators for distinct E. coli phylogenetic lineages. Pangenome analysis identified a core of 3,036 genes and an open pangenome of >14,000 genes, which is consistent with the identification of distinct phylogenetic lineages. Overall, this study highlighted the phenotypic and genotypic heterogeneity within E. coli serogroup O145, suggesting that the development of a differential media targeting this serogroup will be challenging.

RevDate: 2020-06-23

Vázquez-Rosas-Landa M, Ponce-Soto GY, Aguirre-Liguori JA, et al (2020)

Population genomics of Vibrionaceae isolated from an endangered oasis reveals local adaptation after an environmental perturbation.

BMC genomics, 21(1):418 pii:10.1186/s12864-020-06829-y.

BACKGROUND: In bacteria, pan-genomes are the result of an evolutionary "tug of war" between selection and horizontal gene transfer (HGT). High rates of HGT increase the genetic pool and the effective population size (Ne), resulting in open pan-genomes. In contrast, selective pressures can lead to local adaptation by purging the variation introduced by HGT and mutation, resulting in closed pan-genomes and clonal lineages. In this study, we explored both hypotheses, elucidating the pan-genome of Vibrionaceae isolates after a perturbation event in the endangered oasis of Cuatro Ciénegas Basin (CCB), Mexico, and looking for signals of adaptation to the environments in their genomes.

RESULTS: We obtained 42 genomes of Vibrionaceae distributed in six lineages, two of them did not showed any close reference strain in databases. Five of the lineages showed closed pan-genomes and were associated to either water or sediment environment; their high Ne estimates suggest that these lineages are not from a recent origin. The only clade with an open pan-genome was found in both environments and was formed by ten genetic groups with low Ne, suggesting a recent origin. The recombination and mutation estimators (r/m) ranged from 0.005 to 2.725, which are similar to oceanic Vibrionaceae estimations. However, we identified 367 gene families with signals of positive selection, most of them found in the core genome; suggesting that despite recombination, natural selection moves the Vibrionaceae CCB lineages to local adaptation, purging the genomes and keeping closed pan-genome patterns. Moreover, we identify 598 SNPs associated with an unstructured environment; some of the genes associated with these SNPs were related to sodium transport.

CONCLUSIONS: Different lines of evidence suggest that the sampled Vibrionaceae, are part of the rare biosphere usually living under famine conditions. Two of these lineages were reported for the first time. Most Vibrionaceae lineages of CCB are adapted to their micro-habitats rather than to the sampled environments. This pattern of adaptation is concordant with the association of closed pan-genomes and local adaptation.

RevDate: 2020-06-20

Anani H, Zgheib R, Hasni I, et al (2020)

Interest of bacterial pangenome analyses in clinical microbiology.

Microbial pathogenesis pii:S0882-4010(20)30641-0 [Epub ahead of print].

Thanks to the progress and decreasing costs in genome sequencing technologies, more than 250,000 bacterial genomes are currently available in public databases, covering most, if not all, of the major human-associated phylogenetic groups of these microorganisms, pathogenic or not. In addition, for many of them, sequences from several strains of a given species are available, thus enabling to evaluate their genetic diversity and study their evolution. In addition, the significant cost reduction of bacterial whole genome sequencing as well as the rapid increase in the number of available bacterial genomes have prompted the development of pangenomic software tools. The study of bacterial pangenome has many applications in clinical microbiology. It can unveil the pathogenic potential and ability of bacteria to resist antimicrobials as well identify specific sequences and predict antigenic epitopes that allow molecular or serologic assays and vaccines to be designed. Bacterial pangenome constitutes a powerful method for understanding the history of human bacteria and relating these findings to diagnosis in clinical microbiology laboratories in order to optimize patient management.

RevDate: 2020-06-19

Liu Y, Du H, Li P, et al (2020)

Pan-Genome of Wild and Cultivated Soybeans.

Cell pii:S0092-8674(20)30618-8 [Epub ahead of print].

Soybean is one of the most important vegetable oil and protein feed crops. To capture the entire genomic diversity, it is needed to construct a complete high-quality pan-genome from diverse soybean accessions. In this study, we performed individual de novo genome assemblies for 26 representative soybeans that were selected from 2,898 deeply sequenced accessions. Using these assembled genomes together with three previously reported genomes, we constructed a graph-based genome and performed pan-genome analysis, which identified numerous genetic variations that cannot be detected by direct mapping of short sequence reads onto a single reference genome. The structural variations from the 2,898 accessions that were genotyped based on the graph-based genome and the RNA sequencing (RNA-seq) data from the representative 26 accessions helped to link genetic variations to candidate genes that are responsible for important traits. This pan-genome resource will promote evolutionary and functional genomics studies in soybean.

RevDate: 2020-06-12

Ellegaard KM, Suenami S, Miyazaki R, et al (2020)

Vast Differences in Strain-Level Diversity in the Gut Microbiota of Two Closely Related Honey Bee Species.

Current biology : CB pii:S0960-9822(20)30586-8 [Epub ahead of print].

Most bacterial species encompass strains with vastly different gene content. Strain diversity in microbial communities is therefore considered to be of functional importance. Yet little is known about the extent to which related microbial communities differ in diversity at this level and which underlying mechanisms may constrain and maintain strain-level diversity. Here, we used shotgun metagenomics to characterize and compare the gut microbiota of two honey bee species, Apis mellifera and Apis cerana, which diverged about 6 mya. Although the host species are colonized largely by the same bacterial 16S rRNA phylotypes, we find that their communities are host specific when analyzed with genomic resolution. Moreover, despite their similar ecology, A. mellifera displayed a much higher diversity of strains and functional gene content in the microbiota compared to A. cerana, both per colony and per individual bee. In particular, the gene repertoire for polysaccharide degradation was massively expanded in the microbiota of A. mellifera relative to A. cerana. Bee management practices, divergent ecological adaptation, or habitat size may have contributed to the observed differences in microbiota genomic diversity of these key pollinator species. Our results illustrate that the gut microbiota of closely related animal hosts can differ vastly in genomic diversity while displaying similar levels of diversity based on the 16S rRNA gene. Such differences are likely to have consequences for gut microbiota functioning and host-symbiont interactions, highlighting the need for metagenomic studies to understand the ecology and evolution of microbial communities.

RevDate: 2020-06-11

Crouse A, Schramm C, Emond-Rheault JG, et al (2020)

Combining Whole-Genome Sequencing and Multimodel Phenotyping To Identify Genetic Predictors of Salmonella Virulence.

mSphere, 5(3): pii:5/3/e00293-20.

Salmonella comprises more than 2,600 serovars. Very few environmental and uncommon serovars have been characterized for their potential role in virulence and human infections. A complementary in vitro and in vivo systematic high-throughput analysis of virulence was used to elucidate the association between genetic and phenotypic variations across Salmonella isolates. The goal was to develop a strategy for the classification of isolates as a benchmark and predict virulence levels of isolates. Thirty-five phylogenetically distant strains of unknown virulence were selected from the Salmonella Foodborne Syst-OMICS (SalFoS) collection, representing 34 different serovars isolated from various sources. Isolates were evaluated for virulence in 4 complementary models of infection to compare virulence traits with the genomics data, including interactions with human intestinal epithelial cells, human macrophages, and amoeba. In vivo testing was conducted using the mouse model of Salmonella systemic infection. Significant correlations were identified between the different models. We identified a collection of novel hypothetical and conserved proteins associated with isolates that generate a high burden. We also showed that blind prediction of virulence of 33 additional strains based on the pan-genome was high in the mouse model of systemic infection (82% agreement) and in the human epithelial cell model (74% agreement). These complementary approaches enabled us to define virulence potential in different isolates and present a novel strategy for risk assessment of specific strains and for better monitoring and source tracking during outbreaks.IMPORTANCESalmonella species are bacteria that are a major source of foodborne disease through contamination of a diversity of foods, including meat, eggs, fruits, nuts, and vegetables. More than 2,600 different Salmonella enterica serovars have been identified, and only a few of them are associated with illness in humans. Despite the fact that they are genetically closely related, there is enormous variation in the virulence of different isolates of Salmonella enterica Identification of foodborne pathogens is a lengthy process based on microbiological, biochemical, and immunological methods. Here, we worked toward new ways of integrating whole-genome sequencing (WGS) approaches into food safety practices. We used WGS to build associations between virulence and genetic diversity within 83 Salmonella isolates representing 77 different Salmonella serovars. Our work demonstrates the potential of combining a genomics approach and virulence tests to improve the diagnostics and assess risk of human illness associated with specific Salmonella isolates.

RevDate: 2020-06-10

Gori A, Harrison OB, Mlia E, et al (2020)

Pan-GWAS of Streptococcus agalactiae Highlights Lineage-Specific Genes Associated with Virulence and Niche Adaptation.

mBio, 11(3): pii:mBio.00728-20.

Streptococcus agalactiae (group B streptococcus; GBS) is a colonizer of the gastrointestinal and urogenital tracts, and an opportunistic pathogen of infants and adults. The worldwide population of GBS is characterized by clonal complexes (CCs) with different invasive potentials. CC17, for example, is a hypervirulent lineage commonly associated with neonatal sepsis and meningitis, while CC1 is less invasive in neonates and more commonly causes invasive disease in adults with comorbidities. The genetic basis of GBS virulence and the extent to which different CCs have adapted to different host environments remain uncertain. We have therefore applied a pan-genome-wide association study (GWAS) approach to 1,988 GBS strains isolated from different hosts and countries. Our analysis identified 279 CC-specific genes associated with virulence, disease, metabolism, and regulation of cellular mechanisms that may explain the differential virulence potential of particular CCs. In CC17 and CC23, for example, we have identified genes encoding pilus, quorum-sensing proteins, and proteins for the uptake of ions and micronutrients which are absent in less invasive lineages. Moreover, in CC17, carriage and disease strains were distinguished by the allelic variants of 21 of these CC-specific genes. Together our data highlight the lineage-specific basis of GBS niche adaptation and virulence.IMPORTANCE GBS is a leading cause of mortality in newborn babies in high- and low-income countries worldwide. Different strains of GBS are characterized by different degrees of virulence, where some are harmlessly carried by humans or animals and others are much more likely to cause disease.The genome sequences of almost 2,000 GBS samples isolated from both animals and humans in high- and low- income countries were analyzed using a pan-genome-wide association study approach. This allowed us to identify 279 genes which are associated with different lineages of GBS, characterized by a different virulence and preferred host. Additionally, we propose that the GBS now carried in humans may have first evolved in animals before expanding clonally once adapted to the human host.These findings are essential to help understand what is causing GBS disease and how the bacteria have evolved and are transmitted.

RevDate: 2020-06-08

Gonzales-Siles L, Karlsson R, Schmidt P, et al (2020)

A Pangenome Approach for Discerning Species-Unique Gene Markers for Identifications of Streptococcus pneumoniae and Streptococcus pseudopneumoniae.

Frontiers in cellular and infection microbiology, 10:222.

Correct identifications of isolates and strains of the Mitis-Group of the genus Streptococcus are particularly difficult, due to high genetic similarity, resulting from horizontal gene transfer and homologous recombination, and unreliable phenotypic and genotypic biomarkers for differentiating the species. Streptococcus pneumoniae and Streptococcus pseudopneumoniae are the most closely related species of the clade. In this study, publicly-available genome sequences for Streptococcus pneumoniae and S. pseudopneumoniae were analyzed, using a pangenomic approach, to find candidates for species-unique gene markers; ten species-unique genes for S. pneumoniae and nine for S. pseudopneumoniae were identified. These species-unique gene marker candidates were verified by PCR assays for identifying S. pneumoniae and S. pseudopneumoniae strains isolated from clinical samples. All determined species-level unique gene markers for S. pneumoniae were detected in all S. pneumoniae clinical isolates, whereas fewer of the unique S. pseudopneumoniae gene markers were present in more than 95% of the clinical isolates. In parallel, taxonomic identifications of the clinical isolates were confirmed, using conventional optochin sensitivity testing, targeted PCR-detection for the "Xisco" gene, as well as genomic ANIb similarity analyses for the genome sequences of selected strains. Using mass spectrometry-proteomics, species-specific peptide matches were observed for four of the S. pneumoniae gene markers and for three of the S. pseudopneumoniae gene markers. Application of multiple species-level unique biomarkers of S. pneumoniae and S. pseudopneumoniae, is proposed as a protocol for the routine clinical laboratory for improved, reliable differentiation, and identification of these pathogenic and commensal species.

RevDate: 2020-06-08

Nasr Azadani D, Zhang D, Hatherill JR, et al (2020)

Isolation, characterization, and comparative genomic analysis of a phage infecting high-level aminoglycoside-resistant (HLAR) Enterococcus faecalis.

PeerJ, 8:e9171 pii:9171.

Enterococcus is a genus of Gram-positive bacteria that are commensal to the gastrointestinal tracts of humans but some species have been increasingly implicated as agents of nosocomial infections. The increase in infections and the spread of antibiotic-resistant strains have contributed to renewed interest in the discovery of Enterococcus phages. The aims of this study were (1) the isolation, characterization, and genome sequencing of a phage capable of infecting an antibiotic-resistant E. faecalis strain, and (2) the comparative genomic analysis of publicly-available Enterococcus phages. For this purpose, multiple phages were isolated from wastewater treatment plant (WWTP) influent using a high-level aminoglycoside-resistant (HLAR) E. faecalis strain as the host. One phage, phiNASRA1, demonstrated a high lytic efficiency (∼97.52%). Transmission electron microscopy (TEM) and whole-genome sequencing (WGS) showed that phiNASRA1 belongs to the Siphoviridae family of double-stranded DNA viruses. The phage was approximately 250 nm in length and its complete genome (40,139 bp, 34.7% GC) contained 62 open reading frames (ORFs). Phylogenetic comparisons of phiNASRA1 and 31 publicly-available Enterococcus phages, based on the large subunit terminase and portal proteins, grouped phage by provenance, size, and GC content. In particular, both phylogenies grouped phages larger than 100 kbp into distinct clades. A phylogeny based on a pangenome analysis of the same 32 phages also grouped phages by provenance, size, and GC content although agreement between the two single-locus phylogenies was higher. Per the pangenome phylogeny, phiNASRA1 was most closely related to phage LY0322 that was similar in size, GC content, and number of ORFs (40,139 and 40,934 bp, 34.77 and 34.80%, and 60 and 64 ORFs, respectively). The pangenome analysis did illustrate the high degree of sequence diversity and genome plasticity as no coding sequence was homologous across all 32 phages, and even 'conserved' structural proteins (e.g., the large subunit terminase and portal proteins) were homologous in no more than half of the 32 phage genomes. These findings contribute to a growing body of literature devoted to understanding phage biology and diversity. We propose that this high degree of diversity limited the value of the single-locus and pangenome phylogenies. By contrast, the high degree of homology between phages larger than 100 kbp suggests that pangenome analyses of more similar phages is a viable method for assessing subclade diversity. Future work is focused on validating phiNASRA1 as a potential therapeutic agent to eradicate antibiotic-resistant E. faecalis infections in an animal model.

RevDate: 2020-06-04

Wang LYR, Jokinen CC, Laing CR, et al (2020)

Assessing the genomic relatedness and evolutionary rates of persistent verotoxigenic Escherichia coli serotypes within a closed beef herd in Canada.

Microbial genomics [Epub ahead of print].

Verotoxigenic Escherichia coli (VTEC) are food- and water-borne pathogens associated with both sporadic illness and outbreaks of enteric disease. While it is known that cattle are reservoirs of VTEC, little is known about the genomic variation of VTEC in cattle, and whether the variation in genomes reported for human outbreak strains is consistent with individual animal or group/herd sources of infection. A previous study of VTEC prevalence identified serotypes carried persistently by three consecutive cohorts of heifers within a closed herd of cattle. This present study aimed to: (i) determine whether the genomic relatedness of bovine isolates is similar to that reported for human strains associated with single source outbreaks, (ii) estimate the rates of genome change among dominant serotypes over time within a cattle herd, and (iii) identify genomic features of serotypes associated with persistence in cattle. Illumina MiSeq genome sequencing and genotyping based on allelic and single nucleotide variations were completed, while genome change over time was measured using Bayesian evolutionary analysis sampling trees. The accessory genome, including the non-protein-encoding intergenic regions (IGRs), virulence factors, antimicrobial-resistance genes and plasmid gene content of representative persistent and sporadic cattle strains were compared using Fisher's exact test corrected for multiple comparisons. Herd strains from serotypes O6:H34 (n=22), O22:H8 (n=30), O108:H8 (n=39), O139:H19 (n=44) and O157:H7 (n=106) were readily distinguishable from epidemiologically unrelated strains of the same serotype using a similarity threshold of 10 or fewer allele differences between adjacent nodes. Temporal-cohort clustering within each serotype was supported by date randomization analysis. Substitutions per site per year were consistent with previously reported values for E. coli; however, there was low branch support for these values. Acquisition of the phage-encoded Shiga toxin 2 gene in serotype O22:H8 was observed. Pan-genome analyses identified accessory regions that were more prevalent in persistent serotypes (P≤0.05) than in sporadic serotypes. These results suggest that VTEC serotypes from a specific cattle population are highly clonal with a similar level of relatedness as human single-source outbreak-associated strains, but changes in the genome occur gradually over time. Additionally, elements in the accessory genomes may provide a selective advantage for persistence of VTEC within cattle herds.

RevDate: 2020-06-04

Fan X, Qiu H, Han W, et al (2020)

Phytoplankton pangenome reveals extensive prokaryotic horizontal gene transfer of diverse functions.

Science advances, 6(18):eaba0111 pii:aba0111.

The extent and role of horizontal gene transfer (HGT) in phytoplankton and, more broadly, eukaryotic evolution remain controversial topics. Recent studies substantiate the importance of HGT in modifying or expanding functions such as metal or reactive species detoxification and buttressing halotolerance. Yet, the potential of HGT to significantly alter the fate of species in a major eukaryotic assemblage remains to be established. We provide such an example for the ecologically important lineages encompassed by cryptophytes, rhizarians, alveolates, stramenopiles, and haptophytes ("CRASH" taxa). We describe robust evidence of prokaryotic HGTs in these taxa affecting functions such as polysaccharide biosynthesis. Numbers of HGTs range from 0.16 to 1.44% of CRASH species gene inventories, comparable to the ca. 1% prokaryote-derived HGTs found in the genomes of extremophilic red algae. Our results substantially expand the impact of HGT in eukaryotes and define a set of general principles for prokaryotic gene fixation in phytoplankton genomes.

RevDate: 2020-06-04

Wesevich A, Sutton G, Ruffin F, et al (2020)

Newly-named Klebsiella aerogenes (formerly Enterobacter aerogenes) is Associated with Poor Clinical Outcomes Relative to other Enterobacter Species in Patients with Bloodstream Infection.

Journal of clinical microbiology pii:JCM.00582-20 [Epub ahead of print].

Objectives:Enterobacter aerogenes was recently renamed Klebsiella aerogenes This study aimed to identify differences in clinical characteristics, outcomes, and bacterial genetics among patients with K. aerogenes versus Enterobacter species bloodstream infections (BSI).Methods: We prospectively enrolled patients with K. aerogenes or Enterobacter cloacae complex (Ecc) BSI from 2002-2015. We performed whole genome sequencing (WGS) and pan-genome analysis on all bacteria.Results: Overall, 150 patients with K. aerogenes (46/150 [31%]) or Ecc (104/150 [69%]) BSI were enrolled. The two groups had similar baseline characteristics. Neither total in-hospital mortality (13/46 [28%] versus 22/104 [21%]; p=0.3) nor attributable in-hospital mortality (9/46 [20%] versus 13/104 [12%]; p=0.3) differed between patients with K. aerogenes versus Ecc BSI, respectively. However, poor clinical outcome (death before discharge, recurrent BSI, and/or BSI complication) was higher for K. aerogenes than Ecc BSI (32/46 [70%] versus 42/104 [40%]; p=0.001). In a multivariable regression model, K. aerogenes BSI, relative to Ecc BSI, was predictive of poor clinical outcome (odds ratio 3.3; 95% confidence interval 1.4-8.1; p=0.008). Pan-genome analysis revealed 983 genes in 323 genomic islands unique to K. aerogenes isolates, including putative virulence genes involved in iron acquisition (n=67), fimbriae/pili/flagella production (n=117), and metal homeostasis (n=34). Antibiotic resistance was largely found in Ecc lineage 1, which had a higher rate of multidrug resistant phenotype (23/54 [43%]) relative to all other bacterial isolates (23/96 [24%]; p=0.03).Conclusions:K. aerogenes BSI was associated with poor clinical outcomes relative to Ecc BSI. Putative virulence factors in K. aerogenes may account for these differences.

RevDate: 2020-06-01

Badet T, D Croll (2020)

The rise and fall of genes: origins and functions of plant pathogen pangenomes.

Current opinion in plant biology, 56:65-73 pii:S1369-5266(20)30049-2 [Epub ahead of print].

Plant pathogens can rapidly overcome resistance of their hosts by mutating key pathogenicity genes encoding for effectors. Pathogen adaptation is fuelled by extensive genetic variability in populations and different strains may not share the same set of genes. Recently, such an intra-specific variation in gene content became formalized as pangenomes distinguishing core genes (i.e. shared) and accessory genes (i.e. lineage or strain-specific). Across pathogens species, key effectors tend to be part of the rapidly evolving accessory genome. Here, we show how the construction and analysis of pathogen pangenomes provide deep insights into the dynamic host adaptation process. We also discuss how pangenomes should ideally be built and how geography, niche and lifestyle likely determine pangenome sizes.

RevDate: 2020-05-30

Pilar AVC, Petronella N, Dussault FM, et al (2020)

Similar yet different: phylogenomic analysis to delineate Salmonella and Citrobacter species boundaries.

BMC genomics, 21(1):377 pii:10.1186/s12864-020-06780-y.

BACKGROUND: Salmonella enterica is a leading cause of foodborne illness worldwide resulting in considerable public health and economic costs. Testing for the presence of this pathogen in food is often hampered by the presence of background microflora that may present as Salmonella (false positives). False positive isolates belonging to the genus Citrobacter can be difficult to distinguish from Salmonella due to similarities in their genetics, cell surface antigens, and other phenotypes. In order to understand the genetic basis of these similarities, a comparative genomic approach was used to define the pan-, core, accessory, and unique coding sequences of a representative population of Salmonella and Citrobacter strains.

RESULTS: Analysis of the genomic content of 58 S. enterica strains and 37 Citrobacter strains revealed the presence of 31,130 and 1540 coding sequences within the pan- and core genome of this population. Amino acid sequences unique to either Salmonella (n = 1112) or Citrobacter (n = 195) were identified and revealed potential niche-specific adaptations. Phylogenetic network analysis of the protein families encoded by the pan-genome indicated that genetic exchange between Salmonella and Citrobacter may have led to the acquisition of similar traits and also diversification within the genera.

CONCLUSIONS: Core genome analysis suggests that the Salmonella enterica and Citrobacter populations investigated here share a common evolutionary history. Comparative analysis of the core and pan-genomes was able to define the genetic features that distinguish Salmonella from Citrobacter and highlight niche specific adaptations.

RevDate: 2020-05-29

Li M, Aye SM, Ahmed MU, et al (2020)

Pan-transcriptomic analysis identified common differentially expressed genes of Acinetobacter baumannii in response to polymyxin treatments.

Molecular omics [Epub ahead of print].

Multidrug-resistant Acinetobacter baumannii is a top-priority Gram-negative pathogen and polymyxins are a last-line therapeutic option. Previous systems pharmacological studies examining polymyxin killing and resistance usually focused on individual strains, and the derived knowledge could be limited by strain-specific genomic context. In this study, we examined the gene expression of five A. baumannii strains (34654, 1207552, 1428368, 1457504 and ATCC 19606) to determine the common differentially expressed genes in response to polymyxin treatments. A pan-genome containing 6061 genes was identified for 89 A. baumannii genomes from RefSeq database which included the five strains examined in this study; 2822 of the 6061 genes constituted the core genome. After 2 mg L-1 or 0.75 × MIC polymyxin treatments for 15 min, 41 genes were commonly up-regulated, including those involved in membrane biogenesis and homeostasis, lipoprotein and phospholipid trafficking, efflux pump and poly-N-acetylglucosamine biosynthesis; six genes were commonly down-regulated, three of which were related to fatty acid biosynthesis. Additionally, comparison of the gene expression at 15 and 60 min in ATCC 19606 revealed that polymyxin treatment resulted in a rapid change in amino acid metabolism at 15 min and perturbations on envelope biogenesis at both time points. This is the first pan-transcriptomic study for polymyxin-treated A. baumannii and our results identified that the remodelled outer membrane, up-regulated efflux pumps and down-regulated fatty acid biosynthesis might be essential for early responses to polymyxins in A. baumannii. Our findings provide important mechanistic insights into bacterial responses to polymyxin killing and may facilitate the optimisation of polymyxin therapy against this problematic 'superbug'.

RevDate: 2020-05-29

Tschoeke D, Salazar VW, Vidal L, et al (2020)

Unlocking the Genomic Taxonomy of the Prochlorococcus Collective.

Microbial ecology pii:10.1007/s00248-020-01526-5 [Epub ahead of print].

Prochlorococcus is the most abundant photosynthetic prokaryote on our planet. The extensive ecological literature on the Prochlorococcus collective (PC) is based on the assumption that it comprises one single genus comprising the species Prochlorococcus marinus, containing itself a collective of ecotypes. Ecologists adopt the distributed genome hypothesis of an open pan-genome to explain the observed genomic diversity and evolution patterns of the ecotypes within PC. Novel genomic data for the PC prompted us to revisit this group, applying the current methods used in genomic taxonomy. As a result, we were able to distinguish the five genera: Prochlorococcus, Eurycolium, Prolificoccus, Thaumococcus, and Riococcus. The novel genera have distinct genomic and ecological attributes.

RevDate: 2020-05-29

Sharma P, Gupta SK, Barrett JB, et al (2020)

Comparison of Antimicrobial Resistance and Pan-Genome of Clinical and Non-Clinical Enterococcus cecorum from Poultry Using Whole-Genome Sequencing.

Foods (Basel, Switzerland), 9(6): pii:foods9060686.

Enterococcus cecorum is an emerging avian pathogen, particularly in chickens, but can be found in both diseased (clinical) and healthy (non-clinical) poultry. To better define differences between E. cecorum from the two groups, whole-genome sequencing (WGS) was used to identify and compare antimicrobial resistance genes as well as the pan-genome among the isolates. Eighteen strains selected from our previous study were subjected to WGS using Illumina MiSeq and comparatively analyzed. Assembled contigs were analyzed for resistance genes using ARG-ANNOT. Resistance to erythromycin was mediated by ermB, ermG, and mefA, in clinical isolates and ermB and mefA, in non-clinical isolates. Lincomycin resistance genes were identified as linB, lnuB, lnuC, and lnuD with lnuD found only in non-clinical E. cecorum; however, lnuB and linB were found in only one clinical isolate. For both groups of isolates, kanamycin resistance was mediated by aph3-III, while tetracycline resistance was conferred by tetM, tetO, and tetL. No mutations or known resistance genes were found for isolates resistant to either linezolid or chloramphenicol, suggesting possible new mechanisms of resistance to these drugs. A comparison of WGS results confirmed that non-clinical isolates contained more resistance genes than clinical isolates. The pan-genome of clinical and non-clinical isolates resulted in 3651 and 4950 gene families, respectively, whereas the core gene sets were comprised of 1559 and 1534 gene families in clinical and non-clinical isolates, respectively. Unique genes were found more frequently in non-clinical isolates than clinical. Phylogenetic analysis of the isolates and all the available complete and draft genomes showed no correlation between healthy and diseased poultry. Additional genomic comparison is required to elucidate genetic factors in E. cecorum that contribute to disease in poultry.

RevDate: 2020-05-28

Liu YH, Xie YG, Li L, et al (2020)

Cyclobacterium salsum sp. nov. and Cyclobacterium roseum sp. nov., isolated from a saline lake.

International journal of systematic and evolutionary microbiology [Epub ahead of print].

Two novel strains, designated SYSU L10167T and SYSU L10180T, were isolated from sediment sampled at Dabancheng saline lake in Xinjiang, PR China. A polyphasic approach was used to clarify the taxonomic positions of the two strains. Cells of the isolates were curved ring-like, horseshoe-shaped or rod-shaped, non-motile and non-spore-forming. Cells were Gram-stain-negative, aerobic, heterotrophic and rose-pigmented. The phylogenetic trees based on 16S rRNA gene sequences showed that strains SYSU L10167T and SYSU L10180T formed a distinct lineage within the genus Cyclobacterium. Strains SYSU L10167T and SYSU L10180T showed highest similarities to Cyclobacterium jeungdonense KCTC 23150T (98.0 and 97.4%, respectively). Results of genomic analyses (including average nucleotide identity, digital DNA-DNA hybridization and the marker gene tree) and pan-genome analysis further confirmed that strains SYSU L10167T and SYSU L10180T were separate from each other and other species of the genus Cyclobacterium. The draft genomes of the isolates had sizes of 5.5-5.7 Mb and reflected their major physiological capabilities. Based on phenotypic, physiological, chemotaxonomic and genotypic characterization, we propose that the isolates represent two novel species, for which the names Cyclobacterium salsum sp. nov. and Cyclobacterium roseum sp. nov. are proposed. The type strains of the species are SYSU L10167T (=KCTC 72390T=CGMCC 1.17521T) and SYSU L10180T (=KCTC 72391T=CGMCC 1.17278T).

RevDate: 2020-05-27

Garrido-Sanz D, Redondo-Nieto M, Martín M, et al (2020)

Comparative Genomics of the Rhodococcus Genus Shows Wide Distribution of Biodegradation Traits.

Microorganisms, 8(5): pii:microorganisms8050774.

The genus Rhodococcus exhibits great potential for bioremediation applications due to its huge metabolic diversity, including biotransformation of aromatic and aliphatic compounds. Comparative genomic studies of this genus are limited to a small number of genomes, while the high number of sequenced strains to date could provide more information about the Rhodococcus diversity. Phylogenomic analysis of 327 Rhodococcus genomes and clustering of intergenomic distances identified 42 phylogenomic groups and 83 species-level clusters. Rarefaction models show that these numbers are likely to increase as new Rhodococcus strains are sequenced. The Rhodococcus genus possesses a small "hard" core genome consisting of 381 orthologous groups (OGs), while a "soft" core genome of 1253 OGs is reached with 99.16% of the genomes. Models of sequentially randomly added genomes show that a small number of genomes are enough to explain most of the shared diversity of the Rhodococcus strains, while the "open" pangenome and strain-specific genome evidence that the diversity of the genus will increase, as new genomes still add more OGs to the whole genomic set. Most rhodococci possess genes involved in the degradation of aliphatic and aromatic compounds, while short-chain alkane degradation is restricted to a certain number of groups, among which a specific particulate methane monooxygenase (pMMO) is only found in Rhodococcus sp. WAY2. The analysis of Rieske 2Fe-2S dioxygenases among rhodococci genomes revealed that most of these enzymes remain uncharacterized.

RevDate: 2020-05-26

Eizenga JM, Novak AM, Sibbesen JA, et al (2020)

Pangenome Graphs.

Annual review of genomics and human genetics [Epub ahead of print].

Low-cost whole-genome assembly has enabled the collection of haplotype-resolved pangenomes for numerous organisms. In turn, this technological change is encouraging the development of methods that can precisely address the sequence and variation described in large collections of related genomes. These approaches often use graphical models of the pangenome to support algorithms for sequence alignment, visualization, functional genomics, and association studies. The additional information provided to these methods by the pangenome allows them to achieve superior performance on a variety of bioinformatic tasks, including read alignment, variant calling, and genotyping. Pangenome graphs stand to become a ubiquitous tool in genomics. Although it is unclear whether they will replace linear reference genomes, their ability to harmoniously relate multiple sequence and coordinate systems will make them useful irrespective of which pangenomic models become most common in the future. Expected final online publication date for the Annual Review of Genomics and Human Genetics, Volume 21 is August 31, 2020. Please see for revised estimates.

RevDate: 2020-05-26

Kelly LJ, Plumb WJ, Carey DW, et al (2020)

Convergent molecular evolution among ash species resistant to the emerald ash borer.

Nature ecology & evolution pii:10.1038/s41559-020-1209-3 [Epub ahead of print].

Recent studies show that molecular convergence plays an unexpectedly common role in the evolution of convergent phenotypes. We exploited this phenomenon to find candidate loci underlying resistance to the emerald ash borer (EAB, Agrilus planipennis), the United States' most costly invasive forest insect to date, within the pan-genome of ash trees (the genus Fraxinus). We show that EAB-resistant taxa occur within three independent phylogenetic lineages. In genomes from these resistant lineages, we detect 53 genes with evidence of convergent amino acid evolution. Gene-tree reconstruction indicates that, for 48 of these candidates, the convergent amino acids are more likely to have arisen via independent evolution than by another process such as hybridization or incomplete lineage sorting. Seven of the candidate genes have putative roles connected to the phenylpropanoid biosynthesis pathway and 17 relate to herbivore recognition, defence signalling or programmed cell death. Evidence for loss-of-function mutations among these candidates is more frequent in susceptible species than in resistant ones. Our results on evolutionary relationships, variability in resistance, and candidate genes for defence response within the ash genus could inform breeding for EAB resistance, facilitating ecological restoration in areas invaded by this beetle.

RevDate: 2020-05-25

Gao S, Wu J, Stiller J, et al (2020)

Identifying barley pan-genome sequence anchors using genetic mapping and machine learning.

TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik pii:10.1007/s00122-020-03615-y [Epub ahead of print].

KEY MESSAGE: We identified 1.844 million barley pan-genome sequence anchors from 12,306 genotypes using genetic mapping and machine learning. There is increasing evidence that genes from a given crop genotype are far to cover all genes in that species; thus, building more comprehensive pan-genomes is of great importance in genetic research and breeding. Obtaining a thousand-genotype scale pan-genome using deep-sequencing data is currently impractical for species like barley which has a huge and highly repetitive genome. To this end, we attempted to identify barley pan-genome sequence anchors from a large quantity of genotype-by-sequencing (GBS) datasets by combining genetic mapping and machine learning algorithms. Based on the GBS sequences from 11,166 domesticated and 1140 wild barley genotypes, we identified 1.844 million pan-genome sequence anchors. Of them, 532,253 were identified as presence/absence variation (PAV) tags. Through aligning these PAV tags to the genome of hulless barley genotype Zangqing320, our analysis resulted in a validation of 83.6% of them from the domesticated genotypes and 88.6% from the wild barley genotypes. Association analyses against flowering time, plant height and kernel size showed that the relative importance of the PAV and non-PAV tags varied for different traits. The pan-genome sequence anchors based on GBS tags can facilitate the construction of a comprehensive pan-genome and greatly assist various genetic studies including identification of structural variation, genetic mapping and breeding in barley.

RevDate: 2020-05-23

Oshkin IY, Miroshnikov KK, Grouzdev DS, et al (2020)

Pan-Genome-Based Analysis as a Framework for Demarcating Two Closely Related Methanotroph Genera Methylocystis and Methylosinus.

Microorganisms, 8(5): pii:microorganisms8050768.

The Methylocystis and Methylosinus are two of the five genera that were included in the first taxonomic framework of methanotrophic bacteria created half a century ago. Members of both genera are widely distributed in various environments and play a key role in reducing methane fluxes from soils and wetlands. The original separation of these methanotrophs in two distinct genera was based mainly on their differences in cell morphology. Further comparative studies that explored various single-gene-based phylogenies suggested the monophyletic nature of each of these genera. Current availability of genome sequences from members of the Methylocystis/ Methylosinus clade opens the possibility for in-depth comparison of the genomic potentials of these methanotrophs. Here, we report the finished genome sequence of Methylocystis heyeri H2T and compare it to 23 currently available genomes of Methylocystis and Methylosinus species. The phylogenomic analysis confirmed that members of these genera form two separate clades. The Methylocystis/Methylosinus pan-genome core comprised 1,173 genes, with the accessory genome containing 4,941 and 11,192 genes in the shell and the cloud, respectively. Major differences between the genome-encoded environmental traits of these methanotrophs include a variety of enzymes for methane oxidation and dinitrogen fixation as well as genomic determinants for cell motility and photosynthesis.

RevDate: 2020-05-21

Castillo AI, Chacón-Díaz C, Rodríguez-Murillo N, et al (2020)

Impacts of local population history and ecology on the evolution of a globally dispersed pathogen.

BMC genomics, 21(1):369 pii:10.1186/s12864-020-06778-6.

BACKGROUND: Pathogens with a global distribution face diverse biotic and abiotic conditions across populations. Moreover, the ecological and evolutionary history of each population is unique. Xylella fastidiosa is a xylem-dwelling bacterium infecting multiple plant hosts, often with detrimental effects. As a group, X. fastidiosa is divided into distinct subspecies with allopatric historical distributions and patterns of multiple introductions from numerous source populations. The capacity of X. fastidiosa to successfully colonize and cause disease in naïve plant hosts varies among subspecies, and potentially, among populations. Within Central America (i.e. Costa Rica) two X. fastidiosa subspecies coexist: the native subsp. fastidiosa and the introduced subsp. pauca. Using whole genome sequences, the patterns of gene gain/loss, genomic introgression, and genetic diversity were characterized within Costa Rica and contrasted to other X. fastidiosa populations.

RESULTS: Within Costa Rica, accessory and core genome analyses showed a highly malleable genome with numerous intra- and inter-subspecific gain/loss events. Likewise, variable levels of inter-subspecific introgression were found within and between both coexisting subspecies; nonetheless, the direction of donor/recipient subspecies to the recombinant segments varied. Some strains appeared to recombine more frequently than others; however, no group of genes or gene functions were overrepresented within recombinant segments. Finally, the patterns of genetic diversity of subsp. fastidiosa in Costa Rica were consistent with those of other native populations (i.e. subsp. pauca in Brazil).

CONCLUSIONS: Overall, this study shows the importance of characterizing local evolutionary and ecological history in the context of world-wide pathogen distribution.

RevDate: 2020-05-20

Fiuza TS, Lima JPMS, GA de Souza (2020)

EpitoCore: Mining Conserved Epitope Vaccine Candidates in the Core Proteome of Multiple Bacteria Strains.

Frontiers in immunology, 11:816.

In reverse vaccinology approaches, complete proteomes of bacteria are submitted to multiple computational prediction steps in order to filter proteins that are possible vaccine candidates. Most available tools perform such analysis only in a single strain, or a very limited number of strains. But the vast amount of genomic data had shown that most bacteria contain pangenomes, i.e., their genomic information contains core, conserved genes, and random accessory genes specific to each strain. Therefore, in reverse vaccinology methods it is of the utmost importance to define core proteins and core epitopes. EpitoCore is a decision-tree pipeline developed to fulfill that need. It provides surfaceome prediction of proteins from related strains, defines core proteins within those, calculate their immunogenicity, predicts epitopes for a given set of MHC alleles defined by the user, and then reports if epitopes are located extracellularly and if they are conserved among the core homologs. Pipeline performance is illustrated by mining peptide vaccine candidates in Mycobacterium avium hominissuis strains. From a total proteome of ~4,800 proteins per strain, EpitoCore predicted 103 highly immunogenic core homologs located at cell surface, many of those related to virulence and drug resistance. Conserved epitopes identified among these homologs allows the users to define sets of peptides with potential to immunize the largest coverage of tested HLA alleles using peptide-based vaccines. Therefore, EpitoCore is able to provide automated identification of conserved epitopes in bacterial pangenomic datasets.

RevDate: 2020-05-19

Gohil K, Rajput V, M Dharne (2020)

Pan-genomics of Ochrobactrum species from clinical and environmental origins reveals distinct populations and possible links.

Genomics pii:S0888-7543(19)30993-0 [Epub ahead of print].

Ochrobactrum genus is comprised of soil-dwelling Gram-negative bacteria mainly reported for bioremediation of toxic compounds. Since last few years, mainly two species of this genus, O. intermedium and O. anthropi were documented for causing infections mostly in the immunocompromised patients. Despite such ubiquitous presence, study of adaptation in various niches is still lacking. Thus, to gain insights into the niche adaptation strategies, pan-genome analysis was carried out by comparing 67 genome sequences belonging to Ochrobactrum species. Pan-genome analysis revealed it is an open pan-genome indicative of the continuously evolving nature of the genus. The presence/absence of gene clusters also illustrated the unique presence of antibiotic efflux transporter genes and type IV secretion system genes in the clinical strains while the genes of solvent resistance and exporter pumps in the environmental strains. A phylogenomic investigation based on 75 core genes depicted better and robust phylogenetic resolution and topology than the 16S rRNA gene. To support the pan-genome analysis, individual genomes were also investigated for the mobile genetic elements (MGE), antibiotic resistance genes (ARG), metal resistance genes (MRG) and virulence factors (VF). The analysis revealed the presence of MGE, ARG, and MRG in all the strains which play an important role in the species evolution which is in agreement with the pan-genome analysis. The average nucleotide identity (ANI) based on the genetic relatedness between the Ochrobactrum species indicated a distinction between individual species. Interestingly, the ANI tool was able to classify the Ochrobactrum genomes to the species level which were assigned till the genus level on the NCBI database.

RevDate: 2020-05-19

Katiyar A, Sharma P, Dahiya S, et al (2020)

Genomic profiling of antimicrobial resistance genes in clinical isolates of Salmonella Typhi from patients infected with Typhoid fever in India.

Scientific reports, 10(1):8299 pii:10.1038/s41598-020-64934-0.

The development of multidrug resistance in Salmonella enterica serovar Typhi currently forms a major roadblock for the treatment of enteric fever. This poses a major health problem in endemic regions and extends to travellers returning from developing countries. The appearance of fluoroquinolone non-susceptible strains has resulted in use of ceftriaxone as drug of choice with azithromycin being recommended for uncomplicated cases of typhoid fever. A recent sporadic instance of decreased susceptibility to the latest drug regime has necessitated a detailed analysis of antimicrobial resistance genes and possible relationships with their phenotypes to facilitate selection of future treatment regimes. Whole genome sequencing (WGS) was conducted for 133 clinical isolates from typhoid patients. Sequence output files were processed for pan-genome analysis and prediction of antimicrobial resistance genes. The WGS analyses disclosed the existence of fluoroquinolone resistance conferring mutations in gyrA, gyrB, parC and parE genes of all strains. Acquired resistance determining mechanisms observed included catA1 genes for chloramphenicol resistance, dfrA7, dfrA15, sul1 and sul2 for trimethoprim-sulfamethoxazole and blaTEM-116/blaTEM-1B genes for amoxicillin. No resistance determinants were found for ceftriaxone and cefixime. The genotypes were further correlated with their respective phenotypes for chloramphenicol, ampicillin, co-trimoxazole, ciprofloxacin and ceftriaxone. A high correlation was observed between genotypes and phenotypes in isolates of S. Typhi. The pan-genome analysis revealed that core genes were enriched in metabolic functions and accessory genes were majorly implicated in pathogenesis and antimicrobial resistance. The pan-genome of S. Typhi appears to be closed (Bpan = 0.09) as analysed by Heap's law. Simpson's diversity index of 0.51 showed a lower level of genetic diversity among isolates of S. Typhi. Overall, this study augments the present knowledge that WGS can help predict resistance genotypes and eventual correlation with phenotypes, enabling the chance to spot AMR determinants for fast diagnosis and prioritize antibiotic use directly from sequence.

RevDate: 2020-05-19

Datta S, Saha D, Chattopadhyay L, et al (2020)

Genome Comparison Identifies Different Bacillus Species in a Bast Fibre-Retting Bacterial Consortium and Provides Insights into Pectin Degrading Genes.

Scientific reports, 10(1):8169 pii:10.1038/s41598-020-65228-1.

Retting of bast fibres requires removal of pectin, hemicellulose and other non-cellulosic materials from plant stem tissues by a complex microbial community. A microbial retting consortium with high-efficiency pectinolytic bacterial strains is effective in reducing retting-time and enhancing fibre quality. We report comprehensive genomic analyses of three bacterial strains (PJRB 1, 2 and 3) of the consortium and resolve their taxonomic status, genomic features, variations, and pan-genome dynamics. The genome sizes of the strains are ~3.8 Mb with 3729 to 4002 protein-coding genes. Detailed annotations of the protein-coding genes revealed different carbohydrate-degrading CAZy classes viz. PL1, PL9, GH28, CE8, and CE12. Phylogeny and structural features of pectate lyase proteins of PJRB strains divulge their functional uniqueness and evolutionary convergence with closely related Bacillus strains. Genome-wide prediction of genomic variations revealed 12461 to 67381 SNPs, and notably many unique SNPs were localized within the important pectin metabolism genes. The variations in the pectate lyase genes possibly contribute to their specialized pectinolytic function during the retting process. These findings encompass a strong foundation for fundamental and evolutionary studies on this unique microbial degradation of decaying plant material with immense industrial significance. These have preponderant implications in plant biomass research and food industry, and also posit application in the reclamation of water pollution from plant materials.

RevDate: 2020-05-18

Huang CH, Chen CC, Liou JS, et al (2020)

Genome-based reclassification of Lactobacillus casei: emended classification and description of the species Lactobacillus zeae.

International journal of systematic and evolutionary microbiology [Epub ahead of print].

Taxonomic relationships between Lactobacillus casei, Lactobacillus paracasei and Lactobacillus zeae have long been debated. Results of previous analyses have shown that overall genome relatedness indices (such as average nucleotide identity and core nucleotide identity) between the type strains L. casei ATCC 393T and L. zeae ATCC 15820T were 94.6 and 95.3 %, respectively, which are borderline for species definition. However, the digital DNA‒DNA hybridization value was 57.3 %, which was clearly lower than the species delineation threshold of 70 %, and hence raised the possibility that L. casei could be reclassified into two species. To re-evaluate the taxonomic relationship of these taxa, multilocus sequence analysis (MLSA) based on the concatenated five housekeeping gene (dnaJ, dnaK, mutL, pheS and yycH) sequences, phylogenomic and core genome multilocus sequence typing analyses, gene presence and absence profiles using pan-genome analysis, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) profiling analysis, cellular fatty acid compositions, and phenotype analysis were carried out. The results of phenotypic characterization, MLSA, whole-genome sequence-based analyses and MALDI-TOF MS profiling justified an independent species designation for the L. zeae strains, and supported an emended the description of the name of Lactobacillus zeae (ex Kuznetsov 1956) Dicks et al. 1996, with ATCC 15820T (=DSM 20178T=BCRC 17942T) as the type strain.

RevDate: 2020-05-14

Bakhshi Ganje M, Mackay J, Nicolaisen M, et al (2020)

Comparative Genomics, Pangenome and Phylogenomic Analyses of the Brenneria spp., Delineation of the Brenneria izadpanahii sp. nov.

Phytopathology [Epub ahead of print].

Brenneria species are bacterial plant pathogens mainly affecting woody plants. Association of all members with devastating disorders (e. g. acute oak decline in Iran and UK) are due to adaptation and pathogenic behavior in response to host and environmental factors. Some species, including B. goodwinii, B. salicis and B. nigrifluens, also show endophytic residence. Here we show that all species including novel Brenneria sp. are closely related. Gene-based and genome/pangenome-based phylogeny divide the genus into two distinct lineages, Brenneria clade A and B. The two clades were functionally distinct and were consistent with their common and special potential activities as determined via annotation of functional domains. Pangenome analysis demonstrated that the core pathogenicity factors were highly conserved, a hrp gene cluster encoding a type III secretion system was found in all species except B. corticis. An extensive repertoire of candidate virulence factors was identified. Comparative genomics indicated a repertoire of plant cell wall degrading enzymes (PCDWs), metabolites/antibiotics, and numerous prophages providing new insights into Brenneria-host interactions and appropriate targets for further characterization. This work not only documented the genetic differentiation of Brenneria species but also delineates a more functionally driven understanding of Brenneria by comparison with relevant Pectobacteriaceae thereby substantially enriching the extent of information available for functional genomic investigations.

RevDate: 2020-05-14

Wang M, Zhu H, Kong Z, et al (2020)

Pan-Genome Analyses of Geobacillus spp. Reveal Genetic Characteristics and Composting Potential.

International journal of molecular sciences, 21(9): pii:ijms21093393.

The genus Geobacillus is abundant in ecological diversity and is also well-known as an authoritative source for producing various thermostable enzymes. Although it is clear now that Geobacillus evolved from Bacillus, relatively little knowledge has been obtained regarding its evolutionary mechanism, which might also contribute to its ecological diversity and biotechnology potential. Here, a statistical comparison of thirty-two Geobacillus genomes was performed with a specific focus on pan- and core genomes. The pan-genome of this set of Geobacillus strains contained 14,913 genes, and the core genome contained 940 genes. The Clusters of Orthologous Groups (COG) and Carbohydrate-Active Enzymes (CAZymes) analysis revealed that the Geobacillus strains had huge potential industrial application in composting for agricultural waste management. Detailed comparative analyses showed that basic functional classes and housekeeping genes were conserved in the core genome, while genes associated with environmental interaction or energy metabolism were more enriched in the pan-genome. Therefore, the evolution of Geobacillus seems to be guided by environmental parameters. In addition, horizontal gene transfer (HGT) events among different Geobacillus species were detected. Altogether, pan-genome analysis was a useful method for detecting the evolutionary mechanism, and Geobacillus' evolution was directed by the environment and HGT events.

RevDate: 2020-05-12

Chibani CM, Roth O, Liesegang H, et al (2020)

Genomic variation among closely related Vibrio alginolyticus strains is located on mobile genetic elements.

BMC genomics, 21(1):354 pii:10.1186/s12864-020-6735-5.

BACKGROUND: Species of the genus Vibrio, one of the most diverse bacteria genera, have undergone niche adaptation followed by clonal expansion. Niche adaptation and ultimately the formation of ecotypes and speciation in this genus has been suggested to be mainly driven by horizontal gene transfer (HGT) through mobile genetic elements (MGEs). Our knowledge about the diversity and distribution of Vibrio MGEs is heavily biased towards human pathogens and our understanding of the distribution of core genomic signatures and accessory genes encoded on MGEs within specific Vibrio clades is still incomplete. We used nine different strains of the marine bacterium Vibrio alginolyticus isolated from pipefish in the Kiel-Fjord to perform a multiscale-comparative genomic approach that allowed us to investigate [1] those genomic signatures that characterize a habitat-specific ecotype and [2] the source of genomic variation within this ecotype.

RESULTS: We found that the nine isolates from the Kiel-Fjord have a closed-pangenome and did not differ based on core-genomic signatures. Unique genomic regions and a unique repertoire of MGEs within the Kiel-Fjord isolates suggest that the acquisition of gene-blocks by HGT played an important role in the evolution of this ecotype. Additionally, we found that ~ 90% of the genomic variation among the nine isolates is encoded on MGEs, which supports ongoing theory that accessory genes are predominately located on MGEs and shared by HGT. Lastly, we could show that these nine isolates share a unique virulence and resistance profile which clearly separates them from all other investigated V. alginolyticus strains and suggests that these are habitat-specific genes, required for a successful colonization of the pipefish, the niche of this ecotype.

CONCLUSION: We conclude that all nine V. alginolyticus strains from the Kiel-Fjord belong to a unique ecotype, which we named the Kiel-alginolyticus ecotype. The low sequence variation of the core-genome in combination with the presence of MGE encoded relevant traits, as well as the presence of a suitable niche (here the pipefish), suggest, that this ecotype might have evolved from a clonal expansion following HGT driven niche-adaptation.

RevDate: 2020-05-10

Molina L, Segura A, Duque E, et al (2020)

The versatility of Pseudomonas putida in the rhizosphere environment.

Advances in applied microbiology, 110:149-180.

This article addresses the lifestyle of Pseudomonas and focuses on how Pseudomonas putida can be used as a model system for biotechnological processes in agriculture, and in the removal of pollutants from soils. In this chapter we aim to show how a deep analysis using genetic information and experimental tests has helped to reveal insights into the lifestyle of Pseudomonads. Pseudomonas putida is a Plant Growth Promoting Rhizobacteria (PGPR) that establishes commensal relationships with plants. The interaction involves a series of functions encoded by core genes which favor nutrient mobilization, prevention of pathogen development and efficient niche colonization. Certain Pseudomonas putida strains harbor accessory genes that confer specific biodegradative properties and because these microorganisms can thrive on the roots of plants they can be exploited to remove pollutants via rhizoremediation, making the consortium plant/Pseudomonas a useful tool to combat pollution.

RevDate: 2020-05-08

Kim YB, Kim JY, Song HS, et al (2020)

Haloplanus rubicundus sp. nov., an extremely halophilic archaeon isolated from solar salt.

Systematic and applied microbiology pii:S0723-2020(20)30036-9 [Epub ahead of print].

Two extremely halophilic archaea strains, CBA1112T and CBA1113, were isolated from solar salt in Korea. The genome sizes and G+C content of CBA1112T and CBA1113 were 3.77 and 3.53Mb, and 66.0 and 66.5mol%, respectively. Phylogenetic analysis based on closely related taxa and environmental Haloplanus sequences indicated that both CBA1112T and CBA1113 strains are grouped within the genus Haloplanus. OrthoANI and in silico DNA-DNA hybridization values were below the species delineation threshold. Pan-genomic analysis showed that the two novel strains and four reference strains had 6203 pan-orthologous groups in total. Six Haloplanus strains shared 1728 core pan-genome orthologous groups, which were mainly associated with amino acid transport and metabolism and translation, ribosomal structure and biogenesis categories, and amino acid metabolism and carbohydrate metabolism related categories. The novel strain-specific pan-genome orthologous groups were mainly involved with replication, recombination and repair category and replication and repair pathway or amino acid metabolism pathway. Cells of both strains were Gram-negative and pleomorphic, and colonies were red-pigmented. The major polar lipids of both strains were phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, phosphatidylglycerol sulfate, and one glycolipid, sulfated mannosyl glucosyl diether. Based on genomic, phylogenetic, phenotypic, and chemotaxonomic features, strains CBA1112T and CBA1113 are described as novel species of the genus Haloplanus. Thus, we propose the name Haloplanus rubicundus sp. nov. The type strain is CBA1112T (=KCCM 43224T=JCM 30475T).

RevDate: 2020-05-07

Gladstone RA, Lo SW, Goater R, et al (2020)

Visualizing variation within Global Pneumococcal Sequence Clusters (GPSCs) and country population snapshots to contextualize pneumococcal isolates.

Microbial genomics [Epub ahead of print].

Knowledge of pneumococcal lineages, their geographic distribution and antibiotic resistance patterns, can give insights into global pneumococcal disease. We provide interactive bioinformatic outputs to explore such topics, aiming to increase dissemination of genomic insights to the wider community, without the need for specialist training. We prepared 12 country-specific phylogenetic snapshots, and international phylogenetic snapshots of 73 common Global Pneumococcal Sequence Clusters (GPSCs) previously defined using PopPUNK, and present them in Microreact. Gene presence and absence defined using Roary, and recombination profiles derived from Gubbins are presented in Phandango for each GPSC. Temporal phylogenetic signal was assessed for each GPSC using BactDating. We provide examples of how such resources can be used. In our example use of a country-specific phylogenetic snapshot we determined that serotype 14 was observed in nine unrelated genetic backgrounds in South Africa. The international phylogenetic snapshot of GPSC9, in which most serotype 14 isolates from South Africa were observed, highlights that there were three independent sub-clusters represented by South African serotype 14 isolates. We estimated from the GPSC9-dated tree that the sub-clusters were each established in South Africa during the 1980s. We show how recombination plots allowed the identification of a 20 kb recombination spanning the capsular polysaccharide locus within GPSC97. This was consistent with a switch from serotype 6A to 19A estimated to have occured in the 1990s from the GPSC97-dated tree. Plots of gene presence/absence of resistance genes (tet, erm, cat) across the GPSC23 phylogeny were consistent with acquisition of a composite transposon. We estimated from the GPSC23-dated tree that the acquisition occurred between 1953 and 1975. Finally, we demonstrate the assignment of GPSC31 to 17 externally generated pneumococcal serotype 1 assemblies from Utah via Pathogenwatch. Most of the Utah isolates clustered within GPSC31 in a USA-specific clade with the most recent common ancestor estimated between 1958 and 1981. The resources we have provided can be used to explore to data, test hypothesis and generate new hypotheses. The accessible assignment of GPSCs allows others to contextualize their own collections beyond the data presented here.

RevDate: 2020-05-07

Bu QT, Li YP, Xie H, et al (2020)

Comprehensive dissection of dispensable genomic regions in Streptomyces based on comparative analysis approach.

Microbial cell factories, 19(1):99 pii:10.1186/s12934-020-01359-4.

BACKGROUND: Large-scale genome reduction has been performed to significantly improve the performance of microbial chassis. Identification of the essential or dispensable genes is pivotal for genome reduction to avoid synthetic lethality. Here, taking Streptomyces as an example, we developed a combinatorial strategy for systematic identification of large and dispensable genomic regions in Streptomyces based on multi-omics approaches.

RESULTS: Phylogenetic tree analysis revealed that the model strains including S. coelicolor A3(2), S. albus J1074 and S. avermitilis MA-4680 were preferred reference for comparative analysis of candidate genomes. Multiple genome alignment suggested that the Streptomyces genomes embodied highly conserved core region and variable sub-telomeric regions, and may present symmetric or asymmetric structure. Pan-genome and functional genome analyses showed that most conserved genes responsible for the fundamental functions of cell viability were concentrated in the core region and the vast majority of abundant genes were dispersed in the sub-telomeric regions. These results suggested that large-scale deletion can be performed in sub-telomeric regions to greatly streamline the Streptomyces genomes for developing versatile chassis.

CONCLUSIONS: The integrative approach of comparative genomics, functional genomics and pan-genomics can not only be applied to perform a multi-tiered dissection for Streptomyces genomes, but also work as a universal method for systematic analysis of removable regions in other microbial hosts in order to generate more miscellaneous and versatile chassis with minimized genome for drug discovery.

RevDate: 2020-05-06

Zwarycz AS, Livingstone PG, DE Whitworth (2020)

Within-species variation in OMV cargo proteins: the Myxococcus xanthus OMV pan-proteome.

Molecular omics [Epub ahead of print].

Extracellular membrane vesicles are produced by all domains of life (bacteria, archaea and eukaryotes). Bacterial extracellular vesicles (outer membrane vesicles or OMVs) are produced by outer membrane blebbing, and contain proteins, nucleic acids, virulence factors, lipids and metabolites. OMV functions depend on their internal composition, therefore understanding the proteome of OMVs, and how it varies between organisms, is imperative. Here, we report a comparative proteomic profiling of OMVs from strains of Myxococcus xanthus, a predatory species of Gram-negative myxobacteria whose secretions include secondary metabolites and hydrolytic enzymes, thought to be involved in prey lysis. Ten strains were chosen for study, of which seven had genome sequences available. The remaining three strains were genome sequenced allowing definition of the core and accessory genes and genome-derived proteins found within the pan-genome and pan-proteome respectively. OMVs were isolated from each strain and proteins identified using mass spectrometry. The M. xanthus OMV pan-proteome was found to contain tens of 'core' and hundreds of 'accessory' proteins. Properties of the OMV pan-proteome were compared with those of the pan-proteome deduced from the M. xanthus pan-genome. On average, 80% of 'core' OMV proteins are encoded by genes of the core genome, yet the OMV proteomes of individual strains contain subsets of core genome-derived proteins which only partially overlap. In addition, the distribution of characteristics of vesicle proteins does not correlate with the genome-derived proteome characteristic distribution. We hypothesize that M. xanthus cells package a personalized subset of proteins whose availability is only partially dictated by the presence/absence of encoding genes within the genome.

RevDate: 2020-05-06

Garcia-Gutierrez E, Walsh CJ, Sayavedra L, et al (2020)

Genotypic and Phenotypic Characterization of Fecal Staphylococcus epidermidis Isolates Suggests Plasticity to Adapt to Different Human Body Sites.

Frontiers in microbiology, 11:688.

Staphylococcus epidermidis is a commensal species that has been increasingly identified as a nosocomial agent. Despite the interest, little is known about the ability of S. epidermidis isolates to adapt to different ecological niches through comparisons at genotype or phenotype levels. One niche where S. epidermidis has been reported is the human gut. Here, we present three S. epidermidis strains isolated from feces and show that they are not phylogenetically distinct from S. epidermidis isolated from other human body sites. Both gut and skin strains harbored multiple genes associated with biofilm formation and showed similar levels of biofilm formation on abiotic surfaces. High-throughput physiological tests using the BIOLOG technology showed no major metabolic differences between isolates from stool, skin, or cheese, while an isolate from bovine mastitis showed more phenotypic variation. Gut and skin isolates showed the ability to metabolize glycine-conjugated bile acids and to grow in the presence of bile, but the gut isolates exhibited faster anaerobic growth compared to isolates of skin origin.

RevDate: 2020-05-04

Zhang Y, Wang J, Yajun C, et al (2020)

Comparative Genomics Uncovers the Genetic Diversity and Synthetic Biology of Secondary Metabolite Production of Trametes.

Mycobiology, 48(2):104-114 pii:1725361.

The carbohydrate-active enzyme (CAZyme) genes of Trametes contribute to polysaccharide degradation. However, the comprehensive analysis of the composition of CAZymes and the biosynthetic gene clusters (BGCs) of Trametes remain unclear. Here, we conducted comparative analysis, detected the CAZyme genes, and predicted the BGCs for nine Trametes strains. Among the 82,053 homologous clusters obtained for Trametes, we identified 8518 core genes, 60,441 accessory genes, and 13,094 specific genes. A large proportion of CAZyme genes were cataloged into glycoside hydrolases, glycosyltransferases, and carbohydrate esterases. The predicted BGCs of Trametes were divided into six strategies, and the nine Trametes strains harbored 47.78 BGCs on average. Our study revealed that Trametes exhibits an open pan-genome structure. These findings provide insights into the genetic diversity and explored the synthetic biology of secondary metabolite production for Trametes.

RevDate: 2020-05-03

Farin W, Oñate FP, Plassais J, et al (2020)

Impact of laparoscopic Roux-en-Y gastric bypass and sleeve gastrectomy on gut microbiota: a metagenomic comparative analysis.

Surgery for obesity and related diseases : official journal of the American Society for Bariatric Surgery pii:S1550-7289(20)30132-5 [Epub ahead of print].

BACKGROUND: Bariatric surgery is an effective therapeutic procedure for morbidly obese patients. The 2 most common interventions are sleeve gastrectomy (SG) and laparoscopic Roux-en-Y gastric bypass (LRYGB).

OBJECTIVES: The aim of this study was to compare microbiome long-term microbiome after SG and LRYGB surgery in obese patients.

SETTING: University Hospital, France; University Hospital, United States; and University Hospital, Switzerland.

METHODS: Eighty-nine and 108 patients who underwent SG and LRYGB, respectively, were recruited. Stools were collected before and 6 months after surgery. Microbial DNA was analyzed with shotgun metagenomic sequencing (SOLiD 5500 xl Wildfire). MSPminer, a novel innovative tool to characterize new in silico biological entities, was used to identify 715 Metagenomic Species Pan-genome. One hundred forty-eight functional modules were analyzed using GOmixer and KEGG database.

RESULTS: Both interventions resulted in a similar increase of Shannon's diversity index and gene richness of gut microbiota, in parallel with weight loss, but the changes of microbial composition were different. LRYGB led to higher relative abundance of aero-tolerant bacteria, such as Escherichia coli and buccal species, such as Streptococcus and Veillonella spp. In contrast, anaerobes, such as Clostridium, were more abundant after SG, suggesting better conservation of anaerobic conditions in the gut. Enrichment of Akkermansia muciniphila was also observed after both surgeries. Function-level changes included higher potential for bacterial use of supplements, such as vitamin B12, B1, and iron upon LRYGB.

CONCLUSION: Microbiota changes after bariatric surgery depend on the nature of the intervention. LRYGB induces greater taxonomic and functional changes in gut microbiota than SG. Possible long-term health consequences of these alterations remain to be established.

RevDate: 2020-05-01

Li J, Gu T, Li L, et al (2020)

Complete genome sequencing and comparative genomic analyses of Bacillus sp. S3, a novel hyper Sb(III)-oxidizing bacterium.

BMC microbiology, 20(1):106 pii:10.1186/s12866-020-01737-3.

BACKGROUND: Antimonite [Sb(III)]-oxidizing bacterium has great potential in the environmental bioremediation of Sb-polluted sites. Bacillus sp. S3 that was previously isolated from antimony-contaminated soil displayed high Sb(III) resistance and Sb(III) oxidation efficiency. However, the genomic information and evolutionary feature of Bacillus sp. S3 are very scarce.

RESULTS: Here, we identified a 5,436,472 bp chromosome with 40.30% GC content and a 241,339 bp plasmid with 36.74% GC content in the complete genome of Bacillus sp. S3. Genomic annotation showed that Bacillus sp. S3 contained a key aioB gene potentially encoding As (III)/Sb(III) oxidase, which was not shared with other Bacillus strains. Furthermore, a wide variety of genes associated with Sb(III) and other heavy metal (loid) s were also ascertained in Bacillus sp. S3, reflecting its adaptive advantage for growth in the harsh eco-environment. Based on the analysis of phylogenetic relationship and the average nucleotide identities (ANI), Bacillus sp. S3 was proved to a novel species within the Bacillus genus. The majority of mobile genetic elements (MGEs) mainly distributed on chromosomes within the Bacillus genus. Pan-genome analysis showed that the 45 genomes contained 554 core genes and many unique genes were dissected in analyzed genomes. Whole genomic alignment showed that Bacillus genus underwent frequently large-scale evolutionary events. In addition, the origin and evolution analysis of Sb(III)-resistance genes revealed the evolutionary relationships and horizontal gene transfer (HGT) events among the Bacillus genus. The assessment of functionality of heavy metal (loid) s resistance genes emphasized its indispensable role in the harsh eco-environment of Bacillus genus. Real-time quantitative PCR (RT-qPCR) analysis indicated that Sb(III)-related genes were all induced under the Sb(III) stress, while arsC gene was down-regulated.

CONCLUSIONS: The results in this study shed light on the molecular mechanisms of Bacillus sp. S3 coping with Sb(III), extended our understanding on the evolutionary relationships between Bacillus sp. S3 and other closely related species, and further enriched the Sb(III) resistance genetic data sources.

RevDate: 2020-04-27

Kim E, Yang SM, Cho EJ, et al (2020)

Novel real-time PCR assay for Lactobacillus casei group species using comparative genomics.

Food microbiology, 90:103485.

The Lactobacillus casei group, which includes the closely related species L. casei, L. paracasei, L. rhamnosus, and L. chiayiensis, has been under debate regarding its taxonomy because of the difficulty in distinguishing the species from each other. In the present study, we developed a novel real-time PCR assay for distinguishing the L. casei group species. The pan-genome, as determined by the genomes of 44 strains, comprised 6789 genes, comparative genomic analysis showed that L. casei group strains were classified by species. Based on these results, species-specific genes were identified, and primers were designed from those genes. Real-time PCR clearly distinguished each species of the L. casei group and specifically amplified only to the target species. The method was applied to 29 probiotic products, and the detected results and label claims were compared. Total 23 products were in accordance with the label claims, and the remaining products contained species different from those stated in the label claims. Our method can rapidly and accurately distinguish the L. casei group species in a single reaction. Hence, our assay can be applied to identify L. casei group species from food or environmental samples and to accurately determine the nomenclature of the species.

RevDate: 2020-04-25

Bickhart DM, McClure JC, Schnabel RD, et al (2020)

Symposium review: Advances in sequencing technology herald a new frontier in cattle genomics and genome-enabled selection.

Journal of dairy science pii:S0022-0302(20)30311-8 [Epub ahead of print].

The cattle reference genome assembly has underpinned major innovations in beef and dairy genetics through genome-enabled selection, including removal of deleterious recessive variants and selection for favorable alleles affecting quantitative production traits. The initial reference assemblies, up to and including UMD3.1 and Btau4.1, were based on a combination of clone-by-clone sequencing of bacterial artificial chromosome clones generated from blood DNA of a Hereford bull and whole-genome shotgun sequencing of blood DNA from his inbred daughter/granddaughter named L1 Dominette 01449 (Dominette). The approach introduced assembly gaps, misassemblies, and errors, and it limited the ability to assemble regions that undergo rearrangement in blood cells, such as immune gene clusters. Nonetheless, the reference supported the creation of genotyping tools and provided a basis for many studies of gene expression. Recently, long-read sequencing technologies have emerged that facilitated a re-assembly of the reference genome, using lung tissue from Dominette to resolve many of the problems and providing a bridge to place historical studies in common context. The new reference, ARS-UCD1.2, successfully assembled germline immune gene clusters and improved overall continuity (i.e., reduction of gaps and inversions) by over 250-fold. This reference properly places nearly all of the legacy genetic markers used for over a decade in the industry. In this review, we discuss the improvements made to the cattle reference; remaining issues present in the assembly; tools developed to support genome-based studies in beef and dairy cattle; and the emergence of newer genome assembly methods that are producing even higher-quality assemblies for other breeds of cattle at a fraction of the cost. The new frontier for cattle genomics research will likely include a transition from the individual Hereford reference genome, to a "pan-genome" reference, representing all the DNA segments existing in commonly used cattle breeds, bringing the cattle reference into line with the current direction of human genome research.

RevDate: 2020-04-22

Guillier L, Gourmelon M, Lozach S, et al (2020)

AB_SA: Accessory genes-Based Source Attribution - tracing the source of Salmonella enterica Typhimurium environmental strains.

Microbial genomics [Epub ahead of print].

The partitioning of pathogenic strains isolated in environmental or human cases to their sources is challenging. The pathogens usually colonize multiple animal hosts, including livestock, which contaminate the food-production chain and the environment (e.g. soil and water), posing an additional public-health burden and major challenges in the identification of the source. Genomic data opens up new opportunities for the development of statistical models aiming to indicate the likely source of pathogen contamination. Here, we propose a computationally fast and efficient multinomial logistic regression source-attribution classifier to predict the animal source of bacterial isolates based on 'source-enriched' loci extracted from the accessory-genome profiles of a pangenomic dataset. Depending on the accuracy of the model's self-attribution step, the modeller selects the number of candidate accessory genes that best fit the model for calculating the likelihood of (source) category membership. The Accessory genes-Based Source Attribution (AB_SA) method was applied to a dataset of strains of Salmonella enterica Typhimurium and its monophasic variant (S. enterica 1,4,[5],12:i:-). The model was trained on 69 strains with known animal-source categories (i.e. poultry, ruminant and pig). The AB_SA method helped to identify 8 genes as predictors among the 2802 accessory genes. The self-attribution accuracy was 80 %. The AB_SA model was then able to classify 25 of the 29 S. enterica Typhimurium and S. enterica 1,4,[5],12:i:- isolates collected from the environment (considered to be of unknown source) into a specific category (i.e. animal source), with more than 85 % of probability. The AB_SA method herein described provides a user-friendly and valuable tool for performing source-attribution studies in only a few steps. AB_SA is written in R and freely available at

RevDate: 2020-04-20

Teixeira P, Tacão M, Baraúna RA, et al (2020)

Genomic analysis of Chromobacterium haemolyticum: insights into the species resistome, virulence determinants and genome plasticity.

Molecular genetics and genomics : MGG pii:10.1007/s00438-020-01676-8 [Epub ahead of print].

The increasing number of Chromobacterium haemolyticum human infection reports, especially in tropical regions and connected with environmental sources, resulted in an urge to better describe this species. This study aimed to characterize the C. haemolyticum resistome, virulence determinants and genetic platforms related with genome plasticity. A comparative genomic analysis was conducted between clinical C. haemolyticum genomes publicly available and the genome of an environmental isolate obtained in this study. The pangenome of C. haemolyticum was calculated and a total of 3378 core genes were predicted in its core genome, corresponding to 51.7% of the pangenome. Genetic determinants putatively encoding resistance to beta-lactams, fosfomycin, aminoglycosides and trimethoprim were predicted in all genomes, possibly constituting the intrinsic resistome of this species. In terms of resistance to beta-lactams, 4 genes were predicted encoding beta-lactamases of classes A, C and D. Moreover, the analysis of Chromobacterium genomes and C. haemolyticum environmental isolates reinforced the role of this genus as progenitor of the blaKPC gene. Putative virulence factors (VFs) were predicted in all genomes, related to adherence, toxins production, colonization and cell invasion. Secretion systems, including type III, were detected. A significant number of transposases and genomic islands were predicted in C. haemolyticum, in some cases above the average reported for Gram-negative bacterial genomes. We conclude that C. haemolyticum strains, including those of environmental origin, present a noteworthy collection of antibiotic resistance genes and VFs. Furthermore, sequences related to gene mobility and genome plasticity suggest high adaptability potential and a possible role as disseminator of antibiotic resistance.

RevDate: 2020-04-17

Gounot JS, Neuvéglise C, Freel KC, et al (2020)

High complexity and degree of genetic variation in Brettanomyces bruxellensis population.

Genome biology and evolution pii:5821423 [Epub ahead of print].

Genome-wide characterization of genetic variants of a large population of individuals within the same species is essential to have a deeper insight into its evolutionary history as well as the genotype-phenotype relationship. Population genomic surveys have been performed in multiple yeast species, including the two model organisms, Saccharomyces cerevisiae and Schizosaccharomyces pombe. In this context, we sought to characterize at the population level the Brettanomyces bruxellensis yeast species, which is a major cause of wine spoilage but also can contribute to the specific flavor profile of some Belgium beers. We have completely sequenced the genome of 53 B. bruxellensis strains isolated worldwide. The annotation of the reference genome allowed us to define the gene content of this species. As previously suggested, our genomic data clearly highlighted that genetic diversity variation is related to ploidy level, which is variable in the B. bruxellensis species. Genomes are punctuated by multiple loss-of-heterozygosity regions while aneuploidies as well as segmental duplications are uncommon. Interestingly, triploid genomes are more prone to gene copy number variation than diploids. Finally, the pangenome of the species was reconstructed and was found to be small with few accessory genes compared to S. cerevisiae. The pangenome is composed of 5,409 ORFs among which 5,106 core ORFs and 303 ORFs that are variable within the population. All these results highlight the different trajectories of species evolution and consequently the interest of establishing population genomic surveys in more populations.

RevDate: 2020-04-17

Dziadkiewicz P, N Dojer (2020)

Getting insight into the pan-genome structure with PangTree.

BMC genomics, 21(Suppl 2):274 pii:10.1186/s12864-020-6610-4.

BACKGROUND: The term pan-genome was proposed to denominate collections of genomic sequences jointly analyzed or used as a reference. The constant growth of genomic data intensifies development of data structures and algorithms to investigate pan-genomes efficiently.

RESULTS: This work focuses on providing a tool for discovering and visualizing the relationships between the sequences constituting a pan-genome. A new structure to represent such relationships - called affinity tree - is proposed. Each node of this tree has assigned a subset of genomes, as well as their homogeneity level and averaged consensus sequence. Moreover, subsets assigned to sibling nodes form a partition of the genomes assigned to their parent.

CONCLUSIONS: Functionality of affinity tree is demonstrated on simulated data and on the Ebola virus pan-genome. Furthermore, two software packages are provided: PangTreeBuild constructs affinity tree, while PangTreeVis presents its result.

RevDate: 2020-04-16

Yu Y, C Wei (2020)

A powerful HUPAN on a pan-genome study: significance and perspectives.

Cancer biology & medicine, 17(1):1-5.

RevDate: 2020-04-15

Moulana A, Anderson RE, Fortunato CS, et al (2020)

Selection Is a Significant Driver of Gene Gain and Loss in the Pangenome of the Bacterial Genus Sulfurovum in Geographically Distinct Deep-Sea Hydrothermal Vents.

mSystems, 5(2): pii:5/2/e00673-19.

Microbial genomes have highly variable gene content, and the evolutionary history of microbial populations is shaped by gene gain and loss mediated by horizontal gene transfer and selection. To evaluate the influence of selection on gene content variation in hydrothermal vent microbial populations, we examined 22 metagenome-assembled genomes (MAGs) (70 to 97% complete) from the ubiquitous vent Epsilonbacteraeota genus Sulfurovum that were recovered from two deep-sea hydrothermal vent regions, Axial Seamount in the northeastern Pacific Ocean (13 MAGs) and the Mid-Cayman Rise in the Caribbean Sea (9 MAGs). Genes involved in housekeeping functions were highly conserved across Sulfurovum lineages. However, genes involved in environment-specific functions, and in particular phosphate regulation, were found mostly in Sulfurovum genomes from the Mid-Cayman Rise in the low-phosphate Atlantic Ocean environment, suggesting that nutrient limitation is an important selective pressure for these bacteria. Furthermore, genes that were rare within the pangenome were more likely to undergo positive selection than genes that were highly conserved in the pangenome, and they also appeared to have experienced gene-specific sweeps. Our results suggest that selection is a significant driver of gene gain and loss for dominant microbial lineages in hydrothermal vents and highlight the importance of factors like nutrient limitation in driving microbial adaptation and evolution.IMPORTANCE Microbes can alter their gene content through the gain and loss of genes. However, there is some debate as to whether natural selection or neutral processes play a stronger role in molding the gene content of microbial genomes. In this study, we examined variation in gene content for the Epsilonbacteraeota genus Sulfurovum from deep-sea hydrothermal vents, which are dynamic habitats known for extensive horizontal gene transfer within microbial populations. Our results show that natural selection is a strong driver of Sulfurovum gene content and that nutrient limitation in particular has shaped the Sulfurovum genome, leading to differences in gene content between ocean basins. Our results also suggest that recently acquired genes undergo stronger selection than genes that were acquired in the more distant past. Overall, our results highlight the importance of natural selection in driving the evolution of microbial populations in these dynamic habitats.

RevDate: 2020-04-12

Oh YJ, Kim JY, Jo HE, et al (2020)

Lentibacillus cibarius sp. nov., isolated from kimchi, a Korean fermented food.

Journal of microbiology (Seoul, Korea) pii:10.1007/s12275-020-9507-7 [Epub ahead of print].

Two bacterial strains designated NKC220-2T and NKC851-2 were isolated from commercial kimchi from different areas in Korea. The strains were Gram-positive, aerobic, oxidase-and catalase-positive, rod-shaped, spore-forming, non-motile, and halophilic bacteria. Both strains grew without NaCl, unlike type species in the genus Lentibacillus. The optimal pH for growth was 8.0, higher than that of the type species in the genus Lentibacillus, although growth was observed at pH 5.5-9.0. 16S rRNA gene sequence-based phylogenetic analysis indicated that the two strains (99.3-99.9% similarity) are grouped within the genus Lentibacillus and most closely related to Lentibacillus juripiscarius IS40-3T (97.4-97.6% similarity) isolated from fish sauce in Thailand. OrthoANI value between two novel strains and Lentibacillus lipolyticus SSKP1-9T (79.5-79.6% similarity) was far lower than the species demarcation threshold. Comparative genomic analysis displayed differences between the two strains as well as among other strains belonging to Lentibacillus. Furthermore, each isolate had strain-specific groups of orthologous genes based on pangenome analysis. Genomic G + C contents of strains NKC-220-2T and NKC851-2 were 41.9 and 42.2 mol%, respectively. The strains contained meso-diaminopimelic acid in their cell walls, and the major menaquinone was menaquinone-7. Phosphatidylglycerol, diphosphatidylglycerol, and an unidentified glycolipid, aminophospholipid, and phospholipid were the major polar lipid components of both strains. The major cellular fatty acids of the strains were anteiso-C15:0 and an-teiso-C17:0. Based on phenotypic, genomic, phylogenetic, and chemotaxonomic features, strains NKC220-2T and NKC851-2 represent novel species of the genus Lentibacillus, for which the name Lentibacillus cibarius sp. nov. is proposed. The type strain is NKC220-2T (= KACC 21232T = JCM 33390T).

RevDate: 2020-04-11

Zeb S, Gulfam SM, H Bokhari (2020)

Comparative core/pan genome analysis of Vibrio cholerae isolates from Pakistan.

Infection, genetics and evolution : journal of molecular epidemiology and evolutionary genetics in infectious diseases pii:S1567-1348(20)30147-7 [Epub ahead of print].

Cholera is an endemic disease in many regions of Asia including, Pakistan. Vibrio cholerae, the causative agent of cholera, is considered as one of the best adapted bacteria due to its ability to withstand severe environmental stresses. The V. cholerae genome is very plastic with many gene additions and deletions. In this study, we sought to understand the diversity of V. cholerae genes in two Pakistani subclades [e.g. Pakistani subclade I (PSC I) and Pakistani subclade II (PSC II)]. We have analyzed 44 PSC I and 56 PSC II strains, respectively. By analyzing our data, it was concluded that subclade group 2 (PSC II) has 2967 core genes repositories, while the PSC 1 group has just 1062 core genes. It was observed that the pangenome in the PSC II group is open while the pan-genome in PSC I are closed. It was also noted that the number of accessory genes (n = 2500) is higher in the PSC I group compared to the PSC II group (n = 550). Furthermore, analysis extended to the study of unique gene profiles suggested that all strains of the PSC II group have unique genes. One strain among the PSC II group had a high number of unique genes (n = 2612). However, in the PSC I group, only a few strains had unique genes with a maximum of 86 unique genes being found in a single strain. Core phylogeny of PSC I indicated that just three groups initially arose from a single common ancestor. At the same time, a complex pattern of evolution was found in the PSC II phylogenetic tree based on core gene information. This comparative genomic analysis has revealed 'waves' of V. cholerae evolution and information on its transmission and ability to modify its genetic content to survive in different environmental conditions. Here, we have investigated how the versatility of V. cholerae, a bacterium that persists across different habitats, is reflected in its genome. The data generated during the study should be extremely beneficial in defining the evolutionary relationship as well as diversity between V. cholerae subclades. It will also benefit epidemiological studies and the design of better treatment strategies for controlling epidemics.

RevDate: 2020-04-11

Zhao J, Liu C, Liu Y, et al (2020)

Genomic characteristics of clinical important ST11 Klebsiella pneumoniae worldwide.

Journal of global antimicrobial resistance pii:S2213-7165(20)30087-4 [Epub ahead of print].

BACKGROUND: ST11 Klebsiella pneumoniae is among the most important clinical pathogen in China, and KL47 and KL64 are the dominant K-types of these strains. Understanding the genomic characteristics of these strains would be critical to their anti-infection treatment.

METHODS: 364 genome sequences of ST11 K. pneumoniae strains isolated from 13 countries from 2003 to 2018 were collected. These genome sequences included 338 downloaded from NCBI database and 26 newly sequenced. Phylogenic analysis, pan-genome and unique genes, resistance and virulence genes analysis were conducted to elucidate the molecular characteristics of these strains.

RESULTS: A total of 19,732 genes were identified from the 364 ST11 strains, and the pan-genome was open, indicating the genetic diversity of ST11 K. pneumoniae. These strains were clustered into 3 clades. Clade 1 contained the most various K-types (14/15, 93.3%) and unique genes. KL47 and KL64 were the dominant K-types of clade 2 and clade 3, accounting for 100% and 99.4% of strains in each clade. KL64 strains contained the most virulence genes, including iucA and rmpA, and the two genes tend to coexist. In addition, strains in clade 1 were isolated from all 13 countries, and the strains in clade 2 and 3 mainly from China.

CONCLUSION: ST11 K. pneumoniae strains of KL64 was becoming a newly emerged superbug with more resistance and virulence genes in China, which was significant different from other countries, and we should be alert the dissemination of this subclone.

RevDate: 2020-04-08

Zhou Y, Chebotarov D, Kudrna D, et al (2020)

A platinum standard pan-genome resource that represents the population structure of Asian rice.

Scientific data, 7(1):113 pii:10.1038/s41597-020-0438-2.

As the human population grows from 7.8 billion to 10 billion over the next 30 years, breeders must do everything possible to create crops that are highly productive and nutritious, while simultaneously having less of an environmental footprint. Rice will play a critical role in meeting this demand and thus, knowledge of the full repertoire of genetic diversity that exists in germplasm banks across the globe is required. To meet this demand, we describe the generation, validation and preliminary analyses of transposable element and long-range structural variation content of 12 near-gap-free reference genome sequences (RefSeqs) from representatives of 12 of 15 subpopulations of cultivated Asian rice. When combined with 4 existing RefSeqs, that represent the 3 remaining rice subpopulations and the largest admixed population, this collection of 16 Platinum Standard RefSeqs (PSRefSeq) can be used as a template to map resequencing data to detect virtually all standing natural variation that exists in the pan-genome of cultivated Asian rice.

RevDate: 2020-04-04

Smith EA, Miller EA, Weber BP, et al (2020)

Genomic landscape of Ornithobacterium rhinotracheale in commercial turkey production in the United States.

Applied and environmental microbiology pii:AEM.02874-19 [Epub ahead of print].

Ornithobacterium rhinotracheale (ORT) is a causative agent of respiratory tract infections in avian hosts worldwide, but is a particular problem for commercial turkey production. Little is known about the ecologic and evolutionary dynamics of ORT, which makes prevention and control of this pathogen a challenge. The purpose of this study was to gain insight into the genetic relationships between ORT populations through comparative genomics of clinical isolates from different US turkey producers. ORT clinical isolates were collected from four major US turkey producers and several independent turkey growers from the upper Midwest and Southeast, and whole-genome sequencing was performed. Genomes were compared phylogenetically using single nucleotide polymorphism (SNP)-based analysis, and then assemblies and annotations were performed to identify genes encoding putative virulence factors and antimicrobial resistance determinants. A pangenome approach was also used to establish a core set of genes consistently present in ORT, and to highlight differences in gene content between phylogenetic clades. A total of 1,457 non-recombinant SNPs were identified from 157 ORT genomes, and four distinct phylogenetic clades were identified. Isolates clustered by company on the phylogenetic tree, however, each company had isolates in multiple clades with similar collection dates, indicating that there are multiple ORT strains circulating within each of the companies examined. Additionally, several antimicrobial resistance proteins, putative virulence factors, and the pOR1 plasmid were associated with particular clades and multi-locus sequence types, which may explain why the same strains seem to have persisted in the same turkey operations for decades.Importance The whole-genome approach enhances our understanding of evolutionary relationships between clinical ORT isolates from different commercial turkey producers, and allows for identification of genes associated with virulence, antimicrobial resistance, or mobile genetic elements that are often excluded using traditional typing methods. Additionally, differentiating ORT isolates at the whole-genome level may provide insight into selection of the most appropriate autogenous vaccine strain, or groups of strains, for a given population of clinical isolates.

RevDate: 2020-04-02

Zhu L, Zhao M, Chen M, et al (2020)

The bHLH gene family and its response to saline stress in Jilin ginseng, Panax ginseng C.A. Meyer.

Molecular genetics and genomics : MGG pii:10.1007/s00438-020-01658-w [Epub ahead of print].

Basic helix-loop-helix (bHLH) gene family is a gene family of transcription factors that plays essential roles in plant growth and development, secondary metabolism and response to biotic and abiotic stresses. Therefore, a comprehensive knowledge of the bHLH gene family is paramount to understand the molecular mechanisms underlying these processes and develop advanced technologies to manipulate the processes efficiently. Ginseng, Panax ginseng C.A. Meyer, is a well-known medicinal herb; however, little is known about the bHLH genes (PgbHLH) in the species. Here, we identified 137 PgbHLH genes from Jilin ginseng cultivar, Damaya, widely cultivated in Jilin, China, of which 50 are newly identified by pan-genome analysis. These 137 PgbHLH genes were phylogenetically classified into 26 subfamilies, suggesting their sequence diversification. They are alternatively spliced into 366 transcripts in a 4-year-old plant and involved in 11 functional subcategories of the gene ontology, indicating their functional differentiation in ginseng. The expressions of the PgbHLH genes dramatically vary spatio-temporally and across 42 genotypes, but they are still somehow functionally correlated. Moreover, the PgbHLH gene family, at least some of its genes, is shown to have roles in plant response to the abiotic stress of saline. These results provide a new insight into the evolution and functional differentiation of the bHLH gene family in plants, new bHLH genes to the PgbHLH gene family, and saline stress-responsive genes for genetic improvement in ginseng and other plant species.

RevDate: 2020-04-01

Niu XK, Narsing Rao MP, Dong ZY, et al (2020)

Vulcaniibacterium gelatinicum sp. nov., a moderately thermophilic bacterium isolated from a hot spring.

International journal of systematic and evolutionary microbiology, 70(3):1571-1577.

The present study aimed to determine the taxonomic positions of strains designated R-5-52-3T, R-5-33-5-1-2, R-5-48-2 and R-5-51-4 isolated from hot spring water samples. Cells of these strains were Gram-stain-negative, non-motile and rod-shaped. The strains shared highest 16S rRNA gene sequence similarity with Vulcaniibacterium thermophilum KCTC 32020T (95.1%). Growth occurred at 28-55 °C, at pH 6-8 and with up to 3 % (w/v) NaCl. DNA fingerprinting, biochemical, phylogenetic and 16S rRNA gene sequence analyses suggested that R-5-52-3T, R-5-33-5-1-2, R-5-48-2 and R-5-51-4 were different strains but belonged to the same species. Hence, R-5-52-3T was chosen for further analysis and R-5-33-5-1-2, R-5-48-2 and R-5-51-4 were considered as additional strains of this species. R-5-52-3T possessed Q-8 as the only quinone and iso-C15:0, iso-C11:0, C16 : 0 and iso-C17 : 0 as major fatty acids. The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, unidentified polar lipids and two unidentified phospholipids. The genomic G+C content was 71.6 mol%. Heat shock proteins (e.g. Hsp20, GroEL, DnaK and Clp ATPases) were noted in the R-5-52-3T genome, which could suggest its protection in the hot spring environment. Pan-genome analysis showed the number of singleton gene clusters among Vulcaniibacterium members varied. Average nucleotide identity (ANI) values between R-5-52-3T, Vulcaniibacterium tengchongense YIM 77520T and V. thermophilum KCTC 32020T were 80.1-85.8 %, which were below the cut-off level (95-96 %) recommended as the ANI criterion for interspecies identity. Thus, based on the above results, strain R-5-52-3T represents a novel species of the genus Vulcaniibacterium, for which the name Vulcaniibacterium gelatinicum sp. nov. is proposed. The type strain is R-5-52-3T (=KCTC 72061T=CGMCC 1.16678T).

RevDate: 2020-03-21

Dunning LT, PA Christin (2020)

Reticulate evolution, lateral gene transfer, and innovation in plants.

American journal of botany [Epub ahead of print].

RevDate: 2020-03-20

Muthukumarasamy U, Preusse M, Kordes A, et al (2020)

Single-nucleotide polymorphism-based genetic diversity analysis of clinical Pseudomonas aeruginosa isolates.

Genome biology and evolution pii:5810496 [Epub ahead of print].

Extensive use of next-generation sequencing has the potential to transform our knowledge on how genomic variation within bacterial species impacts phenotypic versatility. Since different environments have unique selection pressures, they drive divergent evolution. However, there is also parallel or convergent evolution of traits in independent bacterial isolates inhabiting similar environments. The application of tools to describe population-wide genomic diversity provides an opportunity to measure the predictability of genetic changes underlying adaptation. Here we describe patterns of sequence variations in the core genome among 99 individual Pseudomonas aeruginosa clinical isolates and identified single nucleotide polymorphisms (SNPs) that are the basis for branching of the phylogenetic tree. We also identified SNPs that were acquired independently, in separate lineages, and not through inheritance from a common ancestor. While our results demonstrate that the P. aeruginosa core genome is highly conserved and in general, not subject to adaptive evolution, instances of parallel evolution will provide an opportunity to uncover genetic changes that underlie phenotypic diversity.

RevDate: 2020-03-19

Gautreau G, Bazin A, Gachet M, et al (2020)

PPanGGOLiN: Depicting microbial diversity via a partitioned pangenome graph.

PLoS computational biology, 16(3):e1007732 pii:PCOMPBIOL-D-19-02015 [Epub ahead of print].

The use of comparative genomics for functional, evolutionary, and epidemiological studies requires methods to classify gene families in terms of occurrence in a given species. These methods usually lack multivariate statistical models to infer the partitions and the optimal number of classes and don't account for genome organization. We introduce a graph structure to model pangenomes in which nodes represent gene families and edges represent genomic neighborhood. Our method, named PPanGGOLiN, partitions nodes using an Expectation-Maximization algorithm based on multivariate Bernoulli Mixture Model coupled with a Markov Random Field. This approach takes into account the topology of the graph and the presence/absence of genes in pangenomes to classify gene families into persistent, cloud, and one or several shell partitions. By analyzing the partitioned pangenome graphs of isolate genomes from 439 species and metagenome-assembled genomes from 78 species, we demonstrate that our method is effective in estimating the persistent genome. Interestingly, it shows that the shell genome is a key element to understand genome dynamics, presumably because it reflects how genes present at intermediate frequencies drive adaptation of species, and its proportion in genomes is independent of genome size. The graph-based approach proposed by PPanGGOLiN is useful to depict the overall genomic diversity of thousands of strains in a compact structure and provides an effective basis for very large scale comparative genomics. The software is freely available at

RevDate: 2020-03-19

Hasni I, Andréani J, Colson P, et al (2020)

Description of Virulent Factors and Horizontal Gene Transfers of Keratitis-Associated Amoeba Acanthamoeba Triangularis by Genome Analysis.

Pathogens (Basel, Switzerland), 9(3): pii:pathogens9030217.

Acanthamoeba triangularis strain SH 621 is a free-living amoeba belonging to Acanthamoeba ribo-genotype T4. This ubiquitous protist is among the free-living amoebas responsible for Acanthamoeba keratitis, a severe infection of human cornea. Genome sequencing and genomic comparison were carried out to explore the biological functions and to better understand the virulence mechanism related to the pathogenicity of Acanthamoeba keratitis. The genome assembly harbored a length of 66.43 Mb encompassing 13,849 scaffolds. The analysis of predicted proteins reported the presence of 37,062 ORFs. A complete annotation revealed 33,168 and 16,605 genes that matched with NCBI non-redundant protein sequence (nr) and Cluster of Orthologous Group of proteins (COG) databases, respectively. The Kyoto Encyclopedia of Genes and Genomes Pathway (KEGG) annotation reported a great number of genes related to carbohydrate, amino acid and lipid metabolic pathways. The pangenome performed with 8 available amoeba genomes belonging to genus Acanthamoeba revealed a core genome containing 843 clusters of orthologous genes with a ratio core genome/pangenome of less than 0.02. We detected 48 genes related to virulent factors of Acanthamoeba keratitis. Best hit analyses in nr database identified 99 homologous genes shared with amoeba-resisting microorganisms. This study allows the deciphering the genome of a free-living amoeba with medical interest and provides genomic data to better understand virulence-related Acanthamoeba keratitis.

RevDate: 2020-03-19

Kim YJ, Park JY, Balusamy SR, et al (2020)

Comprehensive Genome Analysis on the Novel Species Sphingomonas panacis DCY99T Reveals Insights into Iron Tolerance of Ginseng.

International journal of molecular sciences, 21(6): pii:ijms21062019.

Plant growth-promoting rhizobacteria play vital roles not only in plant growth, but also in reducing biotic/abiotic stress. Sphingomonas panacis DCY99T is isolated from soil and root of Panax ginseng with rusty root disease, characterized by raised reddish-brown root and this is seriously affects ginseng cultivation. To investigate the relationship between 159 sequenced Sphingomonas strains, pan-genome analysis was carried out, which suggested genomic diversity of the Sphingomonas genus. Comparative analysis of S. panacis DCY99T with Sphingomonas sp. LK11 revealed plant growth-promoting potential of S. panacis DCY99T through indole acetic acid production, phosphate solubilizing, and antifungal abilities. Detailed genomic analysis has shown that S. panacis DCY99T contain various heavy metals resistance genes in its genome and the plasmid. Functional analysis with Sphingomonas paucimobilis EPA505 predicted that S. panacis DCY99T possess genes for degradation of polyaromatic hydrocarbon and phenolic compounds in rusty-ginseng root. Interestingly, when primed ginseng with S. panacis DCY99T during high concentration of iron exposure, iron stress of ginseng was suppressed. In order to detect S. panacis DCY99T in soil, biomarker was designed using spt gene. This study brings new insights into the role of S. panacis DCY99T as a microbial inoculant to protect ginseng plants against rusty root disease.

RevDate: 2020-03-18

Kang SM, Asaf S, Khan AL, et al (2020)

Complete Genome Sequence of Pseudomonas psychrotolerans CS51, a Plant Growth-Promoting Bacterium, Under Heavy Metal Stress Conditions.

Microorganisms, 8(3): pii:microorganisms8030382.

In the current study, we aimed to elucidate the plant growth-promoting characteristics of Pseudomonas psychrotolerans CS51 under heavy metal stress conditions (Zn, Cu, and Cd) and determine the genetic makeup of the CS51 genome using the single-molecule real-time (SMRT) sequencing technology of Pacific Biosciences. The results revealed that inoculation with CS51 induced endogenous indole-3-acetic acid (IAA) and gibberellins (GAs), which significantly enhanced cucumber growth (root shoot length) and increased the heavy metal tolerance of cucumber plants. Moreover, genomic analysis revealed that the CS51 genome consisted of a circular chromosome of 5,364,174 base pairs with an average G+C content of 64.71%. There were around 4774 predicted protein-coding sequences (CDSs) in 4859 genes, 15 rRNA genes, and 67 tRNA genes. Around 3950 protein-coding genes with function prediction and 733 genes without function prediction were identified. Furthermore, functional analyses predicted that the CS51 genome could encode genes required for auxin biosynthesis, nitrate and nitrite ammonification, the phosphate-specific transport system, and the sulfate transport system, which are beneficial for plant growth promotion. The heavy metal resistance of CS51 was confirmed by the presence of genes responsible for cobalt-zinc-cadmium resistance, nickel transport, and copper homeostasis in the CS51 genome. The extrapolation of the curve showed that the core genome contained a minimum of 2122 genes (95% confidence interval = 2034.24 to 2080.215). Our findings indicated that the genome sequence of CS51 may be used as an eco-friendly bioresource to promote plant growth in heavy metal-contaminated areas.

RevDate: 2020-03-14

Satyam R, Bhardwaj T, Jha NK, et al (2020)

Toward a chimeric vaccine against multiple isolates of Mycobacteroides - An integrative approach.

Life sciences pii:S0024-3205(20)30289-7 [Epub ahead of print].

AIM: Nontuberculous mycobacterial infection (NTM) such as endophthalmitis, dacryocystitis, and canaliculitis are pervasive across the globe and are currently managed by antibiotics. However, the recent cases of Mycobacteroides developing drug resistance reported along with the improper practice of medicine intrigued us to explore its genomic and proteomic canvas at a global scale and develop a chimeric vaccine against Mycobacteroides.

MAIN METHODS: We carried out a vivid genomic study on five recently sequenced strains of Mycobacteroides and explored their Pan-Core genome/proteome in three different Phases. The promiscuous antigenic proteins were identified via a subtractive proteomics approach that qualified for virulence causation, resistance and essentiality factors for this notorious bacterium. An integrated pipeline was developed for the identification of B-Cell, MHC (Major histocompatibility complex) class I and II epitopes.

KEY FINDINGS: Phase I identified the shreds of evidence of reductive evolution and propensity of the Pan-genome of Mycobacteroides getting closed soon. Phase II and Phase III produced 8 vaccine constructs. Our final vaccine construct, V6 qualified for all tests such as absence for allergenicity, presence of antigenicity, etc. V6 contains β defensin as an adjuvant, linkers, LAMP1 (Lysosomal-associated membrane protein 1) signal peptide, and PADRE (Pan HLA-DR epitopes) amino acid sequence. Besides, V6 also interacts with a maximum number of MHC molecules and the TLR4/MD2 (Toll-like Receptor 4/Myeloid Differentiation Factor 2) complex confirmed by docking and molecular dynamics simulation studies.

SIGNIFICANCE: The knowledge harnessed from the current study can help improve the current treatment regimens or in an event of an outbreak and propel further related studies.

RevDate: 2020-03-10

Chen M, Xu CY, Wang X, et al (2020)

Comparative genomics analysis of c-di-GMP metabolism and regulation in Microcystis aeruginosa.

BMC genomics, 21(1):217 pii:10.1186/s12864-020-6591-3.

BACKGROUND: Cyanobacteria are of special concern because they proliferate in eutrophic water bodies worldwide and affect water quality. As an ancient photosynthetic microorganism, cyanobacteria can survive in ecologically diverse habitats because of their capacity to rapidly respond to environmental changes through a web of complex signaling networks, including using second messengers to regulate physiology or metabolism. A ubiquitous second messenger, bis-(3',5')-cyclic-dimeric-guanosine monophosphate (c-di-GMP), has been found to regulate essential behaviors in a few cyanobacteria but not Microcystis, which are the most dominant species in cyanobacterial blooms. In this study, comparative genomics analysis was performed to explore the genomic basis of c-di-GMP signaling in Microcystis aeruginosa.

RESULTS: Proteins involved in c-di-GMP metabolism and regulation, such as diguanylate cyclases, phosphodiesterases, and PilZ-containing proteins, were encoded in M. aeruginosa genomes. However, the number of identified protein domains involved in c-di-GMP signaling was not proportional to the size of M. aeruginosa genomes (4.97 Mb in average). Pan-genome analysis showed that genes involved in c-di-GMP metabolism and regulation are conservative in M. aeruginosa strains. Phylogenetic analysis showed good congruence between the two types of phylogenetic trees based on 31 highly conserved protein-coding genes and sensor domain-coding genes. Propensity for gene loss analysis revealed that most of genes involved in c-di-GMP signaling are stable in M. aeruginosa strains. Moreover, bioinformatics and structure analysis of c-di-GMP signal-related GGDEF and EAL domains revealed that they all possess essential conserved amino acid residues that bind the substrate. In addition, it was also found that all selected M. aeruginosa genomes encode PilZ domain containing proteins.

CONCLUSIONS: Comparative genomics analysis of c-di-GMP metabolism and regulation in M. aeruginosa strains helped elucidating the genetic basis of c-di-GMP signaling pathways in M. aeruginosa. Knowledge of c-di-GMP metabolism and relevant signal regulatory processes in cyanobacteria can enhance our understanding of their adaptability to various environments and bloom-forming mechanism.

RevDate: 2020-03-09

Aaltonen K, Kant R, Eklund M, et al (2020)

Streptococcus halichoeri: Comparative Genomics of an Emerging Pathogen.

International journal of genomics, 2020:8708305.

Streptococcus halichoeri is an emerging pathogen with a variety of host species and zoonotic potential. It has been isolated from grey seals and other marine mammals as well as from human infections. Beginning in 2010, two concurrent epidemics were identified in Finland, in fur animals and domestic dogs, respectively. The fur animals suffered from a new disease fur animal epidemic necrotic pyoderma (FENP) and the dogs presented with ear infections with poor treatment response. S. halichoeri was isolated in both studies, albeit among other pathogens, indicating a possible role in the disease etiologies. The aim was to find a possible common origin of the fur animal and dog isolates and study the virulence factors to assess pathogenic potential. Isolates from seal, human, dogs, and fur animals were obtained for comparison. The whole genomes were sequenced from 20 different strains using the Illumina MiSeq platform and annotated using an automatic annotation pipeline RAST. The core and pangenomes were formed by comparing the genomes against each other in an all-against-all comparison. A phylogenetic tree was constructed using the genes of the core genome. Virulence factors were assessed using the Virulence Factor Database (VFDB) concentrating on the previously confirmed streptococcal factors. A core genome was formed which encompassed approximately half of the genes in Streptococcus halichoeri. The resulting core was nearly saturated and would not change significantly by adding more genomes. The remaining genes formed the pangenome which was highly variable and would still evolve after additional genomes. The results highlight the great adaptability of this bacterium possibly explaining the ease at which it switches hosts and environments. Virulence factors were also analyzed and were found primarily in the core genome. They represented many classes and functions, but the largest single category was adhesins which again supports the marine origin of this species.

RevDate: 2020-03-06

Moustafa AM, PJ Planet (2020)

WhatsGNU: a tool for identifying proteomic novelty.

Genome biology, 21(1):58 pii:10.1186/s13059-020-01965-w.

To understand diversity in enormous collections of genome sequences, we need computationally scalable tools that can quickly contextualize individual genomes based on their similarities and identify features of each genome that make them unique. We present WhatsGNU, a tool based on exact match proteomic compression that, in seconds, classifies any new genome and provides a detailed report of protein alleles that may have novel functional differences. We use this technique to characterize the total allelic diversity (panallelome) of Salmonella enterica, Mycobacterium tuberculosis, Pseudomonas aeruginosa, and Staphylococcus aureus. It could be extended to others. WhatsGNU is available from

RevDate: 2020-03-05

Seif Y, Choudhary KS, Hefner Y, et al (2020)

Metabolic and genetic basis for auxotrophies in Gram-negative species.

Proceedings of the National Academy of Sciences of the United States of America pii:1910499117 [Epub ahead of print].

Auxotrophies constrain the interactions of bacteria with their environment, but are often difficult to identify. Here, we develop an algorithm (AuxoFind) using genome-scale metabolic reconstruction to predict auxotrophies and apply it to a series of available genome sequences of over 1,300 Gram-negative strains. We identify 54 auxotrophs, along with the corresponding metabolic and genetic basis, using a pangenome approach, and highlight auxotrophies conferring a fitness advantage in vivo. We show that the metabolic basis of auxotrophy is species-dependent and varies with 1) pathway structure, 2) enzyme promiscuity, and 3) network redundancy. Various levels of complexity constitute the genetic basis, including 1) deleterious single-nucleotide polymorphisms (SNPs), in-frame indels, and deletions; 2) single/multigene deletion; and 3) movement of mobile genetic elements (including prophages) combined with genomic rearrangements. Fourteen out of 19 predictions agree with experimental evidence, with the remaining cases highlighting shortcomings of sequencing, assembly, annotation, and reconstruction that prevent predictions of auxotrophies. We thus develop a framework to identify the metabolic and genetic basis for auxotrophies in Gram-negatives.

RevDate: 2020-03-05

Jin Y, Zhou J, Zhou J, et al (2020)

Genome-based classification of Burkholderia cepacia complex provides new insight into its taxonomic status.

Biology direct, 15(1):6 pii:10.1186/s13062-020-0258-5.

BACKGROUND: Accurate classification of different Burkholderia cepacia complex (BCC) species is essential for therapy, prognosis assessment and research. The taxonomic status of BCC remains problematic and an improved knowledge about the classification of BCC is in particular needed.

METHODS: We compared phylogenetic trees of BCC based on 16S rRNA, recA, hisA and MLSA (multilocus sequence analysis). Using the available whole genome sequences of BCC, we inferred a species tree based on estimated single-copy orthologous genes and demarcated species of BCC using dDDH/ANI clustering.

RESULTS: We showed that 16S rRNA, recA, hisA and MLSA have limited resolutions in the taxonomic study of closely related bacteria such as BCC. Our estimated species tree and dDDH/ANI clustering clearly separated 116 BCC strains into 36 clusters. With the appropriate reclassification of misidentified strains, these clusters corresponded to 22 known species as well as 14 putative novel species.

CONCLUSIONS: This is the first large-scale and systematic study of the taxonomic status of the BCC and could contribute to further insights into BCC taxonomy. Our study suggested that conjunctive use of core phylogeny based on single-copy orthologous genes, as well as pangenome-based dDDH/ANI clustering would provide a preferable framework for demarcating closely related species.

REVIEWER: This article was reviewed by Dr. Xianwen Ren.

RevDate: 2020-03-04

Thukral A, Ross K, Hansen C, et al (2020)

A single dose polyanhydride-based nanovaccine against paratuberculosis infection.

NPJ vaccines, 5:15 pii:164.

Mycobacterium avium subsp. paratuberculosis (M. paratuberculosis) causes Johne's disease in ruminants and is characterized by chronic gastroenteritis leading to heavy economic losses to the dairy industry worldwide. The currently available vaccine (inactivated bacterin in oil base) is not effective in preventing pathogen shedding and is rarely used to control Johne's disease in dairy herds. To develop a better vaccine that can prevent the spread of Johne's disease, we utilized polyanhydride nanoparticles (PAN) to encapsulate mycobacterial antigens composed of whole cell lysate (PAN-Lysate) and culture filtrate (PAN-Cf) of M. paratuberculosis. These nanoparticle-based vaccines (i.e., nanovaccines) were well tolerated in mice causing no inflammatory lesions at the site of injection. Immunological assays demonstrated a substantial increase in the levels of antigen-specific T cell responses post-vaccination in the PAN-Cf vaccinated group as indicated by high percentages of triple cytokine (IFN-γ, IL-2, TNF-α) producing CD8+ T cells. Following challenge, animals vaccinated with PAN-Cf continued to produce significant levels of double (IFN-γ, TNF-α) and single cytokine (IFN-γ) secreting CD8+ T cells compared with animals vaccinated with an inactivated vaccine. A significant reduction in bacterial load was observed in multiple organs of animals vaccinated with PAN-Cf, which is a clear indication of protection. Overall, the use of polyanhydride nanovaccines resulted in development of protective and sustained immunity against Johne's disease, an approach that could be applied to counter other intracellular pathogens.

RevDate: 2020-02-28

Tekedar HC, Blom J, Kalindamar S, et al (2020)

Comparative genomics of the fish pathogens Edwardsiella ictaluri 93-146 and Edwardsiella piscicida C07-087.

Microbial genomics, 6(2):.

Edwardsiella ictaluri and Edwardsiella piscicida are important fish pathogens affecting cultured and wild fish worldwide. To investigate the genome-level differences and similarities between catfish-adapted strains in these two species, the complete E. ictaluri 93-146 and E. piscicida C07-087 genomes were evaluated by applying comparative genomics analysis. All available complete (10) and non-complete (19) genomes from five Edwardsiella species were also included in a systematic analysis. Average nucleotide identity and core-genome phylogenetic tree analyses indicated that the five Edwardsiella species were separated from each other. Pan-/core-genome analyses for the 29 strains from the five species showed that genus Edwardsiella members have 9474 genes in their pan genome, while the core genome consists of 1421 genes. Orthology cluster analysis showed that E. ictaluri and E. piscicida genomes have the greatest number of shared clusters. However, E. ictaluri and E. piscicida also have unique features; for example, the E. ictaluri genome encodes urease enzymes and cytochrome o ubiquinol oxidase subunits, whereas E. piscicida genomes encode tetrathionate reductase operons, capsular polysaccharide synthesis enzymes and vibrioferrin-related genes. Additionally, we report for what is believed to be the first time that E. ictaluri 93-146 and three other E. ictaluri genomes encode a type IV secretion system (T4SS), whereas none of the E. piscicida genomes encode this system. Additionally, the E. piscicida C07-087 genome encodes two different type VI secretion systems. E. ictaluri genomes tend to encode more insertion elements, phage regions and genomic islands than E. piscicida. We speculate that the T4SS could contribute to the increased number of mobilome elements in E. ictaluri compared to E. piscicida. Two of the E. piscicida genomes encode full CRISPR-Cas regions, whereas none of the E. ictaluri genomes encode Cas proteins. Overall, comparison of the E. ictaluri and E. piscicida genomes reveals unique features and provides new insights on pathogenicity that may reflect the host adaptation of the two species.

RevDate: 2020-02-28

Li Q, Cooper RE, Wegner CE, et al (2020)

Molecular Mechanisms Underpinning Aggregation in Acidiphilium sp. C61 Isolated from Iron-Rich Pelagic Aggregates.

Microorganisms, 8(3): pii:microorganisms8030314.

Iron-rich pelagic aggregates (iron snow) are hot spots for microbial interactions. Using iron snow isolates, we previously demonstrated that the iron-oxidizer Acidithrix sp. C25 triggers Acidiphilium sp. C61 aggregation by producing the infochemical 2-phenethylamine (PEA). Here, we showed slightly enhanced aggregate formation in the presence of PEA on different Acidiphilium spp. but not other iron-snow microorganisms, including Acidocella sp. C78 and Ferrovum sp. PN-J47. Next, we sequenced the Acidiphilium sp. C61 genome to reconstruct its metabolic potential. Pangenome analyses of Acidiphilium spp. genomes revealed the core genome contained 65 gene clusters associated with aggregation, including autoaggregation, motility, and biofilm formation. Screening the Acidiphilium sp. C61 genome revealed the presence of autotransporter, flagellar, and extracellular polymeric substances (EPS) production genes. RNA-seq analyses of Acidiphilium sp. C61 incubations (+/- 10 µM PEA) indicated genes involved in energy production, respiration, and genetic processing were the most upregulated differentially expressed genes in the presence of PEA. Additionally, genes involved in flagellar basal body synthesis were highly upregulated, whereas the expression pattern of biofilm formation-related genes was inconclusive. Our data shows aggregation is a common trait among Acidiphilium spp. and PEA stimulates the central cellular metabolism, potentially advantageous in aggregates rapidly falling through the water column.

RevDate: 2020-02-27

González-Castillo A, Enciso-Ibarra J, B Gomez-Gil (2020)

Genomic taxonomy of the Mediterranei clade of the genus Vibrio (Gammaproteobacteria).

Antonie van Leeuwenhoek pii:10.1007/s10482-020-01396-4 [Epub ahead of print].

The first genomic study of Mediterranei clade using five type strains (V. mediterranei, V. maritimus, V. variabilis, V. thalassae, and V. barjaei) and fourteen reference strains isolated from marine organisms, seawater, water and sediments of the sea was performed. These bacterial strains were characterised by means of a polyphasic approach comprising 16S rRNA gene, multilocus sequence analysis (MLSA) of 139 single-copy genes, the DNA G + C content, ANI, and in silico phenotypic characterisation. We found that the species of the Mediterranei clade formed two separate clusters based in 16S rRNA gene sequence similarity, MLSA, OrthoANI, and Codon and Amino Acid usage. The Mediterranei clade species showed values between 76 and 95% for ANIb, 84 and 95% for ANIm. The core genome consisted of 2057 gene families and the pan-genome of 13,094 gene families. Based on the genomic analyses performed, the Mediterranei clade can be divided in two clusters, one with the strains of V. maritimus, V. variabilis and two potential new species, and the other cluster with the strains of V. mediterranei, V. thalassae, and V. barjaei.

RevDate: 2020-02-26

Whelan FJ, Rusilowicz M, JO McInerney (2020)

Coinfinder: detecting significant associations and dissociations in pangenomes.

Microbial genomics [Epub ahead of print].

The accessory genes of prokaryote and eukaryote pangenomes accumulate by horizontal gene transfer, differential gene loss, and the effects of selection and drift. We have developed Coinfinder, a software program that assesses whether sets of homologous genes (gene families) in pangenomes associate or dissociate with each other (i.e. are 'coincident') more often than would be expected by chance. Coinfinder employs a user-supplied phylogenetic tree in order to assess the lineage-dependence (i.e. the phylogenetic distribution) of each accessory gene, allowing Coinfinder to focus on coincident gene pairs whose joint presence is not simply because they happened to appear in the same clade, but rather that they tend to appear together more often than expected across the phylogeny. Coinfinder is implemented in C++, Python3 and R and is freely available under the GNU license from

RevDate: 2020-02-22

Khan AMAM, Hauk VJ, Ibrahim M, et al (2020)

Caldicellulosiruptor bescii adheres to polysaccharides using a type IV pilin-dependent mechanism.

Applied and environmental microbiology pii:AEM.00200-20 [Epub ahead of print].

Biological hydrolysis of cellulose above 70°C involves microorganisms that secrete free enzymes, and deploy separate protein systems to adhere to their substrate. Strongly cellulolytic Caldicellulosiruptor bescii is one such extreme thermophile, which deploys modular, multi-functional carbohydrate acting enzymes to deconstruct plant biomass. Additionally, C. bescii also encodes for non-catalytic carbohydrate binding proteins, which likely evolved as a mechanism to compete against other heterotrophs in carbon limited biotopes that these bacteria inhabit. Analysis of the Caldicellulosiruptor pangenome identified a type IV pilus (T4P) locus encoded upstream of the tāpirins, that is encoded for by all Caldicellulosiruptor species. In this study, we sought to determine if the C. bescii T4P plays a role in attachment to plant polysaccharides. The major C. bescii pilin (CbPilA) was identified by the presence of pilin-like protein domains, paired with transcriptomics and proteomics data. Using immuno-dot blots, we determined that the plant polysaccharide, xylan, induced production of CbPilA 10 to 14-fold higher than glucomannan or xylose. Furthermore, we are able to demonstrate that recombinant CbPilA directly interacts with xylan, and cellulose at elevated temperatures. Localization of CbPilA at the cell surface was confirmed by immunofluorescence microscopy. Lastly, a direct role for CbPilA in cell adhesion was demonstrated using recombinant CbPilA or anti-CbPilA antibodies to reduce C. bescii cell adhesion to xylan and crystalline cellulose up to 4.5 and 2-fold, respectively. Based on these observations, we propose that CbPilA and by extension, the T4P, play a role in Caldicellulosiruptor cell attachment to plant biomass.IMPORTANCEMost microorganisms are capable of attaching to surfaces in order to persist in their environment. Type IV (T4) pili produced by select mesophilic Firmicutes promote adherence, however a role for T4 pili encoded by thermophilic members of this phylum has yet to be demonstrated. Prior comparative genomics analyses identified a T4 pilus locus encoded by an extremely thermophilic genus within the Firmicutes. Here, we demonstrate that attachment to plant biomass-related carbohydrates by strongly cellulolytic Caldicellulosiruptor bescii is mediated by T4 pilins. Surprisingly, xylan but not cellulose induced expression of the major T4 pilin. Regardless, the C. bescii T4 pilin interacts with both polysaccharides at high temperatures, and is located to the cell surface where it is directly involved in C. bescii attachment. Adherence to polysaccharides is likely key to survival in environments where carbon sources are limiting, allowing C. bescii to compete against other plant degrading microorganisms.

RevDate: 2020-02-20

Romano I, Ventorino V, O Pepe (2020)

Effectiveness of Plant Beneficial Microbes: Overview of the Methodological Approaches for the Assessment of Root Colonization and Persistence.

Frontiers in plant science, 11:6.

Issues concerning the use of harmful chemical fertilizers and pesticides that have large negative impacts on environmental and human health have generated increasing interest in the use of beneficial microorganisms for the development of sustainable agri-food systems. A successful microbial inoculant has to colonize the root system, establish a positive interaction and persist in the environment in competition with native microorganisms living in the soil through rhizocompetence traits. Currently, several approaches based on culture-dependent, microscopic and molecular methods have been developed to follow bioinoculants in the soil and plant surface over time. Although culture-dependent methods are commonly used to estimate the persistence of bioinoculants, it is difficult to differentiate inoculated organisms from native populations based on morphological characteristics. Therefore, these methods should be used complementary to culture-independent approaches. Microscopy-based techniques (bright-field, electron and fluorescence microscopy) allow to obtain a picture of microbial colonization outside and inside plant tissues also at high resolution, but it is not possible to always distinguish living cells from dead cells by direct observation as well as distinguish bioinoculants from indigenous microbial populations living in soils. In addition, the development of metagenomic techniques, including the use of DNA probes, PCR-based methods, next-generation sequencing, whole-genome sequencing and pangenome methods, provides a complementary approach useful to understand plant-soil-microbe interactions. However, to ensure good results in microbiological analysis, the first fundamental prerequisite is correct soil sampling and sample preparation for the different methodological approaches that will be assayed. Here, we provide an overview of the advantages and limitations of the currently used methods and new methodological approaches that could be developed to assess the presence, plant colonization and soil persistence of bioinoculants in the rhizosphere. We further discuss the possibility of integrating multidisciplinary approaches to examine the variations in microbial communities after inoculation and to track the inoculated microbial strains.

RevDate: 2020-02-19

Yu YY, CC Wei (2020)

[HUPAN promotes striding across of biomedical research from human genome to human pan-genome].

Zhonghua bing li xue za zhi = Chinese journal of pathology, 49(2):105-107.

RevDate: 2020-02-18

Iversen KH, Rasmussen LH, Al-Nakeeb K, et al (2020)

Similar genomic patterns of clinical infective endocarditis and oral isolates of Streptococcus sanguinis and Streptococcus gordonii.

Scientific reports, 10(1):2728 pii:10.1038/s41598-020-59549-4.

Streptococcus gordonii and Streptococcus sanguinis belong to the Mitis group streptococci, which mostly are commensals in the human oral cavity. Though they are oral commensals, they can escape their niche and cause infective endocarditis, a severe infection with high mortality. Several virulence factors important for the development of infective endocarditis have been described in these two species. However, the background for how the commensal bacteria, in some cases, become pathogenic is still not known. To gain a greater understanding of the mechanisms of the pathogenic potential, we performed a comparative analysis of 38 blood culture strains, S. sanguinis (n = 20) and S. gordonii (n = 18) from patients with verified infective endocarditis, along with 21 publicly available oral isolates from healthy individuals, S. sanguinis (n = 12) and S. gordonii (n = 9). Using whole genome sequencing data of the 59 streptococci genomes, functional profiles were constructed, using protein domain predictions based on the translated genes. These functional profiles were used for clustering, phylogenetics and machine learning. A clear separation could be made between the two species. No clear differences between oral isolates and clinical infective endocarditis isolates were found in any of the 675 translated core-genes. Additionally, random forest-based machine learning and clustering of the pan-genome data as well as amino acid variations in the core-genome could not separate the clinical and oral isolates. A total of 151 different virulence genes was identified in the 59 genomes. Among these homologs of genes important for adhesion and evasion of the immune system were found in all of the strains. Based on the functional profiles and virulence gene content of the genomes, we believe that all analysed strains had the ability to become pathogenic.

RevDate: 2020-02-17

Wu H, Wang D, F Gao (2020)

Toward a high-quality pan-genome landscape of Bacillus subtilis by removal of confounding strains.

Briefings in bioinformatics pii:5739184 [Epub ahead of print].

Pan-genome analysis is widely used to study the evolution and genetic diversity of species, particularly in bacteria. However, the impact of strain selection on the outcome of pan-genome analysis is poorly understood. Furthermore, a standard protocol to ensure high-quality pan-genome results is lacking. In this study, we carried out a series of pan-genome analyses of different strain sets of Bacillus subtilis to understand the impact of various strains on the performance and output quality of pan-genome analyses. Consequently, we found that the results obtained by pan-genome analyses of B. subtilis can be influenced by the inclusion of incorrectly classified Bacillus subspecies strains, phylogenetically distinct strains, engineered genome-reduced strains, chimeric strains, strains with a large number of unique genes or a large proportion of pseudogenes, and multiple clonal strains. Since the presence of these confounding strains can seriously affect the quality and true landscape of the pan-genome, we should remove these deviations in the process of pan-genome analyses. Our study provides new insights into the removal of biases from confounding strains in pan-genome analyses at the beginning of data processing, which enables the achievement of a closer representation of a high-quality pan-genome landscape of B. subtilis that better reflects the performance and credibility of the B. subtilis pan-genome. This procedure could be added as an important quality control step in pan-genome analyses for improving the efficiency of analyses, and ultimately contributing to a better understanding of genome function, evolution and genome-reduction strategies for B. subtilis in the future.

RevDate: 2020-02-14

Laflamme B, Dillon MM, Martel A, et al (2020)

The pan-genome effector-triggered immunity landscape of a host-pathogen interaction.

Science (New York, N.Y.), 367(6479):763-768.

Effector-triggered immunity (ETI), induced by host immune receptors in response to microbial effectors, protects plants against virulent pathogens. However, a systematic study of ETI prevalence against species-wide pathogen diversity is lacking. We constructed the Pseudomonas syringae Type III Effector Compendium (PsyTEC) to reduce the pan-genome complexity of 5127 unique effector proteins, distributed among 70 families from 494 strains, to 529 representative alleles. We screened PsyTEC on the model plant Arabidopsis thaliana and identified 59 ETI-eliciting alleles (11.2%) from 19 families (27.1%), with orthologs distributed among 96.8% of P. syringae strains. We also identified two previously undescribed host immune receptors, including CAR1, which recognizes the conserved effectors AvrE and HopAA1, and found that 94.7% of strains harbor alleles predicted to be recognized by either CAR1 or ZAR1.

RevDate: 2020-02-14

Liao F, Mo Z, Gu W, et al (2020)

A comparative genomic analysis between methicillin-resistant Staphylococcus aureus strains of hospital acquired and community infections in Yunnan province of China.

BMC infectious diseases, 20(1):137 pii:10.1186/s12879-020-4866-6.

BACKGROUND: Currently, Staphylococcus aureus is one of the most important pathogens worldwide, especially for methicillin-resistant S. aureus (MRSA) infection. However, few reports referred to patients' MRSA infections in Yunnan province, southwest China.

METHODS: In this study, we selected representative MRSA strains from patients' systemic surveillance in Yunnan province of China, performed the genomic sequencing and compared their features, together with some food derived strains.

RESULTS: Among sixty selective isolates, forty strains were isolated from patients, and twenty isolated from food. Among the patients' strains, sixteen were recognized as community-acquired (CA), compared with 24 for hospital-acquired (HA). ST6-t701, ST59-t437 and ST239-t030 were the three major genotype profiles. ST6-t701 was predominated in food strains, while ST59-t437 and ST239-t030 were the primary clones in patients. The clinical features between CA and HA-MRSA of patients were statistical different. Compared the antibiotic resistant results between patients and food indicated that higher antibiotic resistant rates were found in patients' strains. Totally, the average genome sizes of 60 isolates were 2.79 ± 0.05 Mbp, with GC content 33% and 84.50 ± 0.20% of coding rate. The core genomes of these isolates were 1593 genes. Phylogenetic analysis based on pan-genome and SNP of strains showed that five clustering groups were generated. Clustering ST239-t030 contained all the HA-MRSA cases in this study; clustering ST6-t701 referred to food and CA-MRSA infections in community; clustering ST59-t437 showed the heterogeneity for provoking different clinical diseases in both community and hospital. Phylogenetic tree, incorporating 24 isolates from different regions, indicated ST239-t030 strains in this study were more closely related to T0131 isolate from Tianjin, China, belonged to 'Turkish clade' from Eastern Europe; two groups of ST59-t437 clones of MRSA in Yunnan province were generated, belonged to the 'Asian-Pacific' clone (AP) and 'Taiwan' clone (TW) respectively.

CONCLUSIONS: ST239-t030, ST59-t437 and ST6-t701 were the three major MRSA clones in Yunnan province of China. ST239-t030 clonal Yunnan isolates demonstrated the local endemic of clone establishment for a number of years, whereas ST59-t437 strains revealed the multi-origins of this clone. In general, genomic study on epidemic clones of MRSA in southwest China provided the features and evolution of this pathogen.

RevDate: 2020-02-13

Dos Santos Silva LK, Rodrigues RAL, Dos Santos Pereira Andrade AC, et al (2020)

Isolation and genomic characterization of a new mimivirus of lineage B from a Brazilian river.

Archives of virology pii:10.1007/s00705-020-04542-5 [Epub ahead of print].

Since its discovery, the first identified giant virus associated with amoebae, Acanthamoeba polyphaga mimivirus (APMV), has been rigorously studied to understand the structural and genomic complexity of this virus. In this work, we report the isolation and genomic characterization of a new mimivirus of lineage B, named "Borely moumouvirus". This new virus exhibits a structure and replicative cycle similar to those of other members of the family Mimiviridae. The genome of the new isolate is a linear double-strand DNA molecule of ~1.0 Mb, containing over 900 open reading frames. Genome annotation highlighted different translation system components encoded in the DNA of Borely moumouvirus, including aminoacyl-tRNA synthetases, translation factors, and tRNA molecules, in a distribution similar to that in other lineage B mimiviruses. Pan-genome analysis indicated an increase in the genetic arsenal of this group of viruses, showing that the family Mimiviridae is still expanding. Furthermore, phylogenetic analysis has shown that Borely moumouvirus is closely related to moumouvirus australiensis. This is the first mimivirus lineage B isolated from Brazilian territory to be characterized. Further prospecting studies are necessary for us to better understand the diversity of these viruses so a better classification system can be established.

RevDate: 2020-02-13

Hickey G, Heller D, Monlong J, et al (2020)

Genotyping structural variants in pangenome graphs using the vg toolkit.

Genome biology, 21(1):35 pii:10.1186/s13059-020-1941-7.

Structural variants (SVs) remain challenging to represent and study relative to point mutations despite their demonstrated importance. We show that variation graphs, as implemented in the vg toolkit, provide an effective means for leveraging SV catalogs for short-read SV genotyping experiments. We benchmark vg against state-of-the-art SV genotypers using three sequence-resolved SV catalogs generated by recent long-read sequencing studies. In addition, we use assemblies from 12 yeast strains to show that graphs constructed directly from aligned de novo assemblies improve genotyping compared to graphs built from intermediate SV catalogs in the VCF format.

RevDate: 2020-02-12

Maistrenko OM, Mende DR, Luetge M, et al (2020)

Disentangling the impact of environmental and phylogenetic constraints on prokaryotic within-species diversity.

The ISME journal pii:10.1038/s41396-020-0600-z [Epub ahead of print].

Microbial organisms inhabit virtually all environments and encompass a vast biological diversity. The pangenome concept aims to facilitate an understanding of diversity within defined phylogenetic groups. Hence, pangenomes are increasingly used to characterize the strain diversity of prokaryotic species. To understand the interdependence of pangenome features (such as the number of core and accessory genes) and to study the impact of environmental and phylogenetic constraints on the evolution of conspecific strains, we computed pangenomes for 155 phylogenetically diverse species (from ten phyla) using 7,000 high-quality genomes to each of which the respective habitats were assigned. Species habitat ubiquity was associated with several pangenome features. In particular, core-genome size was more important for ubiquity than accessory genome size. In general, environmental preferences had a stronger impact on pangenome evolution than phylogenetic inertia. Environmental preferences explained up to 49% of the variance for pangenome features, compared with 18% by phylogenetic inertia. This observation was robust when the dataset was extended to 10,100 species (59 phyla). The importance of environmental preferences was further accentuated by convergent evolution of pangenome features in a given habitat type across different phylogenetic clades. For example, the soil environment promotes expansion of pangenome size, while host-associated habitats lead to its reduction. Taken together, we explored the global principles of pangenome evolution, quantified the influence of habitat, and phylogenetic inertia on the evolution of pangenomes and identified criteria governing species ubiquity and habitat specificity.

RevDate: 2020-02-12

Badet T, Oggenfuss U, Abraham L, et al (2020)

A 19-isolate reference-quality global pangenome for the fungal wheat pathogen Zymoseptoria tritici.

BMC biology, 18(1):12 pii:10.1186/s12915-020-0744-3.

BACKGROUND: The gene content of a species largely governs its ecological interactions and adaptive potential. A species is therefore defined by both core genes shared between all individuals and accessory genes segregating presence-absence variation. There is growing evidence that eukaryotes, similar to bacteria, show intra-specific variability in gene content. However, it remains largely unknown how functionally relevant such a pangenome structure is for eukaryotes and what mechanisms underlie the emergence of highly polymorphic genome structures.

RESULTS: Here, we establish a reference-quality pangenome of a fungal pathogen of wheat based on 19 complete genomes from isolates sampled across six continents. Zymoseptoria tritici causes substantial worldwide losses to wheat production due to rapidly evolved tolerance to fungicides and evasion of host resistance. We performed transcriptome-assisted annotations of each genome to construct a global pangenome. Major chromosomal rearrangements are segregating within the species and underlie extensive gene presence-absence variation. Conserved orthogroups account for only ~ 60% of the species pangenome. Investigating gene functions, we find that the accessory genome is enriched for pathogenesis-related functions and encodes genes involved in metabolite production, host tissue degradation and manipulation of the immune system. De novo transposon annotation of the 19 complete genomes shows that the highly diverse chromosomal structure is tightly associated with transposable element content. Furthermore, transposable element expansions likely underlie recent genome expansions within the species.

CONCLUSIONS: Taken together, our work establishes a highly complex eukaryotic pangenome providing an unprecedented toolbox to study how pangenome structure impacts crop-pathogen interactions.

RevDate: 2020-02-12

Zwickl NF, Stralis-Pavese N, Schäffer C, et al (2020)

Comparative genome characterization of the periodontal pathogen Tannerella forsythia.

BMC genomics, 21(1):150 pii:10.1186/s12864-020-6535-y.

BACKGROUND: Tannerella forsythia is a bacterial pathogen implicated in periodontal disease. Numerous virulence-associated T. forsythia genes have been described, however, it is necessary to expand the knowledge on T. forsythia's genome structure and genetic repertoire to further elucidate its role within pathogenesis. Tannerella sp. BU063, a putative periodontal health-associated sister taxon and closest known relative to T. forsythia is available for comparative analyses. In the past, strain confusion involving the T. forsythia reference type strain ATCC 43037 led to discrepancies between results obtained from in silico analyses and wet-lab experimentation.

RESULTS: We generated a substantially improved genome assembly of T. forsythia ATCC 43037 covering 99% of the genome in three sequences. Using annotated genomes of ten Tannerella strains we established a soft core genome encompassing 2108 genes, based on orthologs present in > = 80% of the strains analysed. We used a set of known and hypothetical virulence factors for comparisons in pathogenic strains and the putative periodontal health-associated isolate Tannerella sp. BU063 to identify candidate genes promoting T. forsythia's pathogenesis. Searching for pathogenicity islands we detected 38 candidate regions in the T. forsythia genome. Only four of these regions corresponded to previously described pathogenicity islands. While the general protein O-glycosylation gene cluster of T. forsythia ATCC 43037 has been described previously, genes required for the initiation of glycan synthesis are yet to be discovered. We found six putative glycosylation loci which were only partially conserved in other bacteria. Lastly, we performed a comparative analysis of translational bias in T. forsythia and Tannerella sp. BU063 and detected highly biased genes.

CONCLUSIONS: We provide resources and important information on the genomes of Tannerella strains. Comparative analyses enabled us to assess the suitability of T. forsythia virulence factors as therapeutic targets and to suggest novel putative virulence factors. Further, we report on gene loci that should be addressed in the context of elucidating T. forsythia's protein O-glycosylation pathway. In summary, our work paves the way for further molecular dissection of T. forsythia biology in general and virulence of this species in particular.

RevDate: 2020-02-10

Sherman RM, SL Salzberg (2020)

Pan-genomics in the human genome era.

Nature reviews. Genetics pii:10.1038/s41576-020-0210-7 [Epub ahead of print].

Since the early days of the genome era, the scientific community has relied on a single 'reference' genome for each species, which is used as the basis for a wide range of genetic analyses, including studies of variation within and across species. As sequencing costs have dropped, thousands of new genomes have been sequenced, and scientists have come to realize that a single reference genome is inadequate for many purposes. By sampling a diverse set of individuals, one can begin to assemble a pan-genome: a collection of all the DNA sequences that occur in a species. Here we review efforts to create pan-genomes for a range of species, from bacteria to humans, and we further consider the computational methods that have been proposed in order to capture, interpret and compare pan-genome data. As scientists continue to survey and catalogue the genomic variation across human populations and begin to assemble a human pan-genome, these efforts will increase our power to connect variation to human diversity, disease and beyond.


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.

Electronic Scholarly Publishing
961 Red Tail Lane
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 )