FEMS microbiology ecology最新文献

While numerous environmental factors contribute to the spread of antibiotic resistance genes (ARGs), quantifying their relative contributions remains a fundamental challenge. Similarly, it is important to differentiate acute human health risks from environmental exposure, versus broader ecological risk of ARG evolution and spread across microbial taxa. Recent studies have proposed various methods for achieving such aims. Here, we introduce MetaCompare 2.0, which improves upon original MetaCompare pipeline by differentiating indicators of human health resistome risk (potential for human pathogens of acute resistance concern to acquire ARGs) from ecological resistome risk (overall mobility of ARGs and potential for pathogen acquisition). The updated pipeline's sensitivity was demonstrated by analyzing diverse publicly-available metagenomes from wastewater, surface water, soil, sediment, human gut, and synthetic microbial communities. MetaCompare 2.0 provided distinct rankings of the metagenomes according to both human health resistome risk and ecological resistome risk, with both scores trending higher when influenced by anthropogenic impact or other stress. We evaluated the robustness of the pipeline to sequence assembly methods, sequencing depth, contig count, and metagenomic library coverage bias. The risk scores were remarkably consistent despite variations in these technological aspects. We packaged the improved pipeline into a publicly-available web service (http://metacompare.cs.vt.edu/) that provides an easy-to-use interface for computing resistome risk scores and visualizing results.

Drylands' poly-extreme conditions limit edaphic microbial diversity and functionality. Furthermore, climate change exacerbates soil desiccation and salinity in most drylands. To better understand the potential effects of these changes on dryland microbial communities, we evaluated their taxonomic and functional diversities in two Southern African dryland soils with contrasting aridity and salinity. Fungal community structure was significantly influenced by aridity and salinity, while Bacteria and Archaea only by salinity. Deterministic homogeneous selection was significantly more important for bacterial and archaeal communities' assembly in hyperarid and saline soils when compared to those from arid soils. This suggests that niche partitioning drives bacterial and archaeal communities' assembly under the most extreme conditions. Conversely, stochastic dispersal limitations drove the assembly of fungal communities. Hyperarid and saline soil communities exhibited similar potential functional capacities, demonstrating a disconnect between microbial structure and function. Structure variations could be functionally compensated by different taxa with similar functions, as implied by the high levels of functional redundancy. Consequently, while environmental selective pressures shape the dryland microbial community assembly and structures, they do not influence their potential functionality. This suggests that they are functionally stable and that they could be functional even under harsher conditions, such as those expected with climate change.

Uptake hydrogenase (Hup) recycles H2 formed by nitrogenase during nitrogen fixation, thereby preserving energy. Among root nodule bacteria, most rhizobial strains examined are Hup-, while only one Hup-  Frankia inoculum had been identified. Previous analyses had led to the identification of two different [NiFe] hydrogenase syntons. We analysed the distribution of different types of [NiFe] hydrogenase in the genomes of different Frankia species. Our results show that Frankia strains can contain four different [NiFe] hydrogenase syntons representing groups 1f, 1h, 2a, and 3b according to Søndergaard, Pedersen, and Greening (HydDB: a web tool for hydrogenase classification and analysis. Sci Rep 2016;6:34212. https://doi.org/10.1038/srep34212.); no more than three types were found in any individual genome. The phylogeny of the structural proteins of groups 1f, 1h, and 2a follows Frankia phylogeny; the phylogeny of the accessory proteins does not consistently. An analysis of different [NiFe] hydrogenase types in Actinomycetia shows that under the most parsimonious assumption, all four types were present in the ancestral Frankia strain. Based on Hup activities analysed and the losses of syntons in different lineages of genome reduction, we can conclude that groups 1f and 2a are involved in recycling H2 formed by nitrogenase while group 1 h and group 3b are not.

Nematodes are common in most terrestrial environments, where populations are often known to undergo cycles of boom and bust. Useful in such scenarios, nematodes present developmental programs of diapause, giving rise to stress-resistant larvae and enabling dispersal in search of new resources. Best studied in Caenorhabditis elegans, stress resistant dauer larvae emerge under adverse conditions, primarily starvation, and migrate to new niches where they can resume development and reproduce. Caenorhabditis elegans is a bacterivore but has been shown to harbor a persistent and characteristic gut microbiome. While much is known about the gut microbiome of reproducing C. elegans, what dauers harbor is yet unknown. This is of interest, as dauers are those that would enable transmission of microbes between nematode generations and geographical sites, maintaining continuity of host-microbe interactions. Using culture-dependent as well as sequencing-based approaches, we examined the gut microbiomes of dauers emerging following population growth on ten different natural-like microbially diverse environments as well as on two defined communities of known gut commensals and found that dauers were largely devoid of gut bacteria. These results suggest that host gut-microbiome interactions in C. elegans are not continuous across successive generations and may reduce the likelihood of long-term worm-microbe coevolution.

Protist communities in the southern Pacific Ocean make a major contribution to global biogeochemical cycling, but remain understudied due to their remote location. We therefore have limited understanding of how large-scale physical gradients (e.g. temperature) and mesoscale oceanographic features (e.g. fronts) influence microeukaryote diversity in this region. We performed a high-resolution examination of protist communities along a latitudinal transect (>3000 km) at 150°W in the central southern Pacific Ocean that encompassed major frontal regions, including the subtropical front (STF), the subantarctic front (SAF), and the polar front (PF). We identified distinct microbial communities along the transect that were primarily delineated by the positions of the STF and PF. Some taxa were not constricted by these environmental boundaries and were able to span frontal regions, such as the colonial haptophyte Phaeocystis. Our findings also support the presence of a latitudinal diversity gradient (LDG) of decreasing diversity of the protist community with increasing latitude, although some individual taxa, notably the diatoms, do not adhere to this rule. Our findings show that oceanographic features and large-scale physical gradients have important impacts on marine protist communities in the southern Pacific Ocean that are likely to strongly influence their response to future environmental change.

Along the river-sea continuum, microorganisms are directionally dispersed by water flow while being exposed to strong environmental gradients. To compare the two assembly mechanisms that may strongly and differently influence metacommunity dynamics, namely homogenizing dispersal and heterogeneous selection, we characterized the total (16S rRNA gene) and putatively active (16S rRNA transcript) bacterial communities in the Pearl River-South China Sea Continuum, during the wet (summer) and dry (winter) seasons using high-throughput sequencing. Moreover, well-defined sampling was conducted by including freshwater, oligohaline, mesohaline, polyhaline, and marine habitats. We found that heterogeneous selection exceeded homogenizing dispersal in both the total and active fractions of bacterial communities in two seasons. However, homogeneous selection was prevalent (the dominant except in active bacterial communities during summer), which was primarily due to the bacterial communities' tremendous diversity (associated with high rarity) and our specific sampling design. In either summer or winter seasons, homogeneous and heterogeneous selection showed higher relative importance in total and active communities, respectively, implying that the active bacteria were more responsive to environmental gradients than were the total bacteria. In summary, our findings provide insight into the assembly of bacterial communities in natural ecosystems with high spatial connectivity and environmental heterogeneity.

Gut microbial diversity influences the health and vitality of the host, yet it is itself affected by internal and external factors, including land-use. The impact of land-use practices on wild rodents' gut microbiomes remains understudied, despite their abundance and potential as reservoirs for zoonotic pathogens. We examined the bacterial and fungal gut microbiomes of bank voles (Myodes glareolus) and common voles (Microtus arvalis) across grassland and forest habitats with varying land-use intensities and types. We collected rodents seasonally and used 16S rRNA and ITS amplicon sequencing for microbe identification. We found significant differences in alpha and beta diversities between the species, with M. arvalis exhibiting higher diversity. Seasonality emerged as a prominent factor influencing microbial diversity, with significant variations between sampling months. While land-use affects the gut microbiome, its impact is subordinate to seasonal variations. Differential abundance analysis underscores the dynamic nature of microbial composition, with seasonal changes playing a predominant role. Overall, our findings highlight the significant influence of seasonality on gut microbiome diversity and composition in wild rodents, reflecting dietary shifts associated with seasonal changes. Understanding the interplay between environmental factors and microbial communities in wild rodents enahnces our knowledge of ecosystem health and resilience, warranting further investigation.

Marine Stramenopiles (MAST) were first described two decades ago through ribosomal RNA gene (rRNA gene) sequences from marine surveys of microbial eukaryotes. MAST comprise several independent lineages at the base of the Stramenopiles. Despite their prevalence in the ocean, the majority of MAST diversity remains uncultured. Previous studies, mainly in marine environments, have explored MAST's cell morphology, distribution, trophic strategies, and genomics using culturing-independent methods. In comparison, less is known about their presence outside marine habitats. Here, we analyse the extensive EukBank dataset to assess the extent to which MAST can be considered marine protists. Additionally, by incorporating newly available rRNA gene sequences, we update Stramenopiles phylogeny, identifying three novel MAST lineages. Our results indicate that MAST are primarily marine with notable exceptions within MAST-2 and MAST-12, where certain subclades are prevalent in freshwater and soil habitats. In the marine water column, only a few MAST species, particularly within clades -1, -3, -4, and -7, dominate and exhibit clear latitudinal distribution patterns. Overall, the massive sequencing dataset analysed in our study confirms and partially expands the previously described diversity of MASTs groups and underscores the predominantly marine nature of most of these uncultured lineages.

Skin microbes play an important role in amphibian tissue regeneration. Xenopus spp. (African clawed frogs) are well-established model organisms, and standard husbandry protocols, including use of antibiotics, may affect experimental outcomes by altering bacterial assemblages. It is therefore essential to improve knowledge of Xenopus bacterial community characteristics and inheritance. We undertook bacterial 16S rRNA gene sequencing and source tracking of a captive Xenopus laevis colony, including various life stages and environmental samples across multiple aquarium systems. Tank environments supported the most complex bacterial communities, while egg jelly bacteria were the most diverse of frog life stages; tadpole bacterial communities were relatively simple. Rhizobium (Proteobacteria) and Chryseobacterium (Bacteroidota) were dominant in tadpoles, whereas Chryseobacterium, Vogesella (Proteobacteria), and Acinetobacter (Proteobacteria) were common in females. Tadpoles received approximately two-thirds of their bacteria via vertical transmission, though 23 genera were differentially abundant between females and tadpoles. Female frog skin appears to select for specific taxa, and while tadpoles inherit a proportion of their skin bacteria from females via the egg, they support a distinct and less diverse community. The outcomes of this study suggest the impacts of breaking the bacterial transmission chain with antibiotic treatment should be considered when raising tadpoles for experimental purposes.

The Asian tiger mosquito Aedes albopictus is well adapted to urban environments and takes advantage of the artificial containers that proliferate in anthropized landscapes. Little is known about the physicochemical, pollutant, and microbiota compositions of Ae. albopictus-colonized aquatic habitats and whether these properties differ with noncolonized habitats. We specifically addressed this question in French community gardens by investigating whether pollution gradients (characterized either by water physicochemical properties combined with pollution variables or by the presence of organic molecules in water) influence water microbial composition and then the presence/absence of Ae. albopictus mosquitoes. Interestingly, we showed that the physicochemical and microbial compositions of noncolonized and colonized waters did not significantly differ, with the exception of N2O and CH4 concentrations, which were higher in noncolonized water samples. Moreover, the microbial composition of larval habitats covaried differentially along the pollution gradients according to colonization status. This study opens new avenues on the impact of pollution on mosquito habitats in urban areas and raises questions on the influence of biotic and abiotic interactions on adult life-history traits and their ability to transmit pathogens to humans.