FEMS microbiology ecology最新文献

The globally distributed genus Methylobacter plays a crucial role in mitigating methane emissions from diverse ecosystems, including freshwater and marine habitats, wetlands, soils, sediments, groundwater, and landfills. Despite their frequent presence and abundance in these systems, we still know little about the genomic adaptations that they exhibit. Here, we used a collection of 97 genomes and metagenome-assembled genomes to ecogenomically characterize the genus. Our analyses suggest that the genus Methylobacter may contain more species than previously thought, with >30 putative species clusters. Some species clusters shared >98.65% sequence identity of the full-length 16S rRNA gene, demonstrating the need for genome-resolved species delineation. The ecogenomic differences between Methylobacter spp. include various combinations of methane monooxygenases, multigene loci for alternative dissimilatory metabolisms related to hydrogen, sulfur cycling, and denitrification, as well as other lifestyle-associated functions. Additionally, we describe and tentatively name the two new Methylobacter species, which we recently cultured from sediment of a temperate eutrophic fishpond, as Methylobacter methanoversatilis, sp. nov. and Methylobacter spei, sp. nov. Overall, our study highlights previously unrecognized species diversity within the genus Methylobacter, their diverse metabolic potential, versatility, as well as the presence of distinct genomic adaptations for thriving in various environments.

The gut microbiome of preterm infants is highly vulnerable to perturbations. Members of the class Clostridia are among the first anaerobes colonizing the preterm gut, yet their ecological roles and antimicrobial resistance (AMR) properties remain poorly understood. We characterized 98 Clostridia isolates from fecal samples of preterm infants, spanning 17 species and 11 genera. Isolates were identified by MALDI-TOF and 16S rRNA sequencing, colonization levels were quantified, and antimicrobial susceptibility was assessed by disk diffusion and E-test. Resistance determinants were screened by PCR and sequenced. We focused on Clostridia that were present at low colonization levels (mean 5.3 log10 CFU g-1 of feces). While most isolates were susceptible to amoxicillin-clavulanic acid, imipenem, and metronidazole, resistance to tetracycline (12%), clindamycin (35%), and cefotaxime (35%) was observed. Distinct species-specific resistance included linezolid (Clostridium argentinense), chloramphenicol (Clostridium innocuum), and tigecycline (Paeniclostridium sordellii), and one Robinsonella peoriensis isolate displayed vancomycin resistance. The detection of tet and erm genes corresponded with phenotypic resistance, while β-lactamase activity was uncommon. Although colonizing at low levels, these findings highlight the ecological significance of rarely studied commensal Clostridia and their contribution to the neonatal resistome, acting as underappreciated reservoirs of AMR genes during a critical window of microbiome assembly.

The human gastrointestinal (GI) ecosystem is a highly dynamic environment and provides diverse microbial habitats for the gut microbiota, which are shaped by environmental factors, metabolic processes, and immune responses. The host-microbiota interactions in the gut form a balanced yet adaptable network. When invading microorganisms enter the GI tract, they deploy multiple strategies to overcome both host defences and competition from the resident microbiota. In turn, the host and native microbiota have evolved sophisticated mechanisms to prevent the colonization of invading organisms, collectively termed colonization resistance. Deciphering the mechanisms of interplay in the host‒microbe and microbe‒microbe relationships in the gut offers crucial insights into therapeutic interventions aimed at restoring or maintaining gut microbial homeostasis.

The biomass, pH changes, and chemotaxis of Enterobacter cloacae (E. cloacae) DJ strain were assessed under various conditions using liquid culture and semi-solid agar plate. Concurrently, GABA concentration, GAD activity, and chemotactic gene expression were measured. The results demonstrated that DJ strain exhibited adaptability to saline-alkaline environments. After 4 h of culture, the pH value decreased, with more pronounced pH changes observed in the saline-alkaline groups. Semi-solid agar plate assays revealed that the DJ strain exhibited the strongest chemotaxis toward the saline-alkaline environment. The average migration radius of the DJ strain reached 1.64 ± 0.09 cm in the saline-alkaline environment after a 24-h cultivation, significantly exceeding the control group's value of 0.88 ± 0.097 cm. The DJ strain exhibited strong positive taxis toward the saline-alkaline environment. Na+ concentration was identified as the primary factor influencing the chemotactic behavior of DJ strain. The GABA content in the saline-alkali group and salt group was 13±0.38 µmol/l and 10.5±1.12 µmol/l, respectively. GAD enzyme activity peaked after 4 h of cultivation, then decreased progressively. qPCR results indicated that the expression of tsr and che-Y genes was up-regulated under saline-alkaline conditions. We propose a model whereby environmental Na+ activates GAD enzyme activity in the DJ strain, leading to increased GABA production that alters the bacterial microenvironment. In response, the DJ strain up-regulates chemotaxis-related gene expression, thereby modifying its behavior to adapt to the saline-alkaline environment.

The secreted mucus layer in the human gastrointestinal tract constitutes both a protective boundary between gut lumen and epithelium as well as an important nutrient source for members of the gut microbiota. While many gut microbes possess the genetic potential to degrade mucin, it is still unclear which species transcribe the respective genes. Here, we systematically analysed publicly available metagenome and metatranscriptome datasets to characterize the gut microbial community involved in mucosal glycan degradation. We utilized cooccurrence network analysis and linear regression to elucidate the ecological strategies of, and relationship between, mucus degraders. We found that although ~60% of species carrying genes encoding for mucosal-glycan-degrading enzymes have detectable transcription of these genes, only 21 species prevalently transcribe more than 1 gene. Furthermore, the transcription of individual genes was frequently dominated by single species in individual samples. Transcription patterns suggested the presence of competitive mucosal glycan degraders characterized by abundance-driven transcription that were negative predictors for the transcription of other degraders as well as opportunistic species with decoupled abundance and transcription profiles. These findings provide insights into the ecology of the mucosal glycan degradation niche in the human gut microbiota.

Climate is a major determinant of fungal diversity on both large and small spatial scales. However, little is known about the combined effects of regional temperature, microclimate, and dispersal vectors on fungal diversity. We studied the effect of microclimate and wood-inhabiting beetles serving as potential dispersal vectors on the diversity of wood-inhabiting fungi in general-and of brown- and white-rot fungi in particular-along a regional temperature gradient. This focus is motivated by the critical role that different rot types play in wood decomposition and carbon cycling. Beetle and fungal communities were sampled in 243 logs of Norway spruce (Picea abies), which were placed along a 1200 km latitudinal gradient in Sweden (i.e. regional temperature gradient) and under different shading conditions (i.e. microclimatic gradient). Species richness of brown-rot fungi increased with beetle abundance in both the south and the north, whereas shade level markedly limited their species richness only in the north. In contrast, white-rot fungi were unaffected by either factor. These findings highlight that fungal responses to microclimate and dispersal vectors may differ between regions and suggest that species richness of brown-rot fungi may increase with a warming climate, especially in the north.

Thermal stratification drivers of microbial community organization and functional potential in deep lakes, yet comparative analyses of epilimnetic and hypolimnetic microbiome dynamics remain limited. In this study, we combined 16S rRNA gene sequencing with functional microarray (GeoChip 5.0) to investigate stratification-induced shifts in microbial community composition and functional structure in Lake Fuxian, a deep monomictic plateau lake in Yunnan Province, Southwest China. Our analyses revealed a partial decoupling between taxonomic and functional diversity across water layers: the oxygen-depleted hypolimnion harbored higher bacterial taxonomic richness and distinct taxa (Nitrospirae, Parcubacteria, and Thaumarchaeota), whereas the epilimnion exhibited greater functional gene richness with lower beta diversity, indicating enhanced metabolic flexibility. Molecular ecological network analysis uncovered contrasting interaction patterns, with hypolimnetic communities exhibiting greater complexity and modularity. Notably, the Chloroflexi-associated amyA gene emerged as a module hub in hypolimnetic functional molecular ecological networks while distinct connector taxa characterized both epilimnetic and hypolimnetic species molecular ecological networks. Multivariate analyses identified dissolved oxygen and nutrient availability as key environmental drivers of vertical microbial stratification. These findings elucidate microbial adaptation to stratified conditions and underscore the distinct roles of epilimnetic and hypolimnetic communities in biogeochemical cycling in deep lakes experiencing climate-mediated thermal regime shifts.

The High Arctic deserts of remote northern Greenland are expected to become warmer and wetter due to climate change. Precipitation changes will increase fluctuations in surface soil salinity, and the same happens for thawed permafrost soil where stable salt concentrations are replaced with fluctuating salinity during annual freeze-thaw cycles. Both have unknown effects on the microbial communities and their emissions of microbial volatile organic compounds (MVOCs). These compounds are produced from various pathways mainly as secondary metabolites and have ecological and climatic implications when released into the environment and the atmosphere. Thus, it is important to explore the effects of environmental changes, such as changes in salinity, on soil microbial communities and their MVOC emissions. Here, we characterize the MVOC production of three novel bacterial isolates from northern Greenland throughout their growth period under low, moderate, and high salt concentrations. We demonstrate that salinity significantly alters both the quantity and composition of MVOCs emitted by all three strains, including changes in the emissions of sulphur- and nitrogen-containing compounds, potentially leading to ecosystem nutrient loss. The observed changes in MVOC profiles suggest that changes in soil salinity due to climate change could alter microbial metabolism and MVOC emissions, with potential implications for Arctic nutrient cycling and atmospheric chemistry.

Pseudomonadota (formerly Proteobacteria) commonly use a contact independent cell-cell communication system known as quorum sensing (QS) mediated by N-acyl-homoserine lactone (AHL) signal molecules. The canonical AHL QS system involves a luxI-family gene, which encodes an AHL synthase, and a luxR-family gene, which encodes a transcriptional regulator responsive to the cognate AHL(s). This study involves the AHL QS system of Enterobacter asburiae AG129, a root associated strain isolated from rice (Oryza sativa). Enterobacter asburiae AG129 produces the N-butanoyl homoserine lactone (C4-AHL) signal molecule. Genome sequencing of strain AG129 revealed the presence of a canonical AHL QS system, comprising genetically adjacent easI-like and easR-like genes. A genomic easI knockout mutant was no longer able to produce AHLs, but the in-trans complementation with a plasmid carrying the easI gene restored the AHL production. QS mediated by AHLs in AG129 was found to influence rice root colonization, and secretome analysis highlighted a significant regulatory role in the expression of Type VI secretion system (T6SS) proteins. Gas chromatography-mass spectrometry analysis identified 16 volatile organic compounds (VOCs) that were more abundantly emitted by the wild-type strain compared to the easI mutant. Overall, our findings suggest that AHL-based QS in E. asburiae AG129 positively regulates T6SS expression and VOC production, while negatively affecting root colonization and motility. This study is among the first to explore the role of QS signaling in a bacterial root-endophyte, providing evidence of a connection between QS activity and the ability of the bacterium to inhabit, compete and colonize the plant root endosphere.

Subsurface microbiology is at a crossroads, evolving from asking 'who's home' to seeking clarity on microbes' functionality and the key processes that constrain subsurface life. Importantly, the processes subsurface microorganisms mediate are central to societal needs to mitigate climate change and address waste storage, as proposed solutions to both involve subsurface habitats. However, subsurface sampling opportunities and funding remain limited and, in some cases, have diminished. This perspective article is aimed at scientists who have or might develop an interest in the geomicrobiology of the subsurface, for funding agencies worldwide, and for scientists and engineers engaged in the extractive and waste disposal industries. It briefly reviews subsurface science's history and current status and proposes some actions for moving forward. In particular, we see the continued need for engaging early-career microbiologists in drilling projects, increasing access through industry partnerships, microbiology-led drilling projects, and creating interdisciplinary drilling projects by including microbiologists during the drilling project planning.