[Objective] Soil salinization is a serious threat to land health, and microbial remediation of saline-alkali soil is an eco-friendly and practical approach. Endophytic fungi can enhance host resistance to both biotic and abiotic stresses. Consequently, there is a need for further research on the biological characteristics of endophytic fungi. Such research can expand the existing endophytic fungal database and provide elite strains and effective strategies for the green remediation of saline-alkali soil and soil restoration. [Methods] The characteristics of the fungal strain were analyzed by plate culture under stress, scanning electron microscopy (SEM), and multi-gene phylogenetic analysis. The colonization of the strain in rice roots was examined by GFP fluorescence labeling, trypan blue staining, SEM, and colonization curve plotting. Pot experiments under stress and non-stress conditions, the peroxidase activity assay, transcriptome analysis, and gene expression analysis were carried out to decipher the mechanism by which the strain enhanced the salt tolerance of rice plants. [Results] An endophytic fungal strain, LW2, capable of enhancing the salt tolerance of host rice plants, was obtained. The phylogenetic tree showed that LW2 clustered with Ophioceras leptosporum CBS 894.70 in the same minimal clade, and thus the strain was identified as O. leptosporum LW2. LW2 successfully colonized rice roots and promoted the growth of potted rice. The rice plants co-cultured with LW2 showed significant increases in the fresh weight, plant height, and stem width. The pot experiments under salt stress showed that LW2 improved the salt tolerance of rice by increasing the plant height and stem width under stress conditions while alleviating stress-induced wilting and yellowing. LW2 mitigated salt-induced damage of rice by increasing the peroxidase activity and promoting reactive oxygen species (ROS) scavenging. In addition, LW2 regulated the expression of EIL1 and HKTs in the ethylene signaling pathway which affected ion transport, thereby enhancing rice salt tolerance. [Conclusion] This study identified an endophytic fungal strain, O. leptosporum LW2, capable of enhancing the salt tolerance of host rice. We preliminarily investigate the salt tolerance mechanism of this strain, providing scientific evidence and an elite strain for microbial remediation of saline-alkaline soil and the development of green agriculture.

[Objective] To screen CO₂-fixing microbial strains in grassland soil, clarify their physiological and biochemical characteristics, and determine their optimal CO₂ fixation conditions, providing a theoretical basis for understanding the mechanisms of soil CO₂ fixation and enhancing grassland soil carbon sink. [Methods] The carbon-free solid medium and the dilution plating method were employed to isolate CO₂-fixing microbial strains from grassland soil in the Loess Plateau. The strains were identified via 16S rRNA gene sequencing. Physiological and biochemical characteristics of the strains were determined by Gram staining and starch hydrolysis, indole production, methyl red, and lactic acid fermentation tests. Culture experiments with carbon-free liquid medium and sterilized soil were carried out to assess the CO₂ fixation efficiency under varying temperatures (20-40 ℃), soil moisture levels (3.00%-27.00%), and the presence of electron donors (NaNO₂ and Na₂S). [Results] Nine bacterial strains with effective CO₂ fixation were isolated, belonging to Bacillus, Streptomyces, Sinorhizobium, Agrobacterium, Enterobacter, Brevundimonas, and Prolinoborus. Among them, strains A4 (Agrobacterium) and A7 (Brevundimonas) exhibited the highest CO₂ fixation efficiency (P<0.05), both being Gram-positive. Optimal conditions for CO₂ fixation of the nine strains were 25-30 ℃ and soil moisture of 3.00%, 15.00%, or 27.00% (P<0.05). Electron donor supplementation enhanced CO₂ fixation efficiency, and the enhancement effect followed the order: single addition of NaNO₂>single addition of Na₂S>co-addition of NaNO₂+Na₂S (P<0.05). [Conclusion] This study identified the dominant CO₂-fixing microbial strains and the conditions suitable for CO₂ fixation, providing a theoretical basis and technical support for enhancing the carbon sink of the terrestrial ecosystem on the Loess Plateau and mitigating the greenhouse effect.

[Objective] To further investigate the role of arsL and arsM genes in the synthesis of arsinothricin (AST) and the effects of AST on the community structure of soil bacteria. [Methods] Using Burkholderia oklahomensis NCTC 13388 as the research object, we obtained its BoarsL and BoarsM genes via PCR amplification, constructed recombinant plasmids pET21b-BoarsL and pET28a-BoarsM, and transformed them into the competent cells of Escherichia coli expression strain Rosetta(DE3). In addition, we employed high-throughput sequencing technology to analyze the effects of different concentrations of AST treatment on the composition and diversity of soil bacterial communities. [Results] Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) detected target proteins with relative molecular weights of 47.79 kDa and 41.50 kDa in recombinant strains, indicating successful expression of BoArsL and BoArsM. Cells expressing only the BoarsL gene produced AST-OH and a small amount of AST, while cells expressing only the BoarsM gene produced only a small amount of dimethylarsinic acid. Additionally, statistical analysis indicated that AST treatment at different concentrations had a significant impact on the alpha diversity of soil bacterial communities (P<0.05), as evidenced by significant differences in both the Chao1 and Shannon indices. The low-concentration treatment group had higher soil bacteria diversity and richness than the control group, whereas the high-concentration treatment caused statistically significant declines in both diversity and species richness. Further analysis revealed that bacterial community composition at the genus level also exhibited significant differences among the AST treatment groups of different concentrations (P<0.05), and high concentrations of AST significantly enriched bacteria of the genus Burkholderia-Caballeronia-Paraburkholderia but significantly inhibited bacteria of the genera Clostridium_sensu_stricto and Sedimentibacter. [Conclusion] The BoarsL gene of B. oklahomensis NCTC 13388 is essential for the biosynthesis of AST. High concentrations of AST significantly affect the structure of soil bacterial communities.

[Objective] To study the mechanisms of mutual promotion between chemolithoauto-trophic sulfur-oxidizing bacteria and chemoheterotrophic bacteria under co-culture based on carbon metabolism. [Methods] Ion chromatography was employed to determine the concentrations of S₂O₃^2‒ (thiosulfate) and SO₄^2‒ (sulfate). Bacterial growth dynamics were monitored by the dilution plate method. Extracellular carbon characteristics were analyzed via total organic carbon analyzer measurement and LC-MS. Cellular morphology was observed by scanning electron microscopy. The relative mRNA levels of related genes were quantified by RT-qPCR. [Results] During the growth process, sulfur-oxidizing bacteria continuously fixed inorganic carbon and secreted organics, providing a stable carbon source for the growth of heterotrophic bacterium. In return, heterotrophic bacteria significantly enhanced the sulfur-oxidizing and carbon-fixing capabilities of sulfur-oxidizing bacteria. This was evidenced by the significantly up-regulated expression of the enzyme gene soxB involved in sulfur oxidation and the RubisCO gene cbbL involved in carbon fixation. Additionally, the production of extracellular polymeric substances was induced, which enhanced the biofilm formation. [Conclusion] This study elucidated the interaction mechanisms between sulfur-oxidizing bacteria and heterotrophic bacteria, particularly the significant enhancement of the carbon-fixing capability of sulfur-oxidizing bacteria. The findings provide a new perspective for the enrichment culture of chemolithoautotrophic bacteria and for understanding the carbon fixation mechanisms of autotrophic sulfur-oxidizing bacteria in microbial communities. Additionally, this study offers theoretical support for the low-carbon and efficient treatment of wastewater.

[Objective] To investigate the bio-weathering effects and mechanisms of Acidithiobacillus ferrooxidans on granite under acidic conditions (pH 2.0). [Methods] A 36-day immersion experiment was conducted, comparing the microbial group, acid solution group (pH 2.0, H₂SO₄), and pure culture medium (control) group. Physicochemical parameters [pH, redox potential (Eh), and electrical conductivity (EC)] of the soultion, surface chromaticity (CIE-Lab) of granite, and mineral dissolution characteristics were analyzed. [Results] The microbial group significantly accelerated granite weathering, forming a distinct weathered layer on the surface after 9 days. During the initial phase (0‒3 days), plagioclase dissolution caused a pH increase followed by stabilization. Fe³⁺ accumulation-dominated Eh and EC were regulated by both the initial ion background and weathering products. After bio-weathering, the granite exhibited a decrease of 11.6 in L* (reduced brightness), an increase of 6.8 in a* value (enhanced reddish-brown tone), and an increase of 9.6 in b* value (increased bluish tone). Surface reddish-brown areas were directly correlated with jarosite deposition. [Conclusion] Under acidic conditions, A. ferrooxidans accelerate granite weathering via Fe³⁺-mediated redox reactions. The chromaticity parameters (ΔL*, Δa*, and Δb*) and morphological characteristics serve as indicators for rapidly assessing weathering intensity. These findings provide a novel basis for evaluating weathering risks caused by acid mine wastewater in surrounding rocks and guiding ecological remediation.

Organic matter degradation in shallow lake sediments is a key process in regulating the carbon cycle and greenhouse gas emissions, while the mechanism by which submerged plant residue degradation regulates the long-term succession of microbial communities has not yet been clarified. [Objective] To investigate the mechanisms of microbial community succession driven by submerged plant residue degradation on long time scales. [Methods] We investigated the degradation dynamics of Potamogeton wrightii residues in Taihu Lake sediments through a 4-year microcosmic simulation experiment and analyzed in detail the dynamic impacts of organic matter fraction evolution and extracellular enzyme activities on microbial community succession. [Results] The rapid consumption of labile organic matter pool was accompanied by a surge in β- glucosidase activity, while the accumulation of recalcitrant organic matter pool was coupled with a lagged response of phenol oxidase activity. Microbial communities showed significant functional differentiation, with Bacillota and Basidiomycota dominating the degradation of recalcitrant organic matter pool in bacterial and fungal communities, respectively, revealing the metabolic division of labor in the degradation of lignin-like polymers. Variance decomposition showed that both labile and recalcitrant organic matter pools independently explained microbial community variations, highlighting the role of chemical complexity of organic matter in screening functional taxa. [Conclusion] Degradation of submerged plant residues significantly drove microbial community structure succession in the microcosmic culture system, and microbial community composition and organic matter fractions showed synergistic changes. In addition, the degradation promoted the growth of microorganisms with different growth strategies. This study elucidates the dynamic interactions between microbial functional differences and organic matter pool complexity in the degradation of submerged plant residues, providing a theoretical basis for carbon stability assessment and ecological restoration of shallow lakes.

Microplastics are novel pollutants that are widespread in the oceans, soil, and atmosphere, affecting the process of pollutant transport and transformation through physical, chemical or biological interactions. The heavy metal pollution caused by mining activities in the soil and water environment around antimony mining regions is increasing year by year. However, the effect of microplastics on the biogeochemical transformation of heavy metal contaminants in the mining regions has been rarely reported. [Objective] To understand the effects of microplastic type, size and concentration on microbially mediated antimony release from stibnite. [Methods] We took Pseudomonas sp. J-1 with strong antimony tolerance and promoting antimony release and widely used polypropylene, polyvinyl chloride, and polystyrene as the objects of the study. The changes in pH, redox potential (ORP), microbial biomass, and antimony concentration were analyzed. Furthermore, microplastic adsorption of antimony under different pH values was studied, and confocal laser scanning microscopy (CLSM) and scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS) were employed to reveal the mechanism by which microplastics affected the biogeochemical cycle of antimony. [Results] Polypropylene with a particle size of 13 μm and a high concentration had the strongest inhibitory effect on stibnite dissolution with the participation of Pseudomonas sp. J-1. Microplastics inhibited the growth of the bacterial colony, which led to weakened promoting effect on the release of antimony, and the growth of Pseudomonas sp. J-1 was even completely inhibited by the high concentration of microplastics. Microplastics were able to adsorb antimony, while the adsorption capacity was independent of solution pH. [Conclusion] The type, particle size, and concentration of microplastics are the key factors affecting the stibnite dissolution mediated by Pseudomonas sp. J-1 and they indirectly affect stibnite dissolution mainly by influencing microbial growth.

[Objective] To obtain the enriched groups of target microorganisms from the natural environment of the study area and establish the pure culture, improve the key link of the basic research on bio-geochemistry in methane leakage areas, and provide ideas and references for the enrichment and culture of other unknown microorganisms. [Methods] Microorganisms in marine sediments from methane leakage areas were isolated and cultured, and a sound experimental methodology for marine microorganisms was refined, including on-site treatment of microbial samples, preparation and sterilization of anaerobic culture media, and enrichment, culture, and isolation of microorganisms. High-throughput sequencing of microorganisms was conducted for gene sequencing and microbial identification, and different experimental conditions and experimental cycles were designed for in vivo microbial culture experiments. The short-term experiment (1.5 d) was conducted with the single factor method to study the effects of environmental factors (light, medium concentration, temperature, and pH) on microorganisms. The medium-term experiment (22 d) verified the results of the short-term experiment and determined the more suitable culture conditions. The long-term experiment (more than 250 d) was carried out to further study the growth status and activity of enriched microbial groups under specific conditions by real-time quantitative tracking of microorganisms. [Results] In the short-term culture, the activity of anaerobic sludge microbial suspension significantly increased under natural light (reached the peak at the time point of 17 h, with the iron concentration of 16.7 mg/L, four times the initial value), while the buffer period was prolonged in the dark environment (0-15 h). The activity of marine sediment microbial suspension was better in the dark environment (with high values at time points of 14 h/35 h), and the activity in the acid/base environment (pH 5.0/9.0) was higher than that in the neutral environment (iron concentrations of 4.3 mg/L vs. 11.1 mg/L, respectively). In the medium-term culture, the activity of anaerobic sludge microbial suspension was stable under 4 ℃ and acid conditions (with the decrease of only 20% in iron concentration), while the marine sediment microbial suspension preferred higher temperature and alkaline environment (with the activity increased after adaptation to pH 9.0). The global analysis showed that the first 15 days were the temperature adaptation period, and then temperature became the key regulatory factor. In the long-term culture, the activity of anaerobic sludge microbial suspension fluctuated periodically (first decreasing and then increasing after change of the culture medium every 50 days), while it declined irreversibly after 150 d. The marine sediment microbial suspension showed strong adaptability (with the activity peaked on days 117-145 under high pressure and the estimated doubling cycle of about 130 d) and maintained serrated stable activity under room pressure (iron concentration of 3.0-10.4 mg/L). [Conclusion] Anaerobic sludge microorganisms are sensitive to light and medium concentration. Their activity is improved by short-term light but inhibited by long-term light. Dark environment and 100% concentration medium are more suitable for growth of anaerobic sludge microorganisms (4 ℃, acidic environment, doubling cycle of 15 d). However, marine sediment microorganisms under the dark+100% medium and high temperature+alkaline environment conditions demonstrate stronger adaptability. Although their short-term activity is less affected by light, it takes about 130 days to double, and the adaptability to the high pressure environment significantly affects the growth process.

Ion-adsorbed rare earth ore is a strategically important resource of global concern, playing a vital role in developing multiple industries in China. However, large-scale mining activities have led to soil degradation, nutrient losses, and heavy metal pollution. [Objective] To analyze the microbial community structure in the vertical profile of an ion-adsorbed rare earth mine and its response to environmental factors, exploring the depth-dependent variation pattern of microbial communities and their relationship with environmental variables. The findings will provide a scientific basis for the ecological restoration of polluted mining areas. [Methods] The soil samples were collected from an ion-adsorbed rare earth mine within the depth range of 1–15 m, and the physicochemical properties of the soil were analyzed. High-throughput sequencing was employed to investigate the distribution patterns of soil microorganisms along the vertical profile of the mine and to establish the relationships between environmental factors and microbial community succession. [Results] As the mining depth increased, soil pH and total carbon (TC) gradually decreased. Ammonia nitrogen (NH₃-N) was the dominant N form in the mine soil, reaching up to 13.0 mg/kg in the intermediate soil layers. Iron (Fe), magnesium (Mg), and total rare earth elements (TREEs) were abundant, with higher accumulation levels in deeper soil layers. The microbial communities exhibited a distinct succession pattern along the vertical profile of the mine. Alpha diversity indexes (e.g., Chao1 for richness and Shannon for diversity) indicated a decline in soil microbial diversity with the increase in depth. In contrast, beta diversity analyses such as principal component analysis (PCA) and principal co-ordinates analysis (PCoA) revealed significant clustering differences among soil layers. Correlation analysis demonstrated that environmental factors regulated microbial community differentiation, and the soil nutrient cycling characteristics were distinct across different depth layers. The dominant bacterial phyla in the mine soil included Chloroflexota, Pseudomonadota, Actinomycetota, and Acidobacteriota, which likely played crucial roles in biogeochemical cycles. The microbial succession in the mine soil followed a depth-dependent pattern. Specifically, Chloroflexota, Acidobacteriota, and Actinomycetota predominated in the surface soil. In intermediate layers, the relative abundance of Chloroflexota declined, while Pseudomonadota became dominant with a relative abundance of 60%. In deep layers with extreme anaerobic environments, Pseudomonadota adapted metabolically to oligotrophic conditions, emerging as the dominant group with a relative abundance of 70%. These microorganisms play vital roles in the cycling of soil carbon (C) and nitrogen (N). For C cycling, surface microorganisms primarily relied on the Calvin cycle for C fixation. Microorganisms adopt a glycolysis strategy and the TCA cycle to meet metabolic demands in intermediate layers, where a microaerobic-anaerobic transition occurs. Deep-layer anaerobic conditions drove microorganisms to employ fermentation as the main metabolic pathway. As for N cycling, surface microorganisms mainly adopted dissimilatory nitrate reduction to ammonium (DNRA); microorganisms in intermediate layers were pivotal in denitrification; deep-layer anaerobic microorganisms employed a dual metabolic system of DNRA (primary) and denitrification (secondary), exhibiting significantly higher N transformation intensity than surface microorganisms. [Conclusion] The microbial communities in the vertical profile of the ion-adsorbed rare earth mine exhibit a distinct differentiation pattern and are closely correlated with multiple environmental factors, suggesting their potential role in the nutrient cycling of the mine soil. The findings provide a scientific basis for future regulation and remediation of pollution in rare earth mining areas.

[Objective] This study systematically reviews the research trends in microbially induced calcium carbonate precipitation (MICP) over the past 25 years. Through bibliometric analysis, we aim to elucidate the developmental trajectory, research hotspots, and academic impact distribution of MICP, offering data-driven insights for researchers and proposing strategic priorities for future studies. [Methods] A comprehensive dataset of 1 947 publications was extracted from the Web of Science Core Collection (1999-2024). Bibliometric analysis and CiteSpace visualization tools were employed to quantify publication volume, authorship patterns, country/institutional contributions, and keywords dynamics. Time-series analysis and network mapping were integrated to decode the evolutionary pathways and interdisciplinary frontiers of the field. [Results] Annual MICP publications exhibit sustained growth, with China emerging as the dominant contributor, accounting for 47.71% of global output. Leading institutions such as Nanyang Technological University, Chinese Academy of Sciences, Southeast University, and Chongqing University demonstrate strong academic influence through high publication output and citation frequency. The research hotspots are primarily concentrated in soil improvement, self-healing concrete, and bioremediation. Keywords clustering analysis reveals emerging interdisciplinary frontiers at the intersection of environmental geotechnics and biomaterials applications. [Conclusion] MICP research has entered a phase of rapid multidisciplinary integration, with China leading global advancements. Future efforts should prioritize fundamental studies on bio-mineral interaction mechanisms, accelerate MICP applications in environmental remediation and smart materials, and develop green, sustainable processes to enhance its role in carbon neutrality and ecological engineering.