Objective Although the coupling of carbon (C), nitrogen (N), and sulfur (S) cycles is crucial in mangrove ecosystems, direct experimental evidence from pure microbial cultures demonstrating this coupling remains scarce. This work aims to elucidate the coupling process of C, N, and S cycles in mangrove-derived Vibrio ziniensis ZWAL4003. Methods An integrated approach combining genomic analysis, phylogenetic analysis, 16S rRNA gene abundance quantification, and physiological-biochemical characterization was employed to explore the potential coupling process of element metabolism in ZWAL4003. Results The genome of ZWAL4003 carried genes associated with complete metabolic pathways including tricarboxylic acid cycle, oxidative phosphorylation, dissimilatory nitrate reduction to ammonium, and assimilatory sulfur reduction. Glucose, sucrose, starch, and glycerol as C sources significantly enhanced the nitrate reduction activity of ZWAL4003. NaNO₃ as the N source inhibited the sulfate reduction activity of ZWAL4003. Na₂S₂O₃, Na₂SO₄, and Na₂SO₃ as the S sources inhibited the nitrate reduction activity. Furthermore, V. ziniensis strains were widely distributed in the mangrove sediments along the southeast coast of China, with the relative abundance of 0.004 19%-0.073 04%, showing an increasing trend from north to south. Conclusion This study demonstrates that C source utilization promotes nitrate and sulfate reductions, while mutual inhibition exists between nitrate and sulfate reductions, forming the coupling process of C, N, and S metabolisms in ZWAL4003. The wide distribution of V. ziniensis strains in the mangrove ecosystems of China suggests the potential important role of V. ziniensis as an executor in coupling element cycles. These findings enrich our understanding of the integrity of microbe-driven geochemical processes in mangrove ecosystems.

Objective Revealing the succession patterns of soil microbial communities and their carbon cycle functions in the 0-20 cm topsoil following the conversion of natural forests to other land use types is critical for elucidating microbial carbon sequestration mechanisms and maintaining soil health. Methods The investigation selected natural forests in the southern Dongting Lake region and their converted plantations, paddy fields, and grasslands as research subjects. Metagenomic techniques were employed to systematically analyze changes in microbial community composition and carbon cycling genes in the 0-20 cm topsoil, as well as to identify key driving factors. Results Conversion of natural forests to plantations, paddy fields, and grasslands reduced soil bacterial diversity by 12%-24%. Fungal diversity in plantations and paddy fields was 65% and 76% lower than that in natural forests, respectively. Conversion of natural forests altered soil bacterial and fungal community composition. Soil available phosphorus content and pH value were identified as primary factors influencing bacterial diversity, whereas fungal diversity and community composition were mainly affected by soil available iron content. Following land use conversion, the relative abundance of carbon fixation genes ACAT/atoB and tktA/tktB decreased by 10%-45%. However, the relative abundance of ACO/acnA, korA/oorA/oforA, and mcmA1 was 25%-32% higher in grassland soil, and that of ppdK and korA/oorA/oforA was 13%-40% higher in paddy soil than in natural forest soil. Compared with natural forests, paddy fields and grasslands showed decreases of 39%-43% in the relative abundance of carbon decomposition genes bglX and amyA, while converted land use types showed increases of 77%-293% in the relative abundance of abfA and nplT. Conclusion Soil pH value and nitrate nitrogen content are identified as key environmental factors regulating the relative abundance of carbon fixation and decomposition genes. Therefore, scientific management of soil acidity or alkalinity and nitrogen levels can be considered as an effective strategy to enhance the carbon sequestration potential of soil microorganisms.

Yuncheng Salt Lake located in the southwest of Shanxi Province is one of the three major sodium sulfate inland salt lakes in the world, harboring rich microbial resources, while there is still a lack of systematic research on the archaeal diversity in this salt lake. Objective To explore the diversity of archaea in soil sediments of Yuncheng Salt Lake and analyze the influences of environmental factors on the diversity. Methods Soil physical and chemical analysis was carried out on 54 samples from 18 sampling sites in Yuncheng Salt Lake, and the effects of environmental factors on the archaeal diversity were analyzed by amplicon high-throughput sequencing. Results Amplicon analysis showed that Halobacteriota, Thermoproteota, Nanobdellota, Thermoplasmatota, and Asgardarchaeota were the main taxa. Among them, Halobacteriota and Thermoproteota were the dominant groups of archaea in the soil sediments of Yuncheng Salt Lake. The analysis of diversity and community composition showed that there were obvious differences in archaeal communities among different sampling sites. Redundancy analysis showed that total nitrogen, total carbon, ammonium nitrogen, and SO₄^2- had the greatest effect on the archaeal diversity in soil sediments, followed by nitrate nitrogen, Cl^-, Mg²⁺, and Na⁺, while Ca²⁺, total phosphorus, and total potassium had mild effects. Conclusion The archaeal community in soil sediments of Yuncheng Salt Lake has high diversity and is closely related to environmental factors. This study enriches the biological information of archaeal resources in soil sediments of Yuncheng Salt Lake and provides a theoretical basis for the mining and research of archaeal resources in salt lakes.

Objective The survival mechanisms of aerobic methylotrophs in oxygen-deficient environments represent a focal topic in current microbial ecology. This study aims to investigate the extracellular electron transfer (EET) mechanism by which the aerobic methylotroph Methylophilus sp. 14 utilizes insoluble iron minerals (ferrihydrite) under oxygen-deficient conditions and to elucidate the synergistic role of exogenous and endogenous electron shuttles in this process. Methods Anaerobic culture (initial O₂ level: 2%) of Methylophilus sp. 14 isolated from sediments of Fuxian Lake was conducted with methanol as the carbon source and ferrihydrite as the sole terminal electron acceptor. Iron reduction kinetics were measured along with electrochemical analyses (differential pulse voltammetry and cyclic voltammetry) and microscopic characterization (scanning/transmission electron microscopy) to systematically evaluate the iron-reducing capacity of the strain and explore the roles of exogenous shuttles (humic substances, HS; anthraquinone-2,6-disulfonate, AQDS) and endogenous flavins in electron transfer. Results Methylophilus sp. 14 coupled methanol oxidation with ferrihydrite reduction, increasing the Fe(II) concentration from 0.49 μmol/L to 8.29 μmol/L within 20 days and promoting the partial transformation of ferrihydrite into magnetite. Exogenous addition of HS and AQDS further enhanced Fe(II) production to 10.73 μmol/L and 11.22 μmol/L, respectively, improving the cumulative electron transfer efficiency by approximately 1.5 folds. Electrochemical analyses indicated that the redox potential of the bacterial cells was lower than that of ferrihydrite, thermodynamically favoring spontaneous electron transfer. Soluble AQDS formed a conductive microenvironment that accelerated electron flux. Notably, this study first revealed that Methylophilus sp. 14 synthesized and secreted flavins, whose extracellular concentration showed a strong positive correlation with the EET rate (r=0.94, P<0.001). Furthermore, exogenous shuttles stimulated increases of 30%‒50% in total flavin secretion. Flavins functioned as a critical electron bridge, mediating electron transfer from intracellular metabolism to exogenous shuttles and thereby establishing a cooperative electron transport chain. Conclusion This work reveals a novel EET strategy employed by aerobic methylotrophs to adapt to oxygen-deficient conditions. That is, exogenous electron shuttles not only construct an extracellular conductive microenvironment but also stimulate the secretion of endogenous flavins, resulting in a synergistic electron transfer mechanism that efficiently drives the reduction of solid-phase iron minerals. These findings deepen our understanding of the metabolic flexibility of aerobic microorganisms and their ecological role at aerobic-anerobic interfaces.

Objective To investigate the sedimentary characteristics of dolomite, the bacterial community structure, and their relationships with environmental factors in the sediments of Jibuhulangtu Salt Lake, Inner Mongolia. Methods Sediments were collected from four sites along an offshore-to-nearshore transect in Jibuhulangtu Salt Lake. Bacterial community composition, mineralogical characteristics, and physicochemical parameters of sediments were analyzed by 16S rRNA gene sequencing, X-ray diffraction with Rietveld refinement, and scanning electron microscopy with energy-dispersive spectroscopy, and ion chromatography. Results After removal of soluble salts, the dolomite content in the sediments ranged from 48.75% to 75.28%. The dolomite particles primarily exhibited a nano-spherical shape and transformed from regular spheres to spherical aggregates with the increase in depth. The Mg/Ca molar ratios of the dolomite ranged from 0.87 to 1.46, approaching the stoichiometric value (1.00) of ideal dolomite. At the phylum level, the five most abundant bacterial groups were Actinomycetota, Pseudomonadota, Gemmatimonadota, Chloroflexota, and Acidobacteriota. The sulfate-reducing phylum Desulfobacterota was also abundant (4.23%). Alpha diversity analysis revealed significant differences in bacterial community diversity among sampling sites (P<0.05), with site J4 exhibiting the highest species richness but the lowest evenness. Redundancy analysis indicated that the concentrations of SO₄^2-, Mg²⁺, K⁺, Ca²⁺, Cl^-, and F^- were the key environmental factors significantly shaping the bacterial community structure. Conclusion Dolomite is abundant in the sediments of Jibuhulangtu Salt Lake. Its formation is likely attributable to the extremely high sulfate concentrations and high Mg/Ca ratio of the lake water, as well as the metabolic activities of key functional groups such as sulfate-reducing bacteria.

Objective In view of the issues of reservoir acidification and pipeline corrosion caused by sulfate-reducing bacteria (SRB) during oil and gas field development, this study focused on the green synthesis of silver nanoparticles with bamboo leaf extract and systematically evaluated their effectiveness and mechanism in inhibiting SRB. Methods Under alkaline conditions (pH 11.0) and at 80 ℃, silver nanoparticles with a particle size of 20-50 nm and good monodispersity were successfully prepared through ultrasonically assisted ethanol extraction of active substances from bamboo leaves. Results Real-time quantitative PCR results showed that 50 μg/mL of silver nanoparticles reduced the total bacterial count from 5.21×10⁹ copies/mL to 2.01×10⁷ copies/mL. Meanwhile, the abundance of sulfate-reducing functional genes dsrB and aprA decreased from 1.76×10⁹ copies/mL and 2.03×10⁹ copies/mL to undetectable levels. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay indicated that silver nanoparticles reduced SRB activity in a dose-dependent manner, with the SRB activity in the 50 μg/mL silver nanoparticles group decreasing to 40% of that in the control group. The lactate dehydrogenase (LDH) release assay confirmed that the cytotoxic effect of the synthesized silver nanoparticles ranged from 32.8% to 42.1%. Under SEM/TEM, silver nanoparticles were observed to adsorb onto the cell membrane surface, forming a nanoscale coating that altered membrane permeability and disrupted the cell wall structure. At a concentration of 50 μg/mL, silver nanoparticles completely inhibited biofilm formation. Core simulation experiments further validated the effective inhibition of SRB by the nanoparticles in reservoir environments, with hydrogen sulfide production decreasing from 83.16 mg/L to below the limit of detection. Conclusion This study demonstrates that bamboo leaf-mediated synthesized silver nanoparticles exhibit high efficiency in inhibiting SRB, environmental friendliness, and resistance to microbial drug resistance. It provides a green prevention and control strategy for microbial corrosion in oil and gas development processes.

Objective To isolate and identify secondary metabolites from the deep-sea-derived fungus Talaromyces muroii SCSIO 40439 and evaluate their biological activities. Methods The strain SCSIO 40439 was fermented on a rice medium. The resulting extract was subjected to silica gel column, Sephadex LH-20 column, and semipreparative high performance liquid chromatography (HPLC) to obtain compounds. Structure elucidation was performed via high-resolution electrospray ionization mass spectrum (HRESIMS), nuclear magnetic resonance (NMR), and X-ray crystal diffraction and comparison with literature data. Antimicrobial activity was assessed through the filter paper disk diffusion method, while tyrosinase inhibitory activity was measured based on the rate of dopamine oxidation. Results Four compounds were isolated from the fermentation extract of T. muroii SCSIO 40439, including a new orsellinic acid-cysteine dimer dioscysmycine A (1) and three known polyketides: alternariol (2), altenusin (3), and 3′-hydroxyalternariol 5-O-methyl ether (4). Compound 1 exhibited tyrosinase inhibitory activity with an inhibition rate of 58% (the positive control, kojic acid, showed an inhibition rate of 90%). Compound 2 inhibited the growth of Staphylococcus aureus ATCC 29213 and methicillin-resistant S. aureus ATCC 43300. Conclusion This study expands the known structural diversity of secondary metabolites of Talaromyces and identified a candidate inhibitor for tyrosinase. Furthermore, the findings provide a new biosynthetic gene cluster of alternariol.

Objective To investigate the differences in the structure and function of rhizosphere soil microbial communities between two dominant halophytes—Suaeda salsa and Phragmites australis—in Yuncheng Salt Lake Wetland and to reveal their associations with soil environmental factors, thereby providing a theoretical basis for the ecological restoration of saline-alkali wetlands. Methods Rhizosphere soil samples of S. salsa and P. australis, as well as bare beach soil sample without plant cover, were collected as research objects. Metagenomic sequencing was employed to analyze the microbial community structure and functional genes, and key soil physicochemical properties were determined. Results The total dissolved solids (TDS), pH, and Cl^- concentration in the rhizosphere soils of S. salsa and the bare beach were higher than those in the rhizosphere of P. australis (P<0.05). The microbial diversity and abundance in the rhizosphere soils of both plant species were significantly higher than those in the bare beach soil. The bare beach soil was significantly enriched with the viral phylum Cressdnaviricota, while the rhizosphere soil of S. salsa was significantly enriched with the psychrophilic genus Algoriphagus. Both the rhizosphere soil of S. salsa and the bare beach soil showed co-enrichment of the genera Halomonas and Salegentibacter. TDS was the key factor driving the structures and functional distribution of soil microbial communities, with a contribution rate of 64.40%. Compared with the bare beach, the plant rhizospheres significantly increased the abundance of functional genes related to carbon (e.g., acdB and acs), nitrogen (e.g., gdh_K15371 and nasA), and sulfur (e.g., sudA and dmdB) cycling. Conclusion S. salsa and P. australis shape distinct rhizosphere microenvironments through different survival strategies, which enhance microbial diversity and the abundance of functional genes associated with element cycling, thereby improving the stability and functioning of the saline-alkali wetland ecosystem. This study provides a theoretical foundation for utilizing plant-microbe interactions in the bioremediation and sustainable agricultural use of saline-alkali land.

Objective To determine the composition, diversity, functional metabolic characteristics, and their association with environmental factors of the microbial community in Xiaochaidan Salt Lake, and to evaluate its ecological functions and potential risk as a reservoir for antibiotic resistance genes (ARGs). Methods Metagenomic sequencing was applied to water-sediment mixed samples from the lake. Databases including non-redundant protein database (NR), clusters of orthologous groups of proteins (COG), Kyoto encyclopedia of genes and genomes (KEGG), carbohydrate-active enzymes database (CAZy), and comprehensive antibiotic resistance database (CARD) were used to annotate microbial taxonomy, functional genes, metabolic pathways, and ARGs. Additionally, Hellinger transformation-based principal component analysis (tb-PCA) was conducted to link microbial community structures with environmental factors. Results The salt lake exhibited high microbial diversity (Shannon index: 5.620-6.112), with a total of 16 850 identified species. Bacteria dominated the microbial community (relative abundance of 91.89%), mainly represented by Pseudomonadota (57.22%) and Bacteroidota (14.64%). Archaea (3.77%) were absolutely dominated by Euryarchaeota (92.64%). Siphoviridae and saprotrophic Oomycetes were the most dominant taxa in the viral and eukaryotic communities, respectively. Association analysis with environmental factors demonstrated that bacterial distribution was primarily driven by Cl^-, whereas archaeal community distribution was co-driven by Na⁺, Cl^-, and SO₄^2-. Metabolic functions related to amino acid and carbohydrate metabolism were highly active, as reflected by the enrichment of glycosyltransferase and glycoside hydrolase genes. Notably, diverse ARGs were detected, which were primarily conferred by efflux pump systems (e.g., novA). Conclusion Xiaochaidan Salt Lake harbors a complex and functionally synergistic microbial ecosystem. Local differences in ionic concentrations represent the primary driver of niche differentiation between bacteria and archaea. To adapt to this extreme habitat, indigenous microbes have evolved a strategy that integrates conservative osmoregulation and flexible carbon metabolism. The high abundance of efflux pump-associated ARGs implies that this hypersaline lake serves as a natural reservoir for ARGs, underscoring the potential risk of their ecological dissemination.

Objectives To screen copper-resistant and copper-reducing bacteria from deep-sea hydrothermal sediments and systematically analyze Cu(II) bioreduction process mediated by the bacteria, and mineralization product characteristics, thus filling the knowledge gap regarding microbial participation in copper cycling in deep-sea hydrothermal environments. Methods A strain, Shewanella sp. FeAMO, was obtained through anaerobic enrichment culture. With sodium lactate as the electron donor and Cu(II) as the terminal electron acceptor, inductively coupled plasma mass spectrometry, scanning electron microscopy-energy dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were employed to analyze bacterial growth, copper reduction kinetics, and physicochemical properties of the products. Results Strain FeAMO exhibited high tolerance to 400 μmol/L Cu(II), achieving a Cu(II) removal rate of 96.8% within 72 h. The mineralization products were spherical microspheres with diameters ranging from 5 to 10 µm. The bulk phase was predominant crystalline cuprous sulfide (Cu₂S), while the surface was stably enriched with metallic copper (Cu⁰) nanoparticles, forming a core-shell heterostructure. Conclusion Shewanella sp. FeAMO can tolerate Cu(II) with copper transporters and generate Cu₂S-Cu⁰ composite minerals by coupling copper reduction and sulfur reduction pathways. This study not only elucidates the mechanism of microbial-driven copper and sulfur cycling in hydrothermal environments but also provides a potential strategy for heavy metal immobilization and resource recovery.