FEMS microbiology ecology最新文献

Thermal springs harbour microorganisms, often dominated by cyanobacteria, which form biofilms and microbial mats. These phototrophic organisms release organic exudates into their immediate surroundings, attracting heterotrophic bacteria that contribute to the diversity and functioning of these ecosystems. In this study, the microbial mats from a hydrothermal pool in the Ksar Ghilane oasis in the Grand Erg Oriental of the DesertTunisia, were collected to obtain cyanobacterial cultures formed by single cyanobacterial species. High throughput analysis showed that while the microbial mat hosted diverse cyanobacteria, laboratory cultures selectively enriched cyanobacteria from the Leptolyngbya, Nodosilinea and Arthronema. Per each of these genera, multiple non-axenic uni-cyanobacterial cultures were established, totalling 41 cultures. Cyanobacteria taxa mediated the assembly of distinct heterotrophic bacterial communities, with members of the Proteobacteria and Actinobacteria phyla dominating. The bacterial communities of uni-cyanobacterial cultures were densely interconnected, with heterotrophic bacteria preferentially co-occurring with each other. Our study highlighted the complex structures of non-axenic uni-cyanobacterial cultures, where taxonomically distinct cyanobacteria consistently associate with specific groups of heterotrophic bacteria. The observed associations were likely driven by common selection pressures in the laboratory, such as cultivation conditions and specific hosts, and may not necessarily reflect the microbial dynamic occurring in the spring microbial mats.

Diet profoundly influences the composition of an animal's microbiome, especially in holometabolous insects, offering a valuable model to explore the impact of diet on gut microbiome dynamics throughout metamorphosis. Here, we use monarch butterflies (Danaus plexippus), specialist herbivores that feed as larvae on many species of chemically well-defined milkweed plants (Asclepias sp.), to investigate the impacts of development and diet on the composition of the gut microbial community. While a few microbial taxa are conserved across life stages of monarchs, the microbiome appears to be highly dynamic throughout the life cycle. Microbial diversity gradually diminishes throughout the larval instars, ultimately reaching its lowest point during the pupal stage and then recovering again in the adult stage. The microbial composition then undergoes a substantial shift upon the transition from pupa to adult, with female adults having significantly different microbial communities than the eggs that they lay, indicating limited evidence for vertical transmission of gut microbiota. While diet did not significantly impact overall microbial composition, our results suggest that fourth instar larvae exhibit higher microbial diversity when consuming milkweed with high concentrations of toxic cardenolide phytochemicals. This study underscores how diet and developmental stage collectively shape the monarch's gut microbiota.

Microbial dysbiosis is hypothesized to cause larval mass mortalities in New-Caledonian shrimp hatcheries. In order to confirm this hypothesis and allow further microbial comparisons, we studied the active prokaryotic communities of healthy Penaeus stylirostris larvae and their surrounding environment during the first 10 days of larval rearing. Using daily nutrient concentration quantitative analyses and spectrophotometric organic matter analyses, we highlighted a global eutrophication of the rearing environment. We also evidenced drastic bacterial community modifications in the water and the larvae samples using Illumina HiSeq sequencing of the V4 region of the 16S rRNA gene. We confirmed that Alteromonadales, Rhodobacterales, Flavobacteriales, Oceanospirillales and Vibrionales members formed the core bacteriota of shrimp larvae. We also identified, in the water and the larvae samples, several potential probiotic bacterial strains which could lead to rethink probiotic use in aquaculture (AEGEAN 169 marine group, OM27 clade, Ruegeria, Leisingera, Pseudoalteromonas and Roseobacter). Finally, investigating the existing correlations between the environmental factors and the major bacterial taxa of the water and the larvae samples, we suggested that deterministic and stochastic processes were involved in the assembly of prokaryotic communities during the larval rearing of P. stylirostris. Overall, our results showed that drastic changes mostly occurred during the zoea stages suggesting that this larval phase is crucial during shrimp larval development.

Microbial soil habitats are characterized by rapid shifts in substrate and nutrient availabilities, as well as chemical and physical parameters. One such parameter that can vary in soil is oxygen; thus, the microbial survival is dependent on adaptation to this substrate. To better understand the metabolic abilities and adaptive strategies to oxygen-deprived environments, we combined genomics with transcriptomics of a model organism, Acidobacterium capsulatum, to explore the effect of decreasing, environmentally relevant oxygen concentrations. The decrease from 10 to 0.1 µM oxygen (3.6 to 0.036 pO2% present atmospheric level, respectively) caused the upregulation of the transcription of genes involved in signal transduction mechanisms, energy production and conversion and secondary metabolites biosynthesis, transport and catabolism based on COG categories. Contrary to established observations for aerobic metabolism, key genes in oxidative stress response were significantly upregulated at lower oxygen concentrations, presumably due to a NADH/NAD+ redox ratio imbalance as the cells transitioned into nanoxia. Furthermore, A. capsulatum adapted to nanoxia by inducing a respiro-fermentative metabolism and rerouting fluxes of its central carbon and energy pathways to adapt to high NADH/NAD+ redox ratios. Our results reveal physiological features and metabolic capabilities that allowed A. capsulatum to adapt to oxygen-limited conditions, which could expand into other environmentally-relevant soil strains.

In this review, selected examples are presented to demonstrate how microfluidic approaches can be utilized for investigating microbial life from deep geological environments, both from practical and fundamental perspectives. Beginning with the definition of the deep underground biosphere and the conventional experimental techniques employed for these studies, the use of microfluidic systems for accessing critical parameters of deep life in geological environments at the microscale is subsequently addressed (high pressure, high temperature, low volume). Microfluidics can simulate a range of environmental conditions on a chip, enabling rapid and comprehensive studies of microbial behavior and interactions in subsurface ecosystems, such as simulations of porous systems, interactions among microbes/microbes/minerals, and gradient cultivation. Transparent microreactors allow real-time, noninvasive analysis of microbial activities (microscopy, Raman spectroscopy, FTIR microspectroscopy, etc.), providing detailed insights into biogeochemical processes and facilitating pore-scale analysis. Finally, the current challenges and opportunities to expand the use of microfluidic methodologies for studying and monitoring the deep biosphere in real time under deep underground conditions are discussed.

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 sub-tropical front (STF), the sub-Antarctic 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.

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 (HHRR, potential for human pathogens of acute resistance concern to acquire ARGs) from ecological resistome risk (ERR, 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 HHRR and ERR, 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.

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. C. 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.

The Southern green shield bug, Nezara viridula, is an invasive piercing and sucking pest insect that feeds on crops and poses a threat to global food production. Insects live in close relationships with microorganisms providing their host with unique capabilities, such as resistance to toxic plant metabolites. In this study, we investigated the resistance to and detoxification of the plant metabolite 3-nitropropionic acid by core and transient members of the N. viridula microbial community. Microbial community members showed a different tolerance to the toxin and we determined that six out of eight strains detoxified 3-nitropropionic acid. Additionally, we determined that 3-nitropropionic acid might interfere with the biosynthesis and transport of L-leucine. Moreover, our study explored the influence of diet on the gut microbial composition of N. viridula, demonstrating that switching to a single-plant diet shifts the abundance of core microbes. In line with this, testing pairwise microbial interactions revealed that core microbiota members support each other and repress the growth of transient microorganisms. With this work, we provide novel insights into the factors shaping the insect gut microbial communities and demonstrate that N. viridula harbours many toxin-degrading bacteria that could support its resistance to plant defences.

Despite covering less than 5% of Earth's terrestrial area, peatlands are crucial for global carbon storage and are hot spots of methane cycling. This study examined the dynamics of aerobic and anaerobic methane oxidation in two undisturbed peatlands: a fen and a spruce swamp forest. Using microcosm incubations, we investigated the effect of ammonium addition, at a level similar to current N pollution processes, on aerobic methane oxidation. Our findings revealed higher methane consumption rates in fen compared to swamp peat, but no effect of ammonium amendment on methane consumption was found. Members of Methylocystis and Methylocella were the predominant methanotrophs in both peatlands. Furthermore, we explored the role of ferric iron and sulfate as electron acceptors for the anaerobic oxidation of methane (AOM). AOM occurred without the addition of an external electron acceptor in the fen, but not in the swamp peat. AOM was stimulated by sulfate and ferric iron addition in the swamp peat and inhibited by ferric iron in the fen. Our findings suggest that aerobic methane oxidizers are not N-limited in these peatlands and that there is an intrinsic potential for AOM in these environments, partially facilitated by ferric iron and sulfate acting as electron acceptors.