Microbial Genomics

Journal: Microbial Genomics

Abbreviation

Microb Genom

Publisher

Microbiology Society

ISSN

2057-5858

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Publications1 - 10 of 12

Host–virome associations in the weathering crust of a rapidly retreating temperate Alpine glacier
Varliero, Gilda; Bauder, Andreas; Stierli, Beat; et al. (2025)
Microbial Genomics
Glaciers are retreating rapidly, altering ecosystem dynamics and increasing meltwater outflow into populated areas. Understanding microbial-virome interactions is crucial for predicting the consequences of this release. We sampled ice from four shallow pits in the weathering crust of the Rhonegletscher, Swiss Alps, and found a microbiome dominated by bacteria and microeukaryotes, alongside a metavirome infecting both groups. Viruses exhibited variable host specificity, with some targeting particular taxa and others showing a broader infectivity range. Variable genomic regions, including metagenomic and metaviromic islands, were enriched in genes related to replication, recombination, repair and transposable elements. Detected auxiliary metabolic genes were primarily involved in host coenzyme biosynthesis, uptake or utilization and in altering bacterial methylation patterns to evade detection. These findings underscore the major role of viruses in regulating microbial dynamics in glaciers and their potential downstream environmental impacts.
Tracking SARS-CoV-2 variants of concern in wastewater: an assessment of nine computational tools using simulated genomic data
Sutcliffe, Steven G.; Kraemer, Susanne A.; Ellmen, Isaac; et al. (2024)
Microbial Genomics
Wastewater-based surveillance (WBS) is an important epidemiological and public health tool for tracking pathogens across the scale of a building, neighbourhood, city, or region. WBS gained widespread adoption globally during the SARS-CoV-2 pandemic for estimating community infection levels by qPCR. Sequencing pathogen genes or genomes from wastewater adds information about pathogen genetic diversity, which can be used to identify viral lineages (including variants of concern) that are circulating in a local population. Capturing the genetic diversity by WBS sequencing is not trivial, as wastewater samples often contain a diverse mixture of viral lineages with real mutations and sequencing errors, which must be deconvoluted computationally from short sequencing reads. In this study we assess nine different computational tools that have recently been developed to address this challenge. We simulated 100 wastewater sequence samples consisting of SARS-CoV-2 BA.1, BA.2, and Delta lineages, in various mixtures, as well as a Delta-Omicron recombinant and a synthetic 'novel' lineage. Most tools performed well in identifying the true lineages present and estimating their relative abundances and were generally robust to variation in sequencing depth and read length. While many tools identified lineages present down to 1 % frequency, results were more reliable above a 5 % threshold. The presence of an unknown synthetic lineage, which represents an unclassified SARS-CoV-2 lineage, increases the error in relative abundance estimates of other lineages, but the magnitude of this effect was small for most tools. The tools also varied in how they labelled novel synthetic lineages and recombinants. While our simulated dataset represents just one of many possible use cases for these methods, we hope it helps users understand potential sources of error or bias in wastewater sequencing analysis and to appreciate the commonalities and differences across methods.
Genomic relatedness and clinical significance of Streptococcus mitis strains isolated from the urogenital tract of sexual partners
Roese Mores, Carine; Price, Travis K.; Wolff, Birte; et al. (2021)
Microbial Genomics
Research into the lower urinary tract (LUT) microbiota has primarily focused on its relationship to LUT symptoms (LUTS), taking snapshots of these communities in individuals with and without LUTS. While certain bacterial taxa have been associated with LUTS, or the lack thereof, the temporal dynamics of this community were largely unknown. Recently, we conducted a longitudinal study and found that vaginal intercourse resulted in a shift in species richness and diversity within the LUT microbiota. This is particularly relevant as frequent vaginal intercourse is a major risk factor for urinary tract infection (UTI) in premenopausal women (Aydin et al. Int Urogynecol J 2015;26:795–804). To further investigate the relationship between vaginal intercourse and LUT microbiota, here we present the results of a 3 week study in which daily urogenital specimens were collected from a female participant and her male sexual partner. Consistent with our previous findings, the LUT microbiota changed after vaginal intercourse, most notably a high abundance of Streptococcus mitis was observed post-coitus. We isolated and sequenced S. mitis from both sexual partners finding that: (i) the S. mitis isolates from the female partner’s urogenital tract were genomically similar throughout the duration of the study, and (ii) they were related to one isolate from the male partner’s oral cavity collected at the end of the study, suggesting transmission between the two individuals. We hypothesize that blooms in S. mitis after vaginal intercourse may play a role in coitus-related UTI. We found that a S. mitis isolate, in contrast to a Lactobacillus jensenii isolate displaced after vaginal intercourse, cannot inhibit the growth of uropathogenic Escherichia coli . Thus, this bloom in S. mitis may provide a window of opportunity for a uropathogen to colonize the LUT.
Gene conversion and duplication contribute to genetic variation in an outbreak of Mycobacterium tuberculosis
Stritt, Christoph; Reitsma, Michelle; Garcia Marin, Ana Maria; et al. (2025)
Microbial Genomics
Repeats are the most diverse and dynamic but also the least well-understood component of microbial genomes. For all we know, repeat-associated mutations such as duplications, deletions, inversions and gene conversion might be as common as point mutations, but because of short-read myopia and methodological bias, they have received much less attention. Long-read DNA sequencing opens the perspective of resolving repeats and systematically investigating the mutations they induce. For this study, we assembled the genomes of 16 closely related strains of the bacterial pathogen Mycobacterium tuberculosis from Pacific Biosciences HiFi reads, with the aim of characterizing the full spectrum of DNA polymorphisms. We found that complete and accurate genomes can be assembled from HiFi reads, with read size being the main limitation in the presence of duplications. By combining a reference-free pangenome graph with extensive repeat annotation, we identified 110 variants, 58 of which could be assigned to repeat-associated mutational mechanisms such as strand slippage and homologous recombination. Whilst recombination events were less frequent than point mutations, they affected large regions and introduced multiple variants at once, as shown by three gene conversion events and a duplication of 7.3 kb that involved ppe18 and ppe57, two genes possibly involved in immune subversion. The vast majority of variants were present in single isolates, such that phylogenetic resolution was only marginally increased when estimating a tree from complete genomes. Our study shows that the contribution of repeat-associated mechanisms of mutation can be similar to that of point mutations at the microevolutionary scale of an outbreak. A large reservoir of unstudied genetic variation in this 'monomorphic' bacterial pathogen awaits investigation.
Phylodynamic estimation of the within-host evolutionary rate of extended-spectrum beta-lactamase-producing Enterobacterales
Windels, Etthel; Aguilar-Bultet, Lisandra; Vock, Isabelle; et al. (2025)
Microbial Genomics
Despite their clinical relevance, the within-host evolution of extended-spectrum beta-lactamase (ESBL)-producing Enterobacterales is still poorly understood. To estimate the within-host evolutionary rates of ESBL-producing Escherichia coli and Klebsiella pneumoniae species complex, we fitted phylodynamic models to genomic sequence data of longitudinally collected rectal swabs from 63 colonized hospital patients. We estimated an average within-host evolutionary rate of 7.71e-07 [4.60e-07,1.10e-06] mutations/site/year for E. coli and 4.20e-07 [1.57e-07,7.14e-07] mutations/site/year for the K. pneumoniae species complex, with limited variation observed across patients and sequence types. These estimates are presumably the most accurate reported so far and are useful for future epidemiological and evolutionary studies.
Comparative 'omics analyses differentiate Mycobacterium tuberculosis and Mycobacterium bovis and reveal distinct macrophage responses to infection with the human and bovine tubercle bacilli
Malone, Kerri M.; Rue-Albrecht, Kevin; Magee, David A.; et al. (2018)
Microbial Genomics
Members of the Mycobacterium tuberculosis complex (MTBC) are the causative agents of tuberculosis in a range of mammals, including humans. A key feature of MTBC pathogens is their high degree of genetic identity yet distinct host tropism. Notably, while Mycobacterium bovis is highly virulent and pathogenic for cattle, the human pathogen M. tuberculosis is attenuated in cattle. Previous research also suggests that host preference amongst MTBC members has a basis in host innate immune responses. To explore MTBC host tropism, we present in-depth profiling of the MTBC reference strains M. bovis AF2122/97 and M. tuberculosis H37Rv at both the global transcriptional and the translational level via RNA-sequencing and SWATH MS. Furthermore, a bovine alveolar macrophage infection time course model was used to investigate the shared and divergent host transcriptomic response to infection with M. tuberculosis H37Rv or M. bovis AF2122/97. Significant differential expression of virulence-associated pathways between the two bacilli was revealed, including the ESX-1 secretion system. A divergent transcriptional response was observed between M. tuberculosis H37Rv and M. bovis AF2122/97 infection of bovine alveolar macrophages, in particular cytosolic DNA-sensing pathways at 48 h post-infection, and highlights a distinct engagement of M. bovis with the bovine innate immune system. The work presented here therefore provides a basis for the identification of host innate immune mechanisms subverted by virulent host-adapted mycobacteria to promote their survival during the early stages of infection.
Genomic epidemiology of Mycobacterium bovis infection in sympatric badger and cattle populations in Northern Ireland
Akhmetova, Assel; Guerrero, Jimena; McAdam, Paul; et al. (2023)
Microbial Genomics
Bovine tuberculosis (bTB) is a costly, epidemiologically complex, multi-host, endemic disease. Lack of understanding of transmission dynamics may undermine eradication efforts. Pathogen whole-genome sequencing improves epidemiological inferences, providing a means to determine the relative importance of inter- and intra-species host transmission for disease persistence. We sequenced an exceptional data set of 619 Mycobacterium bovis isolates from badgers and cattle in a 100 km2 bTB 'hotspot' in Northern Ireland. Historical molecular subtyping data permitted the targeting of an endemic pathogen lineage, whose long-term persistence provided a unique opportunity to study disease transmission dynamics in unparalleled detail. Additionally, to assess whether badger population genetic structure was associated with the spatial distribution of pathogen genetic diversity, we microsatellite genotyped hair samples from 769 badgers trapped in this area. Birth death models and TransPhylo analyses indicated that cattle were likely driving the local epidemic, with transmission from cattle to badgers being more common than badger to cattle. Furthermore, the presence of significant badger population genetic structure in the landscape was not associated with the spatial distribution of M. bovis genetic diversity, suggesting that badger-to-badger transmission is not playing a major role in transmission dynamics. Our data were consistent with badgers playing a smaller role in transmission of M. bovis infection in this study site, compared to cattle. We hypothesize, however, that this minor role may still be important for persistence. Comparison to other areas suggests that M. bovis transmission dynamics are likely to be context dependent, with the role of wildlife being difficult to generalize.
Shotgun metagenomics reveals distinct functional diversity and metabolic capabilities between 12 000-year-old permafrost and active layers on Muot da Barba Peider (Swiss Alps)
Perez-Mon, Carla; Qi, Weihong; Vikram, Surendra; et al. (2021)
Microbial Genomics
The warming-induced thawing of permafrost promotes microbial activity, often resulting in enhanced greenhouse gas emissions. The ability of permafrost microorganisms to survive the in situ sub-zero temperatures, their energetic strategies and their metabolic versatility in using soil organic materials determine their growth and functionality upon thawing. Hence, functional characterization of the permafrost microbiome, particularly in the underexplored mid-latitudinal alpine regions, is a crucial first step in predicting its responses to the changing climate, and the consequences for soil–climate feedbacks. In this study, for the first time, the functional potential and metabolic capabilities of a temperate mountain permafrost microbiome from central Europe has been analysed using shotgun metagenomics. Permafrost and active layers from the summit of Muot da Barba Peider (MBP) [Swiss Alps, 2979 m above sea level (a.s.l.)] revealed a strikingly high functional diversity in the permafrost (north-facing soils at a depth of 160 cm). Permafrost metagenomes were enriched in stress-response genes (e.g. cold-shock genes, chaperones), as well as in genes involved in cell defence and competition (e.g. antiviral proteins, antibiotics, motility, nutrient-uptake ABC transporters), compared with active-layer metagenomes. Permafrost also showed a higher potential for the synthesis of carbohydrate-active enzymes, and an overrepresentation of genes involved in fermentation, carbon fixation, denitrification and nitrogen reduction reactions. Collectively, these findings demonstrate the potential capabilities of permafrost microorganisms to thrive in cold and oligotrophic conditions, and highlight their metabolic versatility in carbon and nitrogen cycling. Our study provides a first insight into the high functional gene diversity of the central European mountain permafrost microbiome. Our findings extend our understanding of the microbial ecology of permafrost and represent a baseline for future investigations comparing the functional profiles of permafrost microbial communities at different latitudes.
Microbial genetic potential differs among cryospheric habitats of the Damma glacier
Feng, Maomao; Robinson, Serina; Qi, Weihong; et al. (2024)
Microbial Genomics
Climate warming has led to glacier retreat worldwide. Studies on the taxonomy and functions of glacier microbiomes help us better predict their response to glacier melting. Here, we used shotgun metagenomic sequencing to study the microbial functional potential in different cryospheric habitats, i.e. surface snow, supraglacial and subglacial sediments, subglacial ice, proglacial stream water and recently deglaciated soils. The functional gene structure varied greatly among habitats, especially for snow, which differed significantly from all other habitats. Differential abundance analysis revealed that genes related to stress responses (e.g. chaperones) were enriched in ice habitat, supporting the fact that glaciers are a harsh environment for microbes. The microbial metabolic capabilities related to carbon and nitrogen cycling vary among cryospheric habitats. Genes related to auxiliary activities were overrepresented in the subglacial sediment, suggesting a higher genetic potential for the degradation of recalcitrant carbon (e.g., lignin). As for nitrogen cycling, genes related to nitrogen fixation were more abundant in barren proglacial soils, possibly due to the presence of Cyanobacteriota in this habitat. Our results deepen our understanding of microbial processes in glacial ecosystems, which are vulnerable to ongoing global warming, and they have implications for downstream ecosystems.
Population genomics of transposable element activation in the highly repressive genome of an agricultural pathogen
dos Santos Pereira, Danilo A.; Oggenfuss, Ursula; McDonald, Bruce A.; et al. (2021)
Microbial Genomics
The activity of transposable elements (TEs) can be an important driver of genetic diversity with TE- mediated mutations having a wide range of fitness consequences. To avoid deleterious effects of TE activity, some fungi have evolved highly sophisticated genomic defences to reduce TE proliferation across the genome. Repeat- induced point mutation (RIP) is a fungal- specific TE defence mechanism efficiently targeting duplicated sequences. The rapid accumulation of RIPs is expected to deactivate TEs over the course of a few generations. The evolutionary dynamics of TEs at the population level in a species with highly repressive genome defences is poorly understood. Here, we analyse 366 whole- genome sequences of Parastagonospora nodorum, a fungal pathogen of wheat with efficient RIP. A global population genomics analysis revealed high levels of genetic diversity and signs of frequent sexual recombination. Contrary to expectations for a species with RIP, we identified recent TE activity in multiple populations. The TE composition and copy numbers showed little divergence among global populations regardless of the demographic history. Miniature inverted- repeat transposable elements (MITEs) and terminal repeat retrotransposons in miniature (TRIMs) were largely underlying recent intra- species TE expansions. We inferred RIP footprints in individual TE families and found that recently active, high- copy TEs have possibly evaded genomic defences. We find no evidence that recent positive selection acted on TE- mediated mutations rather that purifying selection maintained new TE insertions at low insertion frequencies in populations. Our findings highlight the complex evolutionary equilibria established by the joint action of TE activity, selection and genomic repression.

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Journal: Microbial Genomics

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