ISME communications最新文献

Drying is threatening global river ecosystems due to climate change, altering community composition and function even upon flow resumption. This mesocosm study investigated the greenhouse gas emissions fluxes and underlying mechanisms from benthic habitats prone to 20-100 days of drying. Results show that CO₂ and N₂O emissions from biofilms did not increase when drying increased, due to the changes in functional communities and genes. Notable is the transformation of biofilm from carbon source to sink following prolonged drying (mean emission fluxes ranged from 804.78 to -305.55 mg m² h²). This was mainly due to strong increases in the abundance of genes involved in the Calvin-Benson-Bassham cycle (2.82 × 10^-5 to 7.12 × 10^-5), and functional taxa such as gemmatimonadota and pseudomonadota. These findings reveal a potential mitigation effect of drying on greenhouse gas emissions from rivers and streams, which could be relevant in the face of climate change.

Antimicrobial resistance (AMR) is a major health concern, and a range of antibiotic and non-antibiotic agents can select for AMR across a range of concentrations. Selection for AMR is often investigated using single compounds, however, in the natural environment and the human body, pharmaceuticals will be present as mixtures, including both non-antibiotic drugs (NADs), and antibiotics. Here, we assessed the effects of one of three NADs in combination with ciprofloxacin, a commonly used antibiotic that is often found at concentrations in global freshwaters sufficiently high to select for AMR. We used a combination of growth assays and qPCR to determine selective concentrations of mixtures and used metagenome sequencing to identify changes to the resistome and community composition. The addition of the three NADs to ciprofloxacin altered the selection dynamics for intI1 compared to the ciprofloxacin alone treatments, and sequencing indicated that mixtures showed a stronger selection for some AMR genes such as qnrB. The communities exposed to the mixtures also showed changed community compositions. These results demonstrate that NADs and ciprofloxacin are more selective than ciprofloxacin alone, and these mixtures can cause distinct changes to the community composition. This indicates that future work should consider combinations of antibiotics and NADs as drivers of AMR when considering its maintenance and acquisition.

Understanding the long-term persistence of human-associated microbial signatures in burial soils offers a untapped insights into historical human health, decomposition, and ecological transformation. This study investigates whether centuries-old burial soils retain distinguishable microbial evidence of human decomposition using 16S rRNA gene sequencing on 81 samples from the New York African Burial Ground (NYABG), a 17th and 18th century cemetery for free and enslaved Africans. Comparative analyses against six control soils from nearby urban parks were conducted using QIIME2, ALDEx2, and ANCOM. Burial soils exhibited significantly greater alpha diversity (Faith's PD, Shannon, observed ASVs; P < .01) and distinct beta diversity patterns (Bray-Curtis, UniFrac; PERMANOVA P = .001). Enrichment of Firmicutes, Actinobacteriota, and gut-associated genera such as Bacillus and Ruminococcus characterized burial soils, whereas oligotrophic taxa dominated controls. Tentative identifications of human-associated pathogenic genera (e.g. Fusobacterium periodonticum, Prevotella pleuritidis) were observed exclusively in burial soils, suggesting their origin from the interred individuals but requiring further validation. These findings demonstrate that soil microbiomes reflect host-associated microbial communities long after decomposition, providing a scalable, nondestructive approach for reconstructing ancient microbial communities and host-associated health signatures. This work establishes the NYABG burial soil microbiome as a valuable model for microbial archaeology and introduces a replicable framework for integrating environmental microbiology, bioarchaeology, and historical epidemiology through the lens of postmortem microbial ecology.

Estuaries are highly productive ecosystems where microbial communities drive nutrient and carbon cycling, supporting complex food webs. With intensifying anthropogenic pressures, it is critical to understand the capacity of these communities to maintain essential functions under environmental change. Here, we examined the metabolic functions and redundancy in the microbial community of San Francisco Bay (SFB) sediments, providing the first large-scale, genome-resolved, and spatiotemporally resolved characterization of the estuary. Salinity, iron, phosphorus, sulfur, and total sediment nitrogen were significantly correlated with microbial community composition, suggesting these factors play a key role in structuring SFB communities. In support of this, we identified broad capabilities for iron cycling and key uncultured players that contribute to denitrification, nitrification, and complete nitrification (comammox). We also identified widespread capabilities for sulfur cycling, including understudied lineages capable of rDsr-mediated sulfur oxidation. SFB MAGs exhibited partitioning of multistep metabolisms, or metabolic handoffs, and the rare biosphere broadly encoded key nitrogen and sulfur cycling genes. Despite shifts in community composition across sites and fluctuations in environmental parameters, key nitrogen and sulfur metabolisms were maintained throughout the estuary, especially in nitrate reduction, nitrite reduction, and the Dsr/Sox pathway. The presence of multiple microbial taxa with similar functional roles (functional redundancy) may provide an ecosystem buffer, suggesting these functions could better recover from disturbances and ultimately contribute to the long-term health and sustainability of these vital coastal habitats.

The gut microbiota functions as a complex adaptive system where microbes form structural modules known as "guilds." Each guild comprises taxonomically distinct microbes that work together as cohesive functional units, contributing to overall system function. Traditional taxon-based microbiome analyses often yield inconsistent associations with disease, limiting mechanistic insights. To address this, we compared guild-based and taxon-based approaches using datasets from a time-restricted feeding (TRF) study in mice. C57BL/6 J male mice were assigned to ad libitum feeding or TRF groups, with metabolic parameters and gut microbiota composition assessed over 12 weeks. Isocaloric TRF improved glucose tolerance and reduced weight gain in high-fat diet (HFD)-fed mice while maintaining metabolic stability in normal-fat diet-fed mice. To examine microbial contributions, 293 prevalent amplicon sequence variants (ASVs) from the 16S rRNA gene's V3-V4 regions were clustered into 34 co-abundance groups (CAGs), representing potential microbial guilds and accounting for 96% of the total sequence abundance. By contrast, the taxon-based approach classified 660 ASVs into 126 genera, capturing only 78% of the total sequence abundance while omitting 22% of sequences representing novel microbes. The 34 CAGs preserved community-level information more effectively than the 66 prevalent genera, as demonstrated by Procrustes analysis. Five CAGs correlated with improved metabolic phenotype under TRF, including unclassifiable ASVs. Notably, two key CAGs exhibited conserved diurnal rhythmicity under TRF. In contrast, ASVs within putative health-relevant genera displayed opposing TRF responses. This study underscores microbial guilds as key mediators of TRF's metabolic benefits and emphasizes the need to recalibrate taxon-based microbiome analysis biomarker discovery.

Phaeobacter are marine alphaprotebacteria capable of producing a potent antibacterial compound, tropodithietic acid. Here we demonstrate that they are part of the microbiome of marine bryozoans where they during warmer months reach 10⁵ CFU/g. The levels exhibited a bimodal fluctuation, in both bryozoans and seawater across seasons. However, the population of Phaeobacter sp. was already established in the bryozoans prior to the peak in seawater and did not accumulate as a function of filter feeding on phytoplankton biomass, suggesting that the seawater population is likely seeded from the bryozoan-associated Phaeobacter sp. population rather than the opposite. By comparing whole-genome sequences of more than 100 bryozoan-associated Phaeobacter isolates sampled over a 12-year period, we found that all belonged to the same novel species and no systematic genetic changes occurred within it over the 12 year sampling period despite the fact that the population oscillated from below the limit of detection and across five orders of magnitude to 5.2 Log₁₀ CFU g^-1 bryozoan within individual years and hence were subject to drift. All isolates had the genetic capacity to produce tropodithietic acid (TDA) and the algicidal compounds, roseobacticides. The genes encoding the enzymes for TDA biosynthesis remained stable over time, indicating a conserved phenotype important in the ecophysiology of the bacteria. TDA biosynthetic genes were actively transcribed within the bryozoan host further corroborating the notion that the secondary metabolites of this novel host-associated Phaeobacter sp. may be central to its role within the bryozoan microbiome.

The deep biosphere encompasses life beneath the Earth's surface and constitutes a substantial portion of the planet's microbial biomass. This study analyzed nucleic acid datasets from low-carbon and low-energy deep terrestrial subsurface groundwaters across four continents and revealed four core global populations. These populations exhibited metabolic strategies and adaptations reflecting depth and environmental constraints. Erythrobacter featured heterotrophic metabolism; Thiobacillus demonstrated sulfur oxidation coupled to denitrification along with carbon and nitrogen fixation; Methanobacteriaceae were methanogenic autotrophs using the Wood-Ljungdahl pathway (WL); and Candidatus Desulforudis audaxviator functioned as a sulfate-reducer also encoding the WL pathway. Depth-related adaptations suggested heterotrophic dominance at shallower depths with increasing contributions from autotrophy with depth. Finally, comparative genomics revealed minimal evolutionary changes among these populations, suggesting functional conservation since diverging from their ancestral lineages. These findings underscore a global deep biosphere core community.

A major barrier for most fungal species to infect humans is their inability to grow at body temperature (37°C). Global warming and more frequent extreme heat events may impose selection pressures that allow fungal adaptation to higher temperatures. As fungi adapt to warmer environments, they may overcome the thermal barrier that limits infection of warm-blooded hosts, including humans. Cities are heat islands that are up to 8°C warmer than their suburban counterparts and may thus be an important reservoir of thermotolerant fungi that inhabit environments near humans. Here, we describe a novel and inexpensive technique to collect fungal samples from various sites in Baltimore, MD using commercially available taffy candy. Our results show that fungal isolates from warmer neighborhoods show greater thermotolerance and lighter pigmentation relative to isolates of the same species from cooler neighborhoods, suggesting local adaptation. Lighter pigmentation in fungal isolates from warmer areas is consistent with known mechanisms of pigment regulation that modulate fungal temperature. The opportunistic pathogen Rhodotorula mucilaginosa from warmer neighborhoods had a higher resistance to gradual exposure to extreme heat than those from cooler neighborhoods. Our results imply fungal adaptation to increased temperatures in warmer areas of cities. The acquisition of thermotolerance poses a potential risk for humans, as it is necessary for fungal survival within humans.

Food webs govern interactions among organisms and drive energy fluxes within ecosystems. With an increasing appreciation for the role of symbiotic microbes in host metabolism and development, it is imperative to understand the extent to which microbes conform to, and potentially influence, canonical food web efficiencies and structures. Here, we investigate whether bacteria and their taxa and functional genes are compositionally nested within a simple model food web hierarchy, and the extent to which this is predicted by the trophic position of the host. Using shotgun and amplicon sequencing of discrete food web compartments within replicate tank bromeliads, we find that both taxonomy and function are compositionally nested and largely mirror the pyramid-shaped distribution of food webs. Further, nearly the entirety of bacterial taxa and functional genes associated with hosts are contained within host-independent environmental samples. Community composition of bacterial taxa did not significantly correlate with that of functional genes, indicating a high likelihood of functional redundancy. Whereas bacterial taxa were shaped by both location and trophic position of their host, functional genes were not spatially structured. Our work illustrates the advantages of applying food web ecology to predict patterns of overlapping microbiome composition among unrelated hosts and distinct habitats. Because bacterial symbionts are critical components of host metabolic potential, this result raises important questions about whether bacterial consortia are shaped by the same energetic constraints as hosts, and whether they play an active role in food web efficiency.

Understanding the spatial dynamics of plant-associated microbial communities is increasingly urgent in the context of habitat loss and the biodiversity crisis. However, the influence of reduced habitat size and connectivity on the assembly mechanisms underlying microbial associations is fundamental to advancing microbial ecology and conservation. In the Brazilian Amazon, we investigated nitrogen-fixing (diazotrophic) bacterial communities associated with two epiphyllous liverworts, Cololejeunea surinamensis and Radula flaccida, across 11 forest sites within the Biological Dynamics of Forest Fragments Project landscape. Using amplicon sequencing targeting the nitrogenase gene (nifH), we characterized diazotroph community diversity, inferred assembly mechanisms through null models, and analyzed co-occurrence network structure. Host-specific associations were evident: C. surinamensis predominantly hosted Hassallia, while R. flaccida was primarily associated with Fischerella. Despite habitat fragmentation, diazotrophic richness and composition remained similar across habitats of different sizes, consistent with strong homogenizing dispersal. Network analyses revealed that smaller fragments harbored more modular communities with fewer module hubs, pronounced shifts in key species relative abundance, and reduced network robustness. Our findings underscore the influence of habitat size on the stability of liverwort-associated diazotrophs, with smaller fragments exhibiting lower key species specificity and disruption of microbe-microbe interactions. Our results emphasize the importance of conserving large, connected forest habitats to maintain the functional integrity of phyllosphere N-fixing microbiota.