Acidic soil accounts for approximately 50% of the world’s available arable land. Its highly active aluminum ions and low pH environment not only directly inhibit plant growth but also significantly alter the microbial community structure in the rhizosphere, weaken the functions of beneficial microorganisms, and exacerbate soil-borne diseases. Brassinolide (BR), as a group of important plant signaling molecules, play a core role in enhancing the plant stress resistance in acidic soil by precisely regulating plant-microorganism interactions. BR promote the root secretion of organic acids such as malic acid and oxalic acid by activating BZR1/BES1 and transcription factors. These secretions act as carbon sources and chemotactic signals to specifically recruit beneficial microorganisms such as Paenibacillus azotofixans, Pseudomonas, and ectomycorrhizal fungi, reshaping the microbial community structure in the rhizosphere. The microbial community reassembly induced by BR significantly enhances aluminum ion chelation, nutrient activation, and pathogen inhibition. For instance, nitrogen-fixing bacteria enriched utilize malic acid for metabolic activities and secrete auxin and other substances to promote plant growth in acidic environments. Ectomycorrhizal fungi alleviate aluminum toxicity through oxalic acid secretion. Meanwhile, BR, in collaboration with plant hormones such as auxin and gibberellin, optimizes the root structure, expands the microbial colonization niche, and forms a complex synergistic network for enhancing stress resistance. Future research should focus on the specific regulatory mechanisms of BR on the rhizosphere microbiome, unveil the direct action pathways of BR as microbial signaling molecules, and develop efficient BR-microbial compound preparations in combination with microbial community engineering, providing innovative strategies and application solutions for the regulation of acidic soil microorganisms.

Objective To investigate the changes in microbial community structure and function in degraded mangrove sediment, and to explore their potential relationships with environmental factors and mangrove degradation. Methods Sedimental samples were collected from degraded mangroves in Guangxi Beihai Coastal National Wetland Park, marked as healthy (ZC), early-stage/deteriorating (BY), and necrotic (SW) groups. The physicochemical factors, including total nitrogen (TN), total phosphorus (TP), total organic carbon (TOC), oils, and various heavy metals, were analyzed using standard methods. High-throughput sequencing of 16S rRNA gene and ITS region was performed. Subsequent analyses, including diversity indices, Venn plot, LEfSe analysis, Z_i-P_i analysis, and FAPROTAX/FUNGuild functional prediction, were employed to compare the composition and functional differences of bacterial and fungal communities and to identify their driving environmental factors. Results The richness and diversity of the bacterial community followed the order of SW>ZC≈BY. The dominant phyla were Pseudomonadota and Chloroflexi. In contrast, fungal richness and diversity were lowest in SW, where Ascomycota was the dominant phylum. LEfSe analysis indicated that the bacterial community in ZC was characterized by Actinomycetota and several Desulfobacterota; BY was enriched in Gemmatimonadota; SW was dominated by Bacillota, Campylobacterota, and Spirochaetota. Z_i-P_i analysis revealed that keystone fungal taxa in BY were mainly from Ascomycota, while those in SW contained both Ascomycota and Basidiomycota. Functional prediction suggested that bacterial communities were predominantly chemoheterotrophic, with fermentation as a major pathway. Fungal communities were primarily saprotrophic and notably pathogenic. Correlation analysis further demonstrated that TN, TP, oils, and heavy metals (e.g., As, Cu) significantly influenced microbial community structure. Conclusion By investigating microbial community structure and function, this study elucidates the dynamic response of microbial communities to environmental shifts in degrading mangrove ecosystems, thus providing a crucial microbiological reference for future ecosystem health assessment and restoration efforts.

Global climate change and soil heavy metal pollution have raised higher requirements for the synergistic adaptability of conventional remediation technologies. Microbially induced carbonate precipitation (MICP) technology, with its unique biological metabolism and environmental interaction characteristics, provides a new pathway for the synergistic management of carbon sequestration and heavy metal stabilization. This technology induces calcium carbonate formation through two core enzyme-mediated pathways involving urease and carbonic anhydrase, enabling simultaneous CO₂ sequestration by mineralization and heavy metal immobilization. In carbon sequestration scenarios, MICP technology can enhance the geological stability of carbon sequestration sites through lithological improvement and strengthen carbon sequestration efficiency through high-efficiency mineralization reactions. In heavy metal remediation scenarios, it can achieve heavy metal stabilization through multiple mechanisms such as adsorption, co-precipitation, and surface complexation, and different calcium carbonate crystal forms can adapt to varied pollution scenarios. However, the large-scale application of MICP technology currently faces three major bottlenecks: insufficient tolerance of functional strains to extreme environments, compatibility conflicts between exogenous strains and native ecosystems, and coupling barriers between metabolic pathways for carbon sequestration and heavy metal immobilization. To address these issues, this paper proposes a three-stage synergistic process flow hypothesis for heavy metal immobilization, carbon sequestration by mineralization and long-term monitoring. Sequentially switching metabolic pathways theoretically resolves the pH requirement conflict between heavy metal immobilization and carbon sequestration by mineralization, providing new solutions for the engineering application of MICP technology. Future research should focus on the modification of functional strains for extreme habitats, regulation of interactions between exogenous and native microorganisms, and precise optimization of process parameters, to advance this synergistic model from theoretical design to on-site validation, providing technical support for achieving carbon neutrality and the safe utilization of polluted soils.

Objective Coastal wetlands are important natural sources of nitrous oxide (N₂O), and the distribution of denitrification genes nirS and nirK directly influences their N₂O emission potential. Vegetation types can significantly regulate the abundance of these genes by altering soil physicochemical properties and carbon-nitrogen availability, while the underlying mechanisms remain unclear. Methods Soils were collected from five representative habitats—Kandelia obovata (mangrove), Spartina alterniflora, Cyperus malaccensis, Phragmites australis, and unvegetated mudflat—in the Minjiang River estuary wetland at depths of 0-10, 10-20, and 20-30 cm. The abundance of nirS and nirK was quantified by real-time quantitative PCR, and their environmental drivers were analyzed through random forest modeling and correlation analysis. Results The abundance of nirS and nirK in all the vegetated soils was significantly higher than that in the unvegetated mudflat, with the highest values observed in the surface soil (0-10 cm) under P. australis. Both genes showed significantly decreased abundance as the soil depth increased, presenting a distinct surface enrichment effect. The nirS/nirK ratio was greater than 5 across all soil samples, indicating the dominance of nirS-type denitrifiers. The mangrove surface soil exhibited the highest nirS/nirK ratio, likely due to low dissolved organic carbon (DOC) levels limiting nirK-type denitrifiers. Random forest analysis identified soil electrical conductivity as the primary driver of nirS and nirK abundance, while available phosphorus (AP) was the dominant factor influencing the nirS/nirK ratio. High salinity promoted the enrichment of both genes, whereas high AP concentrations increased the nirS/nirK ratio. Conclusion Vegetation type and soil depth jointly shape the distribution patterns of nitrite reductase genes in the Minjiang River estuary wetland by regulating soil salinity, DOC, and nutrient availability. The results provide insights for nitrogen cycle management in coastal wetlands.

Mangrove ecosystems, situated at the land-sea interface, serve as vital blue carbon sinks, playing a key role in the global carbon cycle and climate regulation with their efficient carbon sequestration capacity. Microorganisms are central drivers of carbon sequestration in mangrove sediments, capable of fixing carbon through diverse metabolic pathways. This review first summarizes the currently identified microbial carbon fixation pathways and carbon sequestration mechanisms in mangrove sediments, with a focus on three primary processes: the Calvin-Benson-Bassham cycle, the reductive tricarboxylic acid cycle, and the reductive acetyl-CoA (Wood-Ljungdahl) pathway. Furthermore, we discuss the influences of key environmental factors, such as vegetation type, sediment physicochemical properties, and nutrient inputs, on microbial carbon fixation and sequestration. Finally, we propose the future directions for studies on microbial carbon fixation and sequestration in mangrove sediments, including the couplings of nutrient cycling processes, microbiome engineering, and microorganism-plant interactions. This review proposes potential novel strategies for enhancing blue carbon capacity in mangrove ecosystems.

Objective To screen the microbial strains capable of efficiently activating soil cadmium, addressing the technical bottleneck of low efficiency in cadmium-contaminated soil remediation by hyperaccumulators. Methods Farmland soils with potential Cd contamination were collected from various locations in Hunan Province. Acid-producing bacteria were initially screened via the bromocresol purple discoloration method. The pH of the fermentation broth, cadmium chloride tolerance, and cadmium carbonate activation capacity were compared among strains to identify dominant strains, which were then subjected to species identification. On this basis, bacterial strains with application potential were further screened. The desorption effect of the selected strain on soil cadmium under different carbon and nitrogen sources was investigated through shake flask experiments. Pot experiments were carried out to analyze the activation effect on soil cadmium under different nutrient conditions. Results A total of 372 acid-producing bacterial strains were isolated via the bromocresol purple discoloration method. Through comprehensive screening based on the ratio of the discoloration zone diameter (D) to the colony diameter (d) on solid plates, fermentation broth pH, cadmium chloride tolerance, and cadmium carbonate activation assays, four elite strains, designated HT-B1, HTQ-B1, QBS-B2, and MY-B1, were selected. They were identified as Staphylococcus epidermidis, Staphylococcus hominis, Priestia megaterium, and Acinetobacter sp., respectively, based on molecular evidence. In accordance with microbial fertilizer safety standards, strain QBS-B2 was prioritized for further study. This strain exhibited a minimum fermentation broth pH of 3.65 and achieved a cadmium carbonate activation rate of 92.27%. Culture with glucose as the carbon source and ammonium chloride as the nitrogen source were found to be optimal for enhancing cadmium desorption from soil by strain QBS-B2. Under these conditions, the soluble cadmium concentration reached 170.77 μg/L, which was 66.5 times higher than that of the control group, corresponding to a soil cadmium desorption rate of 46.21%. Furthermore, strain QBS-B2 significantly increased the content of available cadmium and available phosphorus in the soil. The application of compound fertilizer enhanced the cadmium activation of QBS-B2, resulting in a soil cadmium activation rate of 17.37%. The application of organic fertilizer significantly promoted the colonization and growth of the strain in the soil and increased the available phosphorus content by 5.9 times compared with the control. Conclusion This study provides elite microbial resources for the development of cadmium-activating microbial inoculants and bio-organic fertilizers based on P. megaterium QBS-B2. Furthermore, it establishes a theoretical foundation and demonstrates application potential for bio-augmented phytoextraction in the remediation of cadmium-contaminated soils.

An oilfield has entered the stage of high water-cut development, and the conventional water flooding effect is declining. It is urgent to develop microbial enhanced oil recovery (MEOR) technology to tap the remaining oil. Objective To analyze the indigenous bacterial community characteristics of different oil reservoirs and identify the indigenous oil-displacing bacteria, thus providing a scientific basis for the activation-type MEOR involving indigenous bacteria. Methods Produced fluid samples were collected from three high water-cut reservoirs (K₁h₂, J₂x, and J₂t). The 16S rRNA gene high-throughput sequencing combined with alpha diversity analysis, beta diversity analysis, linear discriminant analysis effect size (LEfSe)-based differential species identification, and canonical correlation analysis (CCA) of environmental factor correlations was employed to systematically reveal the bacterial community structure and analyze its driving mechanism. Additionally, the oil-displacement potential of the indigenous strain was assessed by core flooding test. Results A total of 174 OTUs were shared among the three groups, while the community composition was significantly different. Temperature, salinity, and water content were the main environmental influencing factors. The K₁h₂ group demonstrated prominent diversity, mainly consisting of bacteria with the potential to produce biosurfactants, such as Pseudomonas and unclassified_f_Rhodobacteraceae. The J₂x group enriched salt-tolerant hydrocarbon-degrading Marinobacter and significantly enriched sulfate-reducing groups. The J₂t group was dominated by thermophilic hydrocarbon-degrading bacteria such as Tepidiphilus and Burkholderiales. Core flooding test indicated that P. aeruginosa LD8 isolated from the K₁h₂ reservoir increased the oil recovery by 9.61% in the simulated reservoir environment. Conclusion The differences in physicochemical and microbial environments among different reservoirs emphasize the necessity of developing particular MEOR strategies. This study provides a research basis for the targeted activation of dominant oil-displacing bacteria, the avoidance of corrosion risks, and the optimization of on-site implementation plans.

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.

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.