Microbial Ecology最新文献

Complete ammonia oxidizers (comammox), oxidizing ammonia to nitrate directly, have been found to exist widely in multiple environments, but their distribution patterns are still under-explored in Antarctic environments. For the first time, the sediments were collected from West Antarctic lakes to investigate distribution patterns and community structure for comammox, ammonia oxidizing archaea (AOA) and bacteria (AOB), and nitrite-oxidizing bacteria (NOB), as well as the associations between ammonia oxidizers and antibiotic resistance genes (ARGs). Comammox clade B and AOB were dominant ammonia oxidizers, with the abundances of (1.62 ± 0.10) × 10² - (5.21 ± 0.74) × 10⁶ and (0.17 ± 0.05) × 10⁵ - (4.79 ± 0.65) × 10⁵ copies g^- 1 sediment, respectively. Comammox clade B, instead of clade A, occurred in all sediments, exhibiting higher abundances than AOB and AOA in most of the sediments. The abundances for comammox clade B demonstrated significant positive correlation (p < 0.01) with NH₄⁺-N levels, but negative correlation (p < 0.05) with C: N ratios. The coexistence of ammonia oxidizers in lake sediments was jointly structured by niche differentiation and environmental variables, and pH, modulated by penguin guano input, was found to be the most crucial factor in shaping their community structure. Co-occurrence network analyses revealed strong synergistic interactions between comammox and AOB, AOA, NOB, which played a critical role in nitrification processes. Our results further confirmed that comammox could act as important hosts for ARGs, hence stimulated their transmission and proliferation in the sediments. This study presented novel insights into the distribution patterns for ammonia oxidizers, their niche differentiation and the associations with ARGs in natural lake sediments of West Antarctica.

Phyllosphere microorganisms play a vital role in supporting host plant health and adaptability. Although previous research on the effects of host performance and their phylogenetic associations on phyllosphere microbial communities has predominantly focused on tropical, subtropical, and temperate forestry ecosystems, the responses of these microbial communities to plant phylogeny and functional traits in temperate desert environments remains poorly understood. In this study, we conducted a quantitative analysis of bacterial and fungal community structures in the phyllosphere of 39 plant species from the Gurbantunggut Desert, a typical temperate desert in Central Asia. Variation partitioning analysis revealed that plant phylogeny, leaf physicochemical properties, and leaf morphological characteristics collectively explained the variation in phyllosphere microbial communities. Specifically, these factors accounted for 19.26%, 14.53%, and 2.32% of the variance in bacterial communities, and 11.55%, 8.36%, and 2.19% of the variance in fungal communities, respectively. A significant hierarchical pattern emerged: plant phylogeny > leaf physicochemical properties > leaf morphological characteristics, highlighting the dominant role of plant filtering effects in community assembly. Linear mixed-effects model analysis further confirmed the significant influence of multiple plant attributes, including phylogeny and functional traits, on microbial community structure. Plant-microbe interaction analysis revealed distinct host preferences of microbial taxa across different plant taxonomic levels. Co-evolutionary analysis also indicated a significant phylogenetic association between host plants and their phyllosphere amplicon sequence variants (ASVs). Overall, our findings demonstrate that plant attributes, particularly plant phylogeny and functional traits, are key factors driving the assembly of phyllosphere microbial communities in deserts. This study provides new insights into species coexistence mechanisms in fragile habitats and enhances our understanding of plant-microbe interactions in global desert ecosystem.

Intercropping is a prevalent soil management strategy within walnut orchards, while its impacts on the functionality of arbuscular mycorrhizal fungi (AMF) in walnuts (Juglans regia) remain unclear, especially concerning soil carbon (C) sequestration via glomalin-related soil protein (GRSP). This study aimed to explore the effects of inoculation with the AMF species Diversispora spurca and intercropping with hairy vetch (Vicia villosa) on walnut biomass accumulation, soil water-stable aggregate (WSA) stability, leaf and root C (C_leaf and C_root) content, soil organic carbon (SOC), GRSP, and GRSP-contained C (C_GRSP), in addition to the contribution rate of C_GRSP to SOC. The intercropping treatment significantly inhibited root mycorrhizal colonization rate, soil hyphal length, and spore density in AMF-inoculated walnut plants. Individual AMF inoculation, rather than individual intercropping, significantly promoted shoot and root biomass accumulation, WSA stability, SOC, C_leaf and C_root, the levels of purified easily extractable (EEG), difficultly extractable (DEG), and total GRSP (TG), as well as their C contents. The combination treatment (AMF inoculation + intercropping) displayed limited benefits, improving just WSA stability without yielding synergistic advantages over individual treatments. Arbuscular mycorrhizal fungal inoculation significantly increased C_GRSP, especially C_DEG, while individual intercropping resulted in a reduction of C_DEG. The combination treatment elevated both C_DEG and C_TG, albeit to a lesser extent than AMF alone. The contribution rates of C_EEG, C_DEG, and C_TG to SOC were 0.33% - 0.53%, 1.16% - 1.78%, and 1.49% - 2.31%, respectively. Although AMF inoculation significantly increased the contribution rates of C_DEG and C_TG to SOC, this effect was diminished when combined with intercropping. Notably, C_DEG, rather than C_EEG, exhibited a significantly positive correlation with SOC and WSA stability. The findings provide new insights into the mechanisms of SOC sequestration in walnuts grown in controlled environments and offer a theoretical basis for the application of AMF in walnut cultivation.

Antibiotic resistance genes (ARGs) accumulate in aquatic environments, where they create reservoirs and transmission pathways that can undermine antimicrobial treatments and alter the microbial community structure in ways that ultimately affect human and animal health. However, the contribution of zooplankton in these pathways remains critically overlooked. Emerging evidence shows that compared with surrounding water, copepods and cladocerans accumulate ARG loads that are one to two orders of magnitude greater, acting as microbial hotspots that disperse resistant bacteria across seasons and depths. Inside protistan vacuoles, densely packed prey cells undergo conjugation, rapidly accelerating horizontal ARG transfer. Long-term archives reveal persistent ocean-wide dissemination of the class-1 integron integrase (intI1) and sul2 genes since at least the 1970s. Here, I synthesize mechanistic and field evidence, pinpoint knowledge gaps, and recommend priorities: integrate zooplankton into routine ARG surveillance, quantify biofilm-mediated exchanges, and mitigate contamination from coselective pollutants to curb zooplankton-driven ARG propagation. By framing zooplankton-associated ARG dynamics within the broader community ecology of antimicrobial resistance, this mini-review highlights how aquatic food-web processes feed back into the emergence, evolution, and transmission of resistance that concerns for One Health outcomes beyond the clinic.

The rapid expansion of tunnel engineering in China has led to extensive excavation of gravelly soils, resulting in significant land occupation that threatens the ecological environment and surrounding biota. As a result, there is an increasing need for effective ecological restoration of nutrient-poor gravelly soils, where challenges in vegetation establishment and sustainable soil management persist. This study evaluates the potential of Bacillus subtilis to promote the growth of Festuca arundinacea in engineered gravel soils through a controlled greenhouse experiment, examining its effects on plant growth, soil nutrient dynamics, and microbial community structure. The results showed that, compared to the control group (CK), neither the Bacillus subtilis treatment group (Bs) nor the nutrient application treatment group (LB) significantly altered the soil bacterial species composition at the phylum level. However, at the genus level, Azotobacter dominated the LB group, while Sphingomonas was the predominant genus in both the CK and Bs groups. Additionally, Bacillus subtilis significantly increased bacterial diversity relative to the nutrient application treatment, leading to substantial changes in microbial community composition. Furthermore, Bacillus subtilis notably enhanced both aboveground and belowground biomass, improved nutrient uptake, and increased the availability of phosphorus and potassium. It also stimulated soil enzymatic activities involved in carbon, nitrogen, and phosphorus cycling, emphasizing its critical role in nutrient cycling. Thus, Bacillus subtilis-driven soil enhancement offers a promising solution for ecological restoration in nutrient-poor gravelly soils, where conventional amendments are often ineffective. These findings underscore the potential of microbial-plant synergies to improve soil fertility and support sustainable vegetation restoration.

Acid mine drainage (AMD) generated during coal mining activities is characterized by low pH, high concentrations of dissolved metals and metalloids, and elevated sulfate levels, all of which significantly impact surrounding ecosystems. Scaling up biochemical passive reactor (BPR) systems represents a promising approach for the in situ bioremediation of AMD. While numerous laboratory-scale studies have described the taxonomic and functional composition of microbial communities in BPRs, typically dominated by (ligno)cellulolytic organisms and sulfate-reducing bacteria (SRB), it remains unclear whether this composition is maintained at the field-pilot scale under environmental conditions. To address this gap, 16S rRNA gene metabarcoding and shotgun metagenomics analyses were performed to characterize the taxonomic and functional diversity of microbial communities in the BPRs within a multi-unit field-pilot system. The results revealed that bioremediation effectiveness was driven by syntrophic interactions among hydrolytic, fermentative, and sulfate-reducing bacteria, aligning with laboratory-scale observations. While community composition shifts altered specific taxa, core operational dynamics remained preserved.

Soil fatigue, well documented in various crops, presents a significant challenge to banana production by causing fast and then gradual declines in plant growth and yield over years of cultivation. Despite its impact on profitability, the underlying mechanisms driving soil fatigue remain poorly understood; however, a strong link to shifts in the soil microbiome has been suggested. We investigated the dynamics of microbial communities in relation to soil fatigue, using a novel semi-controlled outdoor experimental system. Soil at different stages of fatigue (0 to 42 months of banana cultivation) was generated in large containers filled with initially healthy soil. Banana plants grown in these soils were replaced with new plants which showed soil age-dependent growth. Three months postplanting, soil and root samples were collected for analyses of soil parameters and microbial community composition using bacterial (16S) and fungal (ITS) amplicon sequencing. We identified minor age-related shifts in mainly pH, potassium, and organic matter in the soil. While alpha diversity remained unchanged, significant shifts in bacterial and fungal community composition were observed in fatigued soils. Notably, the relative abundance of bacterial families such as Flavobacteriaceae, Pseudomonaceae, and Acidibacter increased, as did some fungal taxa (many from groups with known pathogens)-Ceratobasidiaceae (including Rhizoctonia), Dothideomycetes, and Stachybotryaceae. Simultaneously, the relative abundance of bacterial families with known beneficial members, including Gemmatimonadaceae, Moraxellaceae, Sphingomonadaceae, and Azospirillaceae, as well as symbiotic fungal taxa such as Glomeraceae and Lasiosphaeriaceae, declined. Thus, soil fatigue may be correlated to the proliferation of pathogenic populations and a loss of beneficial microorganisms.

Cycads are ancient gymnosperms that play a crucial role in the soil health of scarp forests through their symbiotic associations with nutrient-cycling bacteria. However, the abundance of cycads in scarp forests has been decreasing at an alarming rate, highlighting the importance of determining the role of these species in nutrient cycling, microbial dynamics, and soil health. This study examined soil nutrient and microbial dynamics associated with Encephalartos villosus across four scarp forest sites in KwaZulu-Natal, South Africa. Soil samples were collected from the rhizosphere and non-rhizosphere zones (3-5 m away from the canopy) of mature plants. Results show that collection point did not influence soil nutrient and properties statistically; however, site-level variation was evident, with Hlathikhulu showing higher pH and nutrient concentrations, while Vernon Crookes exhibited lower pH and nutrient availability. Rhizosphere soils supported a greater diversity of nutrient-cycling bacteria, particularly taxa from the genera Bacillus, Burkholderia, Enterobacter, Luteibacter, and Pseudomonas with N-fixing, P-solubilizing, and N-cycling functions. Non-metric multidimensional scaling (NMDS) revealed that site differences, mainly driven by Mg, Ca, K, Zn, pH, and total cations, were stronger predictors of soil nutrient and microbial community variation than collection point alone. Enzyme assays showed that glucosaminidase and acid phosphatase were associated with community differences. These findings indicate that E. villosus enhances soil nutrient enrichment and microbial functional diversity in scarp forests, although the strength of these effects depends on local site conditions. Conservation of E. villosus is therefore critical, not only for species survival but also for sustaining soil fertility and ecosystem functioning in nutrient-limited scarp forest habitats.

The role of gut microbiota in shaping host fitness is already well established. However, it remains unclear to what extent the gut microbiota influences host fitness in the presence of environmental stressors. Here, we tested the hypothesis that responses of water flea Daphnia to the heavy metal nickel are mediated by gut microbiota. Germ-free D. magna exhibited somewhat lower fitness than did those with gut microbiota transplant. Among germ-free Daphnia, those that were exposed to heavy metals did not differ in fitness from unexposed Daphnia. In contrast, when incubated with their donors' gut microbiota, initially germ-free D. magna continuously exposed to nickel for 21 days showed a significantly lower survival rate than those not exposed to nickel. We detected a reduced set of microbes in the formerly germ-free Daphnia in the presence of nickel. Transcriptomic analysis of Daphnia showed that expression/regulation of genes related to oxygen transport, chitin metabolism, and detoxification changed in response to the reduced gut microbiomes acquired in the presence of nickel. Our findings show that the toxic effects of heavy metal led to a reduced diversity of gut microbiota in Daphnia and can thus affect host fitness.

Heat stress poses a significant global challenge to sustainable livestock production, leading to detrimental impacts on animal production and welfare. Reduced appetite and increased body temperature further disrupt the gastrointestinal microbial ecosystem of heat-stressed animals, altering nutrient digestion and affecting host production. However, reported heat-stress-associated microbes have varied across studies, partly due to inconsistencies in microbiota analysis pipelines and taxonomic levels reported. In this study, to identify consistent rumen microbial taxa influenced by heat stress and evaluate potential of rumen microbiota in heat stress prediction, we collected publicly available raw 16S rRNA gene amplicon sequencing data of rumen fluid samples from lactating Holstein cattle housed in thermoneutral or heat stress condition from eight studies, analyzed their microbial composition using a consistent bioinformatic pipeline, and built machine learning models with the rumen microbiota profile to predict heat stress. Important rumen microbial taxa were selected using Boruta (a feature selection algorithm to identify important features) as potential biomarkers to predict heat stress, such as lactate-producing bacteria Lactobacillales, fiber-degrading bacteria Ruminococcaceae UCG-001, and methanogenic archaea Methanomicrobium. Additionally, the random forest model using the available animal factors and relative abundance of rumen microbial taxa showed a much higher performance for heat stress prediction, compared to the model without rumen microbiota profile (Area Under the Curve: 0.851 vs. 0.440). This study confirmed a distinct rumen microbiota signature in heat-stressed lactating Holstein cattle and identified specific rumen microbial taxa as potential biomarkers that could be targeted to mitigate heat-stress responses in dairy cows.