Microbial Genomics最新文献

Marine sponges are found in all of the world's oceans, from the surface waters to the deepest abyssal zones. The marine sponge holobiont is a rich source of microbial and chemical diversity. Up to 63 bacterial phyla have been observed to be associated with sponges, and thousands of unique natural products have been extracted from sponges or their microbial symbionts. However, sponges from the deep sea and their associated microbial communities are relatively understudied, largely due to sampling-associated difficulties. Secondary metabolism biosynthetic gene clusters are phylogenetically distinct and hold the potential to produce novel chemistry with potential pharmacological or industrial utility. In order to gain further insights into the microbiome of the deep-sea sponge Inflatella pellicula, the metagenome of this sponge, sampled from a depth of 2,900 m, was sequenced. A large fraction of the sequence reads appeared to be 'biological dark matter' and could not be taxonomically classified. Further, unlike similar studies from different marine ecosystems, relatively few metagenome-assembled genomes (MAGs) could be assembled, and relatively few secondary metabolism biosynthetic gene clusters were identified. The identified clusters were, however, very dissimilar to known characterized clusters, but some shared similarities with clusters annotated in MAGs assembled from sponge metagenomes from disparate geographic locations. Therefore, renewed efforts to cultivate the hosts of these gene clusters may yield valuable small-molecule natural products.

The genus Vibrio encompasses globally relevant pathogens, of which Vibrio cholerae is the best known due to its role in cholera. Closely related species within the Cholerae clade - Vibrio paracholerae, Vibrio metoecus and Vibrio tarriae - were long misclassified as non-O1/O139 Vibrio cholerae. The objective of this study was to analyse all 13,000+ available V. cholerae genomes in GenBank to determine the presence of species from the Cholerae clade. Genome-wide analyses using Mash, whole-genome-based Average Nucleotide Identity and digital DNA-DNA hybridization reclassified 190 unique genomes as V. paracholerae, while V. metoecus and V. tarriae were not detected. Phylogenomic analyses revealed that V. paracholerae forms distinct lineages, spanning clinical, environmental and animal sources over a period of more than a century. Virulence profiling revealed the absence of cholera toxin and toxin-coregulated pilus; however, most genomes exhibited other virulence factors, including haemolysins, RTX toxins, cholix toxin and a conserved type VI secretion system. Resistome analysis revealed multiple antibiotic resistance genes, several of which were embedded within superintegron regions, reinforcing the role of V. paracholerae as a reservoir of resistance determinants. Importantly, we identified five putative gene markers with high sensitivity and specificity for discriminating the two species, providing a tool for diagnostic applications and epidemiological surveillance. These findings reveal an unsuspected epidemiological scenario for V. paracholerae, which should be considered in clinical monitoring and public health strategies involving the Cholerae clade.

Vibrio europaeus has emerged as a significant pathogen in shellfish aquaculture, causing mass mortality outbreaks in key bivalve species and leading to severe economic losses for the industry. Studies on the structure and characteristics of the accessory genome in aquaculture pathogens remain scarce, despite its crucial role in evolutionary and ecological adaptation. The accessory genome provides indeed genetic variability that enables rapid responses to environmental challenges, host adaptation and selective pressures such as antibiotics or phage predation. Here, we present the first comprehensive comparative genomic analysis of the V. europaeus pangenome to investigate the structural organization and functional content of its accessory genome. The soft mobilome of V. europaeus comprises 73% of accessory genes and 44% of the total pangenome, including non-chromosomic (plasmids) and chromosomic genetic elements such as prophages, integrative and conjugative/mobilizable elements, phage satellites and other mobile genetic elements (MGEs) designated as unclassified chromosomic regions of genomic plasticity (unclassified chromosomic RGPs). Among accessory elements, unclassified chromosomic RGPs were the primary drivers of evolutionary dynamics in V. europaeus, acting as the main genetic reservoir of anti-phage defence systems and antimicrobial resistance genes. Notably, the identification of abundant insertion hotspots in chromosomic genetic elements facilitates the rapid acquisition of anti-phage defence systems, thereby enabling rapid turnover of these systems and enhancing host fitness. In addition, novel pVE1-like plasmids (>300 kb) - only found in this species and its closest relative Vibrio tubiashii - emerged as the largest and most ubiquitous MGEs in V. europaeus. These plasmids encode the highest number of virulence genes and secondary metabolite biosynthetic genes, as well as a remarkable diversity of anti-phage defence systems among closely related strains. Although the genome dataset analysed here is limited to strains isolated from moribund/dead animals in aquaculture environments, this study provides new insights into the role of accessory genetic elements in the evolution, adaptation and diversification of the shellfish pathogen V. europaeus. The findings reveal the complexity and plasticity of its pangenome and highlight the importance of RGPs and plasmids in bacterial fitness.

Background. The propensity of Streptococcus pyogenes (group A Streptococcus) to invade normally sterile sites and cause invasive group A Streptococcus (iGAS) disease varies across strains, which are classified using the emm gene. Between 2015 and 2017, multistate iGAS surveillance identified an ~150-fold increase of one particular emm type, emm49. This genomic epidemiological analysis aimed to identify bacterial, patient and societal factors associated with this expansion.Methods. We analysed 1322 emm49 iGAS cases and the genome sequences of the clinical isolates acquired through the population-based Active Bacterial Core surveillance during 2015-2022. For each invasive case, we received both a cultured isolate and a standardized case report form that included basic demographic attributes and risk factors of infection. A phylogeographic analysis was performed to reconstruct the divergence times and spatial dispersal history within our emm49 collection.Results. Compared to other emm types, emm49 cases were more common in males (63.5% vs. 58.3%, P=0.0143), in people experiencing homelessness (34.0% vs. 17.5%, P<0.0001) and in people who inject drugs (23.7% vs. 13.1%, P<0.0001). Time-scaled phylogeographic analysis estimated that the most recent common ancestor of the post-2015 expansion isolates occurred around 2004 and that emm49 emerged in the western USA.Conclusion. Our findings suggest that the current nationwide outbreak may have originated from the introduction of emm49 into disadvantaged (homeless and/or injecting drug users) adult subpopulations. This study underscores how social marginalization and broader social determinants of health can shape iGAS strain epidemiology in the USA.

Metagenomic sequencing of clinical samples has significantly enhanced our understanding of microbial communities. However, microbial contamination and host-derived DNA remain a major obstacle to accurate data interpretation. Here, we present a methodology called 'Stop-Check-Go' for detecting and mitigating contaminants in metagenomic datasets obtained from neonatal patient samples (nasal and rectal swabs). This method incorporates laboratory and bioinformatics work combining a prevalence method, coverage estimation and microbiological reports. We compared the 'Stop-Check-Go' decontamination system with other published decontamination tools and commonly found poor performance in decontaminating microbiologically negative patients (false positives). We emphasize that host DNA decreased by an average of 76% per sample using a lysis method and was further reduced during post-sequencing analysis. Microbial species were classified as putative contaminants and assigned to 'Stop' in nearly 60% of the dataset. The 'Stop-Check-Go' system was developed to address the specific need of decontaminating low-biomass samples, where existing tools primarily designed for short-read metagenomic data showed limited performance.

In 2019, an outbreak of acute haemorrhagic diarrhoea (AHD) in dogs in Norway was linked to Providencia alcalifaciens. A marked increase in diarrhoeal cases in dogs during the autumn, along with the frequent identification of P. alcalifaciens in affected dogs, supports its role as a causative agent in seasonal diarrhoea in dogs in Norway. Previous phylogenetic studies have revealed two major genetic lineages of P. alcalifaciens, one of which is associated with diarrhoeal disease and carries a plasmid-borne type 3 transport system (T3SS_1a). The aim of this study was to place Norwegian P. alcalifaciens isolates in a global phylogenetic context and to characterize the distribution of putative virulence-associated genes (VAGs) in isolates from dogs with AHD. Whole-genome sequencing was performed on 273 isolates, and 48 publicly available genomes were included for comparative analyses. Bioinformatic processing and phylogenetic analyses were conducted on the complete dataset of 321 P. alcalifaciens genomes. VAGs were identified using ABRicate and two virulence gene databases. Phylogenetic analyses revealed two main clusters, A and B. Most isolates from sick dogs belonged to cluster A, particularly to subcluster A-1 - the largest of five subclusters - which primarily contained isolates from sick dogs. All isolates in subclusters A-1 and A-4 harboured genes encoding T3SS_1a, a type II secretion system and the effector genes stcE, yopJ and cdtA-C. blast searches using closed reference genomes showed high sequence identity (>90%) to plasmid elements in 196 of 197 isolates from subclusters A-1 and A-4, suggesting plasmid-mediated acquisition of virulence factors. These findings support that specific genetic variants of P. alcalifaciens, particularly those in subclusters A-1 and A-4, exhibit increased virulence potential and are associated with AHD in dogs. The high proportion of isolates from clinically affected dogs, including many from the 2019 outbreak, further underscores the link between subcluster A-1 and disease.

Despite the recent expansion of culture-independent analyses of animal faecal microbiomes, many lineages remain understudied. Marsupials represent one such group, where, despite their iconic status, direct sequencing-based analyses remain limited. Here, we present a metagenomic and metabolomic exploration of the faecal microbiomes of 23 Diprotodontia marsupials, producing a reference set of 3,868 prokaryotic and 12,142 viral metagenome-assembled genomes, the majority (>80 %) of which represent novel species. As with other animals, host phylogeny is the primary driver of microbiome composition, including distinct profiles for two eucalypt folivore specialists (koalas and southern greater gliders), suggesting independent solutions to this challenging diet. Expansion of several bacterial and viral lineages was observed in these and other marsupial hosts that may provide adaptive benefits. Antimicrobial resistance genes were significantly more prevalent in captive than wild animals, likely reflecting human interaction. This molecular dataset contributes to our ongoing understanding of animal faecal microbiomes.

The hospital environment plays a critical role in the transmission of infectious diseases. Surveillance methods often rely on selective enrichment or deep metagenomic sequencing, which both have significant drawbacks in terms of community resolution and cost. Plate sweeps provide a practical moderate approach to cultivate a wide range of bacteria, capturing more diversity than a single colony pick without high sequencing costs. Here, we use this approach to characterize a newly built hospital intensive care unit (ICU) in Queensland, Australia. Between November 2023 and February 2024, we sampled 78 sites within an 8-bed private hospital ICU pre- and post-patient introduction to the environment. Samples were enriched on non-selective media before DNA was extracted from whole plate sweeps and sequenced using Illumina. We assessed species, antimicrobial resistance (AMR) genes, virulence genes and transmission across all samples and between the pre- and post-patient samples using Kraken2, AbritAMR and Tracs. While the rate of positive microbial growth within the ICU environment did not change significantly pre- and post-patient introduction, the post-patient microbiome consisted of largely different bacterial species; of 22 genera identified, only 3 genera were represented at both timepoints. Post-patient samples were enriched in AMR genes, including resistance to fosfomycin, quinolones and beta-lactams. Common genera identified post-patient were Pseudomonas, Delftia and Stenotrophomonas, often associated with areas of plumbing. Cluster analysis identified 17 possible transmission links from a single timepoint, highlighting several areas in the ICU (e.g. communal bathrooms) as key areas for transmission. We demonstrate the utility of plate sweeps as a means of economical non-selective environmental surveillance and highlight their ability to identify hotspots of transmission within a hospital ward that could be targeted by infection control prior to an outbreak of a more serious pathogen.

Escherichia coli resistant to third-generation cephalosporins (3GCs) is a WHO priority pathogen due to its antimicrobial resistance (AMR). In high-income countries, such as Australia, 3GC-resistant E. coli are a common cause of extra-intestinal infections in both healthcare and community settings. Long-term targeted surveillance efforts of AMR in E. coli routinely identify E. coli as a leading pathogen in bacteraemic infections. To date, there has been limited detailed genomic analysis of the drug-resistant E. coli circulating in Australian clinical settings. Here, we sought to explore the genomic diversity of 3GC-resistant isolates (mediated by extended-spectrum beta-lactamase or AmpC), collected from four hospital networks in Melbourne, Australia. We establish the population structure, identifying ten main lineages in addition to multiple other sequence types, demonstrating 3GC resistance has emerged in multiple genetic backgrounds. We show diversity of accessory genome features, including surface antigens, AMR and plasmid profiles. A total of 117 serotypes and 47 capsular loci were detected, with diversity observed within and between main lineages. We identified 17 unique 3GC resistance mechanisms disseminated across the E. coli population, which co-occurred in different combinations of AMR genes and plasmid replicons. We explored the use of genomic clustering as an approach to detect different population dynamics, identifying 99 clusters of which only 15 had more than 5 isolates. This study provides a comprehensive snapshot of these drug-resistant E. coli in Australia over this time period and will serve as a baseline for future studies of clinical and community drug-resistant isolates in Australia.

Streptococcus suis is a major pig pathogen with zoonotic potential, posing an occupational risk to farmers and meat handlers. We characterized 110 S. suis strains from diseased pigs in Ireland (2005-2022) using whole-genome sequencing to investigate population structure and phage-host dynamics. We identified 15 distinct serotypes, with serotypes 9 and 2 being the most dominant. In silico multi-locus sequence typing revealed high diversity within the collection, identifying several sequence types (STs), including 26 novel STs. Investigation of strain-level genomic clustering using PopPUNK against global S. suis genomes showed that the Irish isolates were phylogenetically dispersed across the broader global S. suis population rather than clustering in a single clonal group. The majority of Irish isolates fall within the ten established pathogenic lineages, including the highly virulent zoonotic lineage 1. A locally persistent clonal lineage was identified among Irish isolates, showing minimal genetic variation over a decade.Prophage analysis revealed novel viral taxa that were interspersed among known streptococcal phages, rather than clustering distinctly. Restriction-modification systems were the predominant anti-viral defence systems identified across genomes. CRISPR-Cas systems were present in limited strains but showed substantial targeting bias toward full-length prophages, indicating ongoing phage pressure. CRISPR spacers matched non-S. suis streptococcal phages, and phylogenomic analysis revealed that Vansinderenvirus phages clustered with S. suis rather than other Streptococcus thermophilus phages, suggesting evolutionary connections between phage lineages infecting different streptococci.This study presents the first comprehensive genomic characterization of S. suis in Ireland, revealing a diverse population with significant implications for animal and human health.