Vegetation restoration in an alpine meadow: Insights from soil microbial communities and resource limitation across soil depth.

Aboveground vegetation restoration shapes the soil microbial community structure and affects microbial resource acquisition. However, the changes in soil microbial resource limitation in subsoil during vegetation restoration are still unclear. In this study, the microbial community structure and resource limitation in an alpine meadow soil profile that had undergone natural restoration for short-term (4-year) and long-term (10-year) restoration in response to vegetation restoration were explored through high-throughput sequencing analysis and extracellular enzyme stoichiometry (EES). There was no significant difference in microbial composition and α diversity between short- and long-term restoration soils. Soil microorganisms in this alpine meadow were mainly limited by phosphorus. Carbon limitation of soil microorganisms was significantly decreased in each layer (0-15, 15-30, 30-45, 45-60, and 60-80 cm corresponding to L1, L2, L3, L4, and L5, respectively) of long-term restoration soils when compared to that of the short-term restoration soil layers, while phosphorus limitation of microorganisms in subsoil (60-80 cm) was significantly increased by 17.38%. Soil nutrients, pH, moisture content, and microbial composition are the main drivers of microbial resource limitation in restoration, and their effects on microbial resource limitation were different in short- and long-term restoration. Meanwhile, key microbial taxa have a significant impact on microbial resource limitation, especially in short-term restoration soils. This study suggested that vegetation restoration significantly affected soil microbial resource limitation, and could alleviate microbial resource limitations by adding nutrients, thus accelerating the process of vegetation restoration in alpine ecosystems.

Climate Warming-Driven Changes in the Molecular Composition of Soil Dissolved Organic Matter Across Depth: A Case Study on the Tibetan Plateau.

Dissolved organic matter (DOM) is critical for soil carbon sequestration in terrestrial ecosystems. DOM molecular composition varies with soil depth. However, the spatial heterogeneity of depth-dependent DOM in response to climate warming remains unclear, especially in alpine ecosystems. In this study, the DOM of alpine meadow soil samples was characterized comprehensively by using spectroscopy and mass spectrometry, and open-top chambers (OTCs) were employed to simulate warming. It was found that climate warming had the greatest impact on the upper layer (0-30 cm), followed by the lower layer (60-80 cm), while the middle layer (30-60 cm) was the most stable among the three soil layers. The reasons for the obvious changes in DOM in the upper and lower layers of soil were further explained based on biotic and abiotic factors. Specifically, soil nutrients (NH4+-N, NO3--N, TC, and TP) affected the molecular composition of DOM in layer L1 (0-15 cm), while pH affected layer L5 (60-80 cm). Gemmatimonadetes, Proteobacteria, and Actinobacteria played important roles in the composition of DOM in the L5 layer (60-80 cm), while the dominant fungal groups affecting the DOM composition increased in the L1 layer (0-15 cm) under warming. In summary, this research has contributed to a deeper understanding of depth-dependent changes in DOM molecular composition in alpine ecosystems.

Potential feedback mediated by soil microbiome response to warming in a glacier forefield.

Mountain glaciers are retreating at an unprecedented rate due to global warming. Glacier retreat is widely believed to be driven by the physiochemical characteristics of glacier surfaces; however, the current knowledge of such biological drivers remains limited. An estimated 130 Tg of organic carbon (OC) is stored in mountain glaciers globally. As a result of global warming, the accelerated microbial decomposition of OC may further accelerate the melting process of mountain glaciers by heat production with the release of greenhouse gases, such as carbon dioxide (CO2 ) and methane. Here, using short-term aerobic incubation data from the forefield of Urumqi Glacier No. 1, we assessed the potential climate feedback mediated by soil microbiomes at temperatures of 5°C (control), 6.2°C (RCP 2.6), 11°C (RCP 8.5), and 15°C (extreme temperature). We observed enhanced CO2 -C release and heat production under warming conditions, which led to an increase in near-surface (2 m) atmospheric temperatures, ranging from 0.9°C to 3.4°C. Warming significantly changed the structures of the RNA-derived (active) and DNA-derived (total) soil microbiomes, and active microbes were more sensitive to increased temperatures than total microbes. Considering the positive effects of temperature and deglaciation age on the CO2 -C release rate, the alterations in the active microbial community structure had a negative impact on the increased CO2 -C release rate. Our results revealed that glacial melting could potentially be significantly accelerated by heat production from increased microbial decomposition of OC. This risk might be true for other high-altitude glaciers under emerging warming, thus improving the predictions of the effects of potential feedback on global warming.

Electron acceptors for anaerobic oxidation of methane drive microbial community structure and diversity in mud volcanoes.

Mud volcanoes (MVs) emit globally significant quantities of methane into the atmosphere, however, methane cycling in such environments is not yet fully understood, as the roles of microbes and their associated biogeochemical processes have been largely overlooked. Here, we used data from high-throughput sequencing of microbial 16S rRNA gene amplicons from six MVs in the Junggar Basin in northwest China to quantify patterns of diversity and characterize the community structure of archaea and bacteria. We found anaerobic methanotrophs and diverse sulfate- and iron-reducing microbes in all of the samples, and the diversity of both archaeal and bacterial communities was strongly linked to the concentrations of sulfate, iron and nitrate, which could act as electron acceptors in anaerobic oxidation of methane (AOM). The impacts of sulfate/iron/nitrate on AOM in the MVs were verified by microcosm experiments. Further, two representative MVs were selected to explore the microbial interactions based on phylogenetic molecular ecological networks. The sites showed distinct network structures, key species and microbial interactions, with more complex and numerous linkages between methane-cycling microbes and their partners being observed in the iron/sulfate-rich MV. These findings suggest that electron acceptors are important factors driving the structure of microbial communities in these methane-rich environments.

The Occurrence of Putative Nitric Oxide Dismutase (Nod) in an Alpine Wetland with a New Dominant Subcluster and the Potential Ability for a Methane Sink.

Recently, a new oxygenic pathway has been proposed based on the disproportionation of NO with putative NO dismutase (Nod). In addition to a new process in nitrogen cycling, this process provides ecological advantages for the degradation of substrates in anaerobic conditions, which is of great significance for wastewater treatment. However, the Nod distribution in aquatic environments is rarely investigated. In this study, we obtained the nod genes with an abundance of 2.38 ± 0.96 × 105 copies per gram of dry soil from the Zoige wetland and aligned the molecular characteristics in the corresponding Nod sequences. These Nod sequences were not only found existing in NC10 bacteria, but were also found forming some other clusters with Nod sequences from a WWTP reactor or contaminated aquifers. Moreover, a new subcluster in the aquifer-similar cluster was even dominant in the Zoige wetland and was named the Z-aquifer subcluster. Additionally, soils from the Zoige wetland showed a high potential rate (10.97 ± 1.42 nmol of CO2 per gram of dry soil per day) for nitrite-dependent anaerobic methane oxidation (N-DAMO) with low abundance of NC10 bacteria, which may suggest a potential activity of Nod in other clusters when considering the dominance of the Z-aquifer subcluster Nod. In conclusion, we verified the occurrence of Nod in an alpine wetland for the first time and found a new subcluster to be dominant in the Zoige wetland. Moreover, this new subcluster of Nod may even be active in the N-DAMO process in this alpine wetland, which needs further study to confirm.

Detection of bioavailable cadmium, lead, and arsenic in polluted soil by tailored multiple Escherichia coli whole-cell sensor set.

Microbial whole-cell sensor has been widely used to assess bioavailability and risk of toxic elements, but their environmental use is still limited due to the presence of other interfering pollutants and the nonspecific binding in cells, which leads to inaccurate results. Here, we proposed a strategy combining Escherichia coli sensor set with binary regression models for the specific detection of bioavailable cadmium (Cd), lead (Pb), and arsenic (As) in a co-polluted environment. Initial tests suggested that the sensor set respectively termed pcadCluc, pzntRluc, and parsRluc could be classified into two groups according to their specific response to Cd, Pb, and As: group 1 (pcadCluc and pzntRluc) induced by a Cd-Pb mix and group 2 (parsRluc) induced by a Cd-As mix. Based on the variance in responses of each sensor to mixtures of target elements, three binary linear equations for two sensor groups were set up to calculate the individual concentrations in the mixture solutions. This method was then used to quantify the bioavailable Cd, Pb, and As in soils from a co-polluted mining region and to compare the results with other methods. Results showed that the conventional single target sensor method overestimated the bioavailability of each element, while sensor set was credible for accurate bioavailable Cd, Pb, and As quantification and comparable with the results from inductively coupled plasma mass spectrometry (ICP-MS) analysis. Our method can potentially be extended to cover the specific detection of other bioavailable toxic elements in different environmental settings.

Chitosan multiple addition enhances laccase production from Trametes versicolor.

Chitosan multiple addition strategy was developed to improve laccase production from Trametes versicolor cultures. The optimized multiple addition strategy was carried out by two-time addition of 0.1 g L(-1) chitosan to a 2-day-old culture media, with 24-h interval between the treatments. Under these conditions, laccase activity of 644.9 U l(-1) was achieved on the seventh day and laccase production was improved by 93.5 % higher than the control. Chitosan treatment increased reactive oxygen species generation and extracellular protein concentration in the treated mycelia. In contrast, the inducer inhibited the mycelia growth. The result of the quantitative reverse transcription polymerase chain reaction showed that the copy number of the laccase gene transcript increased by 16.7-fold in the treated mycelia relative to the control. This study provides insight into some of the intrinsic metabolic processes involved in the upregulation of laccase production in the presence of chitosan inducer in fungal culture.

An N-acyl homoserine lactone synthase in the ammonia-oxidizing bacterium Nitrosospira multiformis.

The chemolithoautotrophic bacterium Nitrosospira multiformis is involved in affecting the process of nitrogen cycling. Here we report the existence and characterization of a functional quorum sensing signal synthase in N. multiformis. One gene (nmuI) playing a role in generating a protein with high levels of similarity to N-acyl homoserine lactone (AHL) synthase protein families was identified. Two AHLs (C14-AHL and 3-oxo-C14-AHL) were detected using an AHL biosensor and liquid chromatography-mass spectrometry (LC-MS) when nmuI, producing a LuxI homologue, was introduced into Escherichia coli. However, by extracting N. multiformis culture supernatants with acidified ethyl acetate, no AHL product was obtained that was capable of activating the biosensor or being detected by LC-MS. According to reverse transcription-PCR, the nmuI gene is transcribed in N. multiformis, and a LuxR homolog (NmuR) in this ammonia-oxidizing strain showed great sensitivity to long-chain AHL signals by solubility assay. A degradation experiment demonstrated that the absence of AHL signals might be attributed to the possible AHL-inactivating activities of this strain. To summarize, an AHL synthase gene (nmuI) acting as a long-chain AHL producer has been found in a chemolithotrophic ammonia-oxidizing microorganism, and the results provide an opportunity to complete the knowledge of the regulatory networks in N. multiformis.

The impacts of different long-term fertilization regimes on the bioavailability of arsenic in soil: integrating chemical approach with Escherichia coli arsRp::luc-based biosensor.

An Escherichia coli arsRp::luc-based biosensor was constructed to measure the bioavailability of arsenic (As) in soil. In previous induction experiments, it produced a linear response (R (2) = 0.96, P < 0.01) to As from 0.05 to 5 µmol/L after a 2-h incubation. Then, both chemical sequential extraction, Community Bureau of Reference recommended sequential extraction procedures (BCR-SEPs) and E. coli biosensor, were employed to assess the impact of different long-term fertilization regimes containing N, NP, NPK, M (manure), and NPK + M treatments on the bioavailability of arsenic (As) in soil. Per the BCR-SEPs analysis, the application of M and M + NPK led to a significant (P < 0.01) increase of exchangeable As (2-7 times and 2-5 times, respectively) and reducible As (1.5-2.5 times and 1.5-2.3 times, respectively) compared with the no fertilization treated soil (CK). In addition, direct contact assay of E. coli biosensor with soil particles also supported that bioavailable As in manure-fertilized (M and M + NPK) soil was significantly higher (P < 0.01) than that in CK soil (7 and 9 times, respectively). Organic carbon may be the major factor governing the increase of bioavailable As. More significantly, E. coli biosensor-determined As was only 18.46-85.17 % of exchangeable As and 20.68-90.1 % of reducible As based on BCR-SEPs. In conclusion, NKP fertilization was recommended as a more suitable regime in As-polluted soil especially with high As concentration, and this E. coli arsRp::luc-based biosensor was a more realistic approach in assessing the bioavailability of As in soil since it would not overrate the risk of As to the environment.

Immigrant Pantoea agglomerans embedded within indigenous microbial aggregates: a novel spatial distribution of epiphytic bacteria.

Immigrant bacteria located on leaf surfaces are important to the health of plants as well as to people who consume fresh fruits and vegetables. However, the spatial distribution and organization of these immigrant bacteria on leaf surfaces are still poorly understood. To examine the spatial organization of these strains, two bacterial strains on tobacco leaves: (1) an indigenous strain, Pseudomonas stutzeri Nov. Y2011 labeled with green fluorescent protein, and (2) an immigrant strain Pantoea agglomerans labeled with cyan fluorescent protein isolated from pear, were studied. Under moist conditions, P. agglomerans cells quickly disappeared from direct observation by laser-scanning confocal microscopy, although elution results indicated that large amounts of live cells were still present on the leaves. Following exposure to desiccation stress, particles of cyan fluorescent protein-labeled P. agglomerans were visible within cracked aggregates of P. stutzeri Nov. Y2011. Detailed observation of sectioned aggregates showed that colonies of immigrant P. agglomerans were embedded within aggregates of P. stutzeri Nov. Y2011. Furthermore, carbon-resource partitioning studies suggested that these two species could coexist without significant nutritional competition. This is the first observation of an immigrant bacterium embedding within aggregates of indigenous bacteria on leaves to evade harsh conditions in the phyllosphere.

Construction of a dual fluorescence whole-cell biosensor to detect N-acyl homoserine lactones.

Detection of N-acyl homoserine lactones (AHLs) is useful for understanding quorum sensing (QS) behaviors, including biofilm formation, virulence and metabolism. For detecting AHLs and indicating the host cells in situ, we constructed the plasmid pUCGMA2T(1-4) to make a dual fluorescent whole-cell biosensor based on the AhlIR AHL system of Pseudomonas syringae pv. syringae B728a. The plasmid contains three components: constitutively expressed P(npatII::gfp) for indicating host cells, P(ahlI::mcherry) that produces red fluorescence in response to AHL, and the ahlR gene that encodes an AHL regulatory protein. Meanwhile, two copies of T(1-4) (four tandem copies of a transcriptional terminator) were added into the plasmid to reduce background. The results showed that when the plasmid was placed into Escherichia coli, the dual fluorescence whole-cell biosensor was able to respond with red fluorescence within 6 hr to 5 x 10(-8)-1 x 10(-5) mol/L of 3OC6-HSL. Bright green fluorescence indicated the host cells. Furthermore, when the plasmid was transferred to wildtype Pseudomonas PhTA125 (an AHL-producing bacterium), it also showed both green and red fluorescence. This result demonstrates that this plasmid can be used to construct whole-cell indicators that can indicate the AHL response and spatial behaviors of microbes in a microenvironmental niche.

Investigating the degradation potential of microbial consortia for perfluorooctane sulfonate through a functional "top-down" screening approach.

Perfluorooctane sulfonate (PFOS) is a prominent perfluorinated compound commonly found in the environment, known to pose various risks to human health. However, the removal of PFOS presents significant challenges, primarily due to the limited discovery of bacteria capable of effectively degrading PFOS. Moreover, single degradation bacteria often encounter obstacles in individual cultivation and the breakdown of complex pollutants. In contrast, microbial consortia have shown promise in pollutant degradation. This study employed a continuous enrichment method, combined with multiple co-metabolic substrates, to investigate a microbial consortium with the potential for PFOS degradation. By employing this methodology, we effectively identified a microbial consortium that demonstrated the capacity to reduce PFOS when exposed to an optimal concentration of methanol. The consortium predominantly comprised of Hyphomicrobium species (46.7%) along with unclassified microorganisms (53.0%). Over a duration of 20 days, the PFOS concentration exhibited a notable decrease of 56.7% in comparison to the initial level, while considering the exclusion of adsorption effects. Furthermore, by comparing the predicted metabolic pathways of the microbial consortium with the genome of a known chloromethane-degrading bacterium, Hyphomicrobium sp. MC1, using the KEGG database, we observed distinct variations in the metabolic pathways, suggesting the potential role of the unclassified microorganisms. These findings underscore the potential effectiveness of a "top-down" functional microbial screening approach in the degradation of stubborn pollutants.

Selenium volatilization in plants, microalgae, and microorganisms.

The augmented prevalence of Se (Se) pollution can be attributed to various human activities, such as mining, coal combustion, oil extraction and refining, and agricultural irrigation. Although Se is vital for animals, humans, and microorganisms, excessive concentrations of this element can give rise to potential hazards. Consequently, numerous approaches have been devised to mitigate Se pollution, encompassing physicochemical techniques and bioremediation. The recognition of Se volatilization as a potential strategy for mitigating Se pollution in contaminated environments is underscored in this review. This study delves into the volatilization mechanisms in various organisms, including plants, microalgae, and microorganisms. By assessing the efficacy of Se removal and identifying the rate-limiting steps associated with volatilization, this paper provides insightful recommendations for Se mitigation. Constructed wetlands are a cost-effective and environmentally friendly alternative in the treatment of Se volatilization. The fate, behavior, bioavailability, and toxicity of Se within complex environmental systems are comprehensively reviewed. This knowledge forms the basis for developing management plans that aimed at mitigating Se contamination in wetlands and protecting the associated ecosystems.

Tibetan Plateau grasslands might increase sequestration of microbial necromass carbon under future warming.

Microbial necromass carbon (MNC) can reflect soil carbon (C) sequestration capacity. However, changes in the reserves of MNC in response to warming in alpine grasslands across the Tibetan Plateau are currently unclear. Based on large-scale sampling and published observations, we divided eco-clusters based on dominant phylotypes, calculated their relative abundance, and found that their averaged importance to MNC was higher than most other environmental variables. With a deep learning model based on stacked autoencoder, we proved that using eco-cluster relative abundance as the input variable of the model can accurately predict the overall distribution of MNC under current and warming conditions. It implied that warming could lead to an overall increase in the MNC in grassland topsoil across the Tibetan Plateau, with an average increase of 7.49 mg/g, a 68.3% increase. Collectively, this study concludes that alpine grassland has the tendency to increase soil C sequestration capacity on the Tibetan Plateau under future warming.

Magnetic field-assisted surface engineering technology for active regulation of Fe3O4 medium to enable the laccase electrochemical biosensing of catechol with visible stripe patterns.

BACKGROUND: Catechol (CC), a prevalent phenolic compound, is a byproduct in various agricultural, chemical, and industrial processes. CC detection is crucial for safeguarding water quality and plays a pivotal role in enhancing the overall quality of life of individuals. Electrochemical biosensors exhibit rapid responses, have small sizes, and can be used for real-time monitoring. Therefore, the development of a fast and sensitive electrochemical biosensor for CC detection is crucial. RESULT: In this study, a laccase-based electrochemical biosensor for detection of CC is successfully developed using Fe3O4 nanoparticles as medium and optimized by applying a magnetic field. This research proposes a unique strategy for biosensor enhancement by actively controlling the distribution of magnetic materials on the electrode surface through the application of a magnetic field, resulting in a visibly alternating stripe pattern. This approach effectively disperses magnetic particles, preventing their aggregation and reducing the boundary layer thickness, enhancing the electrochemical response of the biosensor. After fabrication condition optimization, CC is successfully detected using this biosensor. The fabricated sensor exhibits excellent performance with a wide linear detection range of 10-1000 µM, a low detection limit of 1.25 µM, and a sensitivity of 7.9 µA/mM. The fabricated sensor exhibits good selectivity and reliable detection in real water samples. In addition, the laccase-based sensor has the potential for the fast and accurate monitoring of CC in olive oil. SIGNIFICANCE: The magnetic field optimization in this study significantly improved the performance of the electrochemical biosensor for detecting CC in environmental samples. Overall, the sensor developed in this study has the potential for fast and accurate monitoring of CC in environmental samples, highlighting the potential importance of a magnetic field environment in improving the performance of catechol electrochemical biosensors.

Quorum quenching in culturable phyllosphere bacteria from tobacco.

Many Gram-negative plant pathogenic bacteria employ a N-acylhomoserine lactone (AHL)-based quorum sensing (QS) system to regulate their virulence traits. A sustainable biocontrol strategy has been developed using quorum quenching (QQ) bacteria to interfere with QS and protect plants from pathogens. Here, the prevalence and the diversity of QQ strains inhabiting tobacco leaf surfaces were explored. A total of 1177 leaf-associated isolates were screened for their ability to disrupt AHL-mediated QS, using the biosensor Chromobacterium violaceum CV026. One hundred and sixty-eight strains (14%) are capable of interfering with AHL activity. Among these, 106 strains (63%) of the culturable quenchers can enzymatically degrade AHL molecules, while the remaining strains might use other QS inhibitors to interrupt the chemical communication. Moreover, almost 79% of the QQ strains capable of inactivating AHLs enzymatically have lactonase activity. Further phylogenetic analysis based on 16S rDNA revealed that the leaf-associated QQ bacteria can be classified as Bacillus sp., Acinetobacter sp., Lysinibacillus sp., Serratia sp., Pseudomonas sp., and Myroides sp. The naturally occurring diversity of bacterial quenchers might provide opportunities to use them as effective biocontrol reagents for suppressing plant pathogen in situ.

Bioactive molecules in soil ecosystems: masters of the underground.

Complex biological and ecological processes occur in the rhizosphere through ecosystem-level interactions between roots, microorganisms and soil fauna. Over the past decade, studies of the rhizosphere have revealed that when roots, microorganisms and soil fauna physically contact one another, bioactive molecular exchanges often mediate these interactions as intercellular signal, which prepare the partners for successful interactions. Despite the importance of bioactive molecules in sustainable agriculture, little is known of their numerous functions, and improving plant health and productivity by altering ecological processes remains difficult. In this review, we describe the major bioactive molecules present in below-ground ecosystems (i.e., flavonoids, exopolysaccharides, antibiotics and quorum-sensing signals), and we discuss how these molecules affect microbial communities, nutrient availability and plant defense responses.

Profile of the culturable microbiome capable of producing acyl-homoserine lactone in the tobacco phyllosphere.

Bacterial populations coexisting in the phyllosphere niche have important effects on plant health. Quorum sensing (QS) allows bacteria to communicate via diffusible signal molecules, but QS-dependent behaviors in phyllosphere bacterial populations are poorly understood. We investigate the dense and diverse N-acyl-homoserine lactone (AHL)-producing phyllosphere bacteria living on tobacco leaf surfaces via a culture-dependent method and 16S rRNA gene sequencing. Our results indicated that approximately 7.9%-11.7% of the culturable leaf-associated bacteria have the ability to produce AHL based on the assays using whole-cell biosensors. Sequencing of the 16S rRNA gene assigned the AHL-producing strains to two phylogenetic groups, with Gammaproteobacteria (93%) as the predominant group, followed by Alphaproteobacteria. All of the AHL-producing Alphaproteobacteria were affiliated with the genus Rhizobium, whereas the AHL-producing bacteria belonging to the Gammaproteobacteria mainly fell within the genera Pseudomonas, Acinetobacter, Citrobacter, Enterobacter, Pantoea and Serratia. The bioassays of supernatant extracts revealed that a portion of the strains have a remarkable AHL profilefor AHL induction activity using the two different biosensors, and one compound i nthe active extract of a representative isolate, NTL223, corresponded to 3-oxo-hexanoyl-homoserine lactone. A large population size and diversity of bacteria capable of AHL-driven QS were found to cohabit on leaves, implying that cross-communication based AHL-type QS may be common in the phyllosphere. Furthermore, this study provides a general snapshot of a potential valuable application of AHL-producing bacteria inhabiting leaves for their presumable ecological roles in the phyllosphere.

Soil bacterial communities associated with multi-nutrient cycling under long-term warming in the alpine meadow.

Introduction: The functions of terrestrial ecosystems are mainly maintained by bacteria, as a key component of microorganisms, which actively participate in the nutrient cycling of ecosystems. Currently, there are few studies have been carried out on the bacteria contributing to the soil multi-nutrient cycling in responding to climate warming, which hampers our obtainment of a comprehensive understanding of the ecological function of ecosystems as a whole. Methods: In this study, the main bacteria taxa contributing to the soil multi-nutrient cycling under the long-term warming in an alpine meadow was determined based onphysichemical properties measurement and high-throughput sequencing, and the potential reasons that warming altered the main bacteria contributing to the soil multi-nutrient cycling were further analyzed. Results: The results confirmed that the bacterial ß-diversity was crucial to the soil multi-nutrient cycling. Furthermore, Gemmatimonadetes, Actinobacteria, and Proteobacteria were the main contributors to the soil multi-nutrient cycling, and played pivotal roles as keystone nodes and biomarkers throughout the entire soil profile. This suggested that warming altered and shifted the main bacteria contributing to the soil multi-nutrient cycling toward keystone taxa. Discussion: Meanwhile, their relative abundance was higher, which could make them have the advantage of seizing resources in the face of environmental pressures. In summary, the results demonstrated the crucial role of keystone bacteria in the multi-nutrient cycling under the climate warming in the alpine meadow. This has important implications for understanding and exploring the multi-nutrient cycling of alpine ecosystems under the global climate warming.

Niche-mediated bacterial community composition in continental glacier alluvial valleys under cold and arid environments.

Introduction: Bacteria are an essential component of glacier-fed ecosystems and play a dominant role in driving elemental cycling in the hydrosphere and pedosphere. However, studies of bacterial community composition mechanisms and their potential ecological functions from the alluvial valley of mountain glaciers are extremely scarce under cold and arid environments. Methods: Here, we analyzed the effects of major physicochemical parameters related to soil on the bacterial community compositions in an alluvial valley of the Laohugou Glacier No. 12 from the perspective of core, other, and unique taxa and explored their functional composition characteristics. Results and discussion: The different characteristics of core, other, and unique taxa highlighted the conservation and difference in bacterial community composition. The bacterial community structure of the glacial alluvial valley was mainly affected by the above sea level, soil organic carbon, and water holding capacity. In addition, the most common and active carbon metabolic pathways and their spatial distribution patterns along the glacial alluvial valley were revealed by FAPTOTAX. Collectively, this study provides new insights into the comprehensive assessment of glacier-fed ecosystems in glacial meltwater ceasing or glacier disappearance.