Maize, an important food crop in China, directly affects national food security. In recent years, due to climate change and shifts in farming practices, maize stalk rot has become a major threat to maize production in China. [Objective] To screen and identify biocontrol bacterial strains against maize stalk rot, determine their optimal fermentation process, and develop effective bacterial agents, thereby providing theoretical support and a material basis for constructing a novel green prevention and control technology system. [Methods] Antagonistic bacterial strains against Fusarium graminearum were screened through a combination of dilution coating and plate confrontation methods. Candidate strains were identified through molecular biological techniques combined with physiological and biochemical characterization. Fermentation conditions were optimized via single-factor experiments, and seed coating agents were developed with the selected biocontrol bacteria. Indoor pot experiments and outdoor field plot trials were carried out for the biocontrol bacteria to systematically evaluate their maize growth-promoting effects and control efficacy against maize stalk rot. [Results] Two biocontrol strains, HS104 and HS107, with inhibition rates of approximately 70.00% against F. graminearum, were successfully screened out and identified as Bacillus velezensis. Both strains exhibited broad-spectrum antagonistic activity against major maize pathogens, including F. verticillioides, F. oxysporum, and Bipolaris maydis, with inhibition rates of around 60.00%. After optimization of fermentation conditions, indoor pot experiments showed that HS104 and HS107 not only significantly promoted maize growth but also achieved the control efficacy of 75.00% and 71.00% against maize stalk rot, respectively. The seed coating agents developed with the selected biocontrol bacteria performed well in field trials, significantly promoting maize growth and achieving the control efficacy of 63.93% and 77.33% against maize stalk rot, respectively. Moreover, they increased the yield of susceptible plants by 8.20% and 9.20%, respectively, compared with the control. [Conclusion] Strains HS104 and HS107 possess multiple excellent traits, including broad-spectrum antifungal activity, strong plant growth-promoting effects, and high disease control efficacy, demonstrating broad application prospects in the biocontrol of maize stalk rot and the enhancement of crop yields.

As an important grain production base and the main maize-producing area in China, the black soil region in northeast China can utilize multifunctional plant growth-promoting rhizobacteria (PGPR) to convert nitrogen and phosphorus into plant-available forms through nitrogen fixation and phosphate solubilization, thereby reducing chemical fertilizer input and promoting crop growth. [Objective] To systematically screen efficient multifunctional strains from the black soil in northeast China and evaluate their effects on soil fertility and maize growth under 20% nitrogen and phosphorus reduction through low-temperature (16 ℃) germination and pot experiments, thus providing excellent strain resources for developing microbial inoculants adapted to the black soil region in northeast China. [Methods] Functional strains were isolated from rice rhizosphere soil via selective media and identified by 16S rRNA gene sequence analysis. The plant growth-promoting traits of the obtained strains, including nitrogen fixation, phosphate solubilization, and indole-3-acetic acid (IAA) production, were quantitatively determined. Furthermore, maize seed germination and pot experiments were carried out to systematically evaluate the effects of these functional strains on seed germination under low-temperature conditions (16 ℃), as well as on soil physicochemical properties and seedling growth indicators during the seedling stage, on the basis of which the potential of functional strains in improving soil quality and promoting crop growth was comprehensively evaluated. [Results] Two PGPR strains, Niveispirillum sp. YM6 and Bacillus sp. A03, were screened from rhizosphere soil and identified by 16S rRNA gene sequence analysis. Functional characterization revealed that strain YM6 exhibited both nitrogen fixation and indole-3-acetic acid (IAA) production capabilities, while strain A03 displayed both phosphate solubilization and IAA production capabilities. Under low-temperature (16 ℃) conditions, inoculation with both YM6 and A03 achieved the best performance in promoting seed germination, with a germination rate of 49.00%, a germination index 51.44% higher than the control, and shortening of 0.18 d in the average germination time, demonstrating a synergistic growth-promoting effect superior to both single-strain treatments and ternary combinations. Pot experiments further demonstrated that compared with the reduced-fertilizer control (CK-R), the ternary combination YM6+A03+ZP (Penicillium bilaiae) significantly increased the maize plant height, total biomass, total chlorophyll content, and soil available phosphorus and ammonium nitrogen by 12.73%, 82.60%, 66.30%, 29.94%, and 30.03%, respectively. Notably, the binary combination YM6+A03 showed no significant difference from the full-fertilizer control (CK-F) in these indicators but increased them by 9.08%, 63.54%, 32.81%, 21.51%, and 15.31%, respectively, compared with CK-R, outperforming all single-strain treatments. These results indicated that YM6+A03+ZP exhibited a significant synergistic enhancement effect, capable of maintaining or even improving crop productivity under chemical fertilizer reduction. [Conclusion] Single-strain inoculation exhibited limited plant growth-promoting effects. The binary combination YM6+A03 under 20% reduced fertilization maintained crop productivity comparable to that of CK-F, whereas the ternary combination YM6+A03+ZP significantly outperformed CK-F in promoting maize growth while improving black soil nutrient status, holding promise for the development of region-specific microbial inoculants adapted to the black soil region in northeast China.

[Objective] To investigate the effects of planting patterns on the soil physicochemical properties and microbial community structures of Polygonatum cyrtonema Hua. [Methods] With the soil of wild P. cyrtonema as the control, the soil samples from P. cyrtonema grown under monocropping and rotation patterns were collected as the research subjects. The structural and functional characteristics of soil microbial communities under wild, monocropping, and rotation patterns were analyzed by Illumina MiSeq PE300 high-throughput sequencing. [Results] Compared with the control, monocropping and rotation significantly increased the biomass of P. cyrtonema and the polysaccharide content in the rhizomes. Compared with monocropping, rotation increased soil ammonium nitrogen (AN) by 37.96% and enhanced the activities of sucrase (SC), acid phosphatase (ACP), and urease (UE) by 63.15%, 58.72%, and 73.03%, respectively, and it exhibited neutral soil pH. The control and monocropping resulted in higher Shannon and Chao1 indices for both bacterial and fungal communities in the soil (P<0.05). Planting patterns significantly affected the structures of bacterial and fungal communities in the soil. Different planting patterns showed variations in the relative abundance of the dominant bacterial phyla Pseudomonadota, Actinomycetota, Acidobacteriota, and Chloroflexota as well as the dominant fungal phyla Ascomycota and Mortierellomycota (P<0.05). The relative abundance of Pseudomonadota, Actinobacteria, Ascomycota, and Mortierellomycota was the highest under rotation. Additionally, rotation increased the relative abundance of beneficial fungal genera, including Saitozyma, Podila, Mortierella, and Trichoderma. Correlation and redundancy analyses revealed that microbial community changes were correlated with soil pH as well as AN, UE, ACP, and SC activities (P<0.05). Functional prediction indicated that nitrogen fixation and ureolysis were the dominant bacterial functions under rotational cropping. FUNGuild analysis demonstrated that functions associated with ectomycorrhizal fungi and litter saprotrophs were significantly enriched in the rotation soil. [Conclusion] Monocropping and rotation change the structures and functions of bacterial and fungal communities in the soil of P. cyrtonema. Rotation enhances the activities of UE, ACP, and SC and increases the abundance of beneficial fungi in the soil and improves the polysaccharide content and biomass of P. cyrtonema, thus being conducive to seedling cultivation.

[Objective] To investigate the effects of partially substituting chemical fertilizer with bio-organic fertilizer on the structure and function of soil microbial communities in wheat fields, thus providing a theoretical basis and technical support for fertilizer reduction and efficiency improvement in wheat production. [Methods] This study compared three treatments—conventional chemical fertilizer (CF), partial substitution of chemical fertilizer with organic fertilizer (OF), and partial substitution of chemical fertilizer with bio-organic fertilizer (BOF)—with respect to soil physicochemical properties, microbial community structure and function, community assembly mechanisms at the wheat jointing stage, and plant growth traits at the harvest stage. [Results] Compared with CF, BOF increased the biomass by 33.33% (P<0.05). Compared with CF, BOF increased soil organic matter, available phosphorus, available potassium, sucrase activity, and urease activity by 29.82%, 35.13%, 5.32%, 14.93%, and 36.18%, respectively. Compared with OF, BOF showed the corresponding increases of 3.29%, 133.73%, 47.21%, 19.58%, and 14.78%, respectively. The soil quality index ranked as BOF>OF>CF. Microbial community analysis showed that BOF significantly increased the abundance of beneficial taxa such as RB41, Massilia, Mortierella, and Cystofilobasidium, while reducing the abundance of potentially pathogenic fungi such as Fusarium and Aspergillus and enhancing the complexity and connectivity of the molecular ecological network. Functional prediction indicated that compared with CF, OF and BOF increased potential carbon metabolic functions such as aerobic chemoheterotrophy and aromatic compound degradation. In addition, BOF enhanced the potential function of ureolysis while suppressing the potential function of nitrate reduction. [Conclusion] By comparing the comprehensive effects of different fertilization combinations, we found that BOF significantly improves soil nutrient status and enzyme activities at the wheat jointing stage and optimizes the microbial community structure and ecological network, thereby providing favorable soil fertility conditions for plant growth. This study lays a theoretical foundation for optimizing fertilization structure and reducing chemical fertilizer use while improving efficiency.

Cereibacter azotoformans has been widely applied in the water quality regulation and disease prevention of aquaculture owing to its efficient nitrogen and phosphorus removal capacity as well as its probiotic effects on aquatic animals. However, whether this bacterium possesses both capabilities of denitrification and polyphosphate accumulation (DPA) remains unclear. [Objective] To identify the DPA phenotype of C. azotoformans and to elucidate its underlying molecular regulation mechanism. [Methods] Using the C. azotoformans strain ATCC 17025 as a model, we first examined its metabolic characteristics under DPA-inducing conditions to determine the presence of a DPA phenotype. Subsequently, gene deletion, DNA affinity purification sequencing (DAP-seq), and physiological and biochemical analyses were employed to systematically investigate the regulatory role of the NtrX/Y two-component system in DPA of the model strain. [Results] The C. azotoformans strain exhibited a typical DPA phenotype: releasing phosphate during the anaerobic stage and excessively absorbing phosphate in synergy with denitrification during the anoxic stage. At the end of the experiment, the nitrate degradation rate reached 95%, and the phosphate removal rate exceeded 90%. The deletion of ntrY resulted in the loss of the DPA phenotype. Particularly, the environmental phosphate concentration continuously increased rather than decreased, and the peak synthesis of intracellular polyhydroxyalkanoates (PHAs) was significantly impaired compared with that of the wild type (0.11 mg/mL). DAP-seq analysis revealed that NtrX directly targeted key denitrification genes (nirK and norB/C) as well as the PHAs synthesis gene phaC, thereby coordinately regulating denitrification and polyphosphate metabolism. [Conclusion] This study demonstrates that the anoxygenic phototrophic bacterium C. azotoformans possesses excellent DPA capabilities, and it reveals a central regulatory role of the NtrX/Y two-component system in this process. These findings offer a new theoretical basis for the development of microbial resources for simultaneous nitrogen and phosphorus removal.

[Objective] To isolate and screen the algicidal strains from samples of a eutrophic water body and study their algicidal characteristics and mode against Microcystis aeruginosa, thus providing a theoretical basis for the biological control of cyanobacterial bloom. [Methods] Strain identification was performed through morphological observation, physiological and biochemical tests, 16S rRNA gene sequence analysis, whole-genome sequencing, and average nucleotide identity (ANI) analysis. The algicidal effects under different inoculation amounts, bacterial growth phases, and initial algal densities were investigated. The algicidal mode was clarified by comparing the algicidal efficiency of cell-free filtrate and cell resuspension of the strain. The morphology of algal cells was explored by means of scanning electron microscopy (SEM). In addition, changes in physiological characteristics of algal cells were investigated through three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy. GC-MS was employed to identify the major algicidal substances after n-hexane extraction. [Results] A highly efficient algicidal strain L2 was obtained and identified as Bacillus velezensis (CGMCC No. 38496, GenBank accession No. PP693440). At an inoculation amount of 10%, the strain achieved the algal inhibition rate of 89.35% against M. aeruginosa after seven days. The algal inhibition rates of the cell-free filtrate and fermentation broth of L2 were 90.51% and 91.75% after seven days, respectively. While the algal inhibition rate of the cell suspension was only 15.10%. This phenomenon indicated that L2 indirectly inactivated M. aeruginosa by secreting extracellular active substances. The major algicidal substances secreted by strain L2 were identified as fatty amides and cyclic dipeptides. Algal cells exhibited shrinkage and surface roughening, with significantly decreased phycobiliprotein content during the algicidal process. In addition, the composition of extracellular organic matter shifted from protein-like substances to humic-like substances. [Conclusion] B. velezensis L2 exhibits high algicidal activity against M. aeruginosa. Algal cells are inactivated primarily through the indirect mode of extracellular substance secretion, which cause damage to the morphology of algae cells and inhibit the activity of the photosynthetic system. The strain L2 exhibits good potential for the biological control of cyanobacterial bloom.

[Objective] To elucidate the physiological and biochemical mechanisms of iron release from bacterioferritin (Bfr) in Agrobacterium fabrum, identify the physiological reductant that provides electrons for the iron release from Bfr in cells, and determine whether Bfr-associated ferredoxin (Bfd) is required to facilitate electron transfer from the reductant to Bfr, thereby exploring a new approach to inhibit the iron release from Bfr and further disrupt intracellular iron homeostasis as well as impair A. fabrum growth and proliferation. [Methods] Bioinformatics analysis was carried out to identify the gene encoding Bfd-like protein in the A. fabrum genome. Bfr and the predicted Bfd were heterologously expressed and the obtained proteins were purified. In vitro assays were conducted to determine whether the predicted Bfd could assist the physiological reductant in transferring electrons to Bfr. Subsequently, we knocked out the Bfd-encoding gene to assess the impacts of Bfd on the iron release of Bfr and A. fabrum growth at the cellular level. [Results] The A. fabrum gene ATU_RS13485 encoded a (2Fe-2S)-binding protein containing the conserved amino acid motif (…C-X-C…C-X₂-C…) existent in Bfd proteins, confirming it as the Bfd of A. fabrum. Purified recombinant Bfd was able to assist FADH₂ in delivering electrons to Bfr in vitro, triggering the release of Fe²⁺ from mineralized A. fabrum Bfr. Upon bfd knockout, intracellular Bfr iron release of A. fabrum was severely impaired, and A. fabrum growth was significantly affected. [Conclusion] ATU_RS13485 encodes the Bfd of A. fabrum. A. fabrum Bfr requires Bfd to utilize electrons from the physiological reductant FADH₂ for iron release. The absence of Bfd blocks iron release from Bfr and impairs A. fabrum growth, which suggests that designing inhibitors to disrupt the Bfr-Bfd interaction may offer a promising strategy for controlling crown gall disease caused by A. fabrum.

[Objective] As a key component of eukaryotic chromatin, histone variant H2A.Z plays an important role in gene expression regulation. This study explored the regulatory effects of H2A.Z on the biological characteristics and pathogenicity of Fusarium graminearum, aiming to decipher its epigenetic regulation mechanism in the pathogenicity of pathogenic fungi. [Methods] The genome of F. graminearum was excavated by bioinformatics methods, and the H2A.Z homologous genes were identified by multiple sequence alignment and phylogenetic analysis. The gene deletion mutants were constructed by homologous recombination combined with PEG-mediated protoplast transformation. The phenotypic differences in morphological development, pathogenicity, and environmental adaptability between the wild type and the mutants were systematically evaluated by morphological observation, pathogenicity determination, and abiotic stress response experiments. [Results] H2A.Z was encoded by FgHTZ1. Phenotypic analysis showed that the deletion of FgHTZ1 resulted in significant retardation of colony growth, abnormal mycelial polar growth and conidial morphogenesis, and significant attenuation in pathogenicity. In addition, the mutants showed significantly altered sensitivity to osmotic stress (NaCl and sorbitol), oxidative stress (H₂O₂), and cell wall damage (Congo red), exhibiting a complex phenotype of enhanced tolerance to cell wall disruptors but hypersensitivity to osmotic/oxidative stress. [Conclusion] FgHTZ1 is the coding gene of H2A.Z in F. graminearum. As a positive regulator, this gene not only regulates the vegetative growth, morphological development, and pathogenicity of F. graminearum but also participates in mediating osmotic stress and oxidative stress responses, playing a key role in maintaining cell wall integrity. This study provides an important theoretical basis for further understanding the molecular functions of histone variants in the pathogenic mechanisms of plant pathogenic fungi.

[Objectives] To investigate the effects of early fructo-oligosaccharide (FOS) intervention on the antioxidant capacity, colonic barrier function, and colonic microbiota and metabolites in suckling piglets. [Methods] A total of six litters (10 piglets per litter) of Duroc×Landrace×Yorkshire newborn piglets were selected. Within-litter grouping was adopted with equal average body weight per group: five piglets from each litter were assigned to the control group (CON), and the other five formed the experimental group (Fos). From the second day after birth, the Fos group received daily oral administration of a FOS solution at an effective dose of 3 g/d per piglet, while the control group received an equal volume of normal saline. The trial lasted for 21 days. [Results] Early FOS intervention reduced the total cholesterol level and increased the concentrations of urea nitrogen, total protein, and albumin in the serum samples of suckling piglets (P<0.05). Early FOS intervention enhanced the total antioxidant capacity and glutathione peroxidase activity (P<0.05), while reducing the malondialdehyde content (P<0.05) in the serum. In addition, it enhanced the catalase activity and decreased the malondialdehyde content in the colonic mucosa (P<0.05). Early FOS intervention decreased the diamine oxidase (DAO) level in the serum (P<0.05), increased the DAO and D-lactic acid levels in the colonic mucosa (P<0.05), and up-regulated the expression of colonic barrier function-related genes (Claudin-1, ZO-1, Occludin, MUC1, MUC2, and MUC4) (P<0.05). Early FOS intervention improved the alpha diversity indexes of colonic bacteria (P<0.05) and induced separation of microbiota in colonic chyme of 14- and 21-day-old piglets (P<0.05). It altered the composition of colonic chyme microbiota at both phylum and genus levels (P<0.05). Furthermore, early FOS intervention increased the concentrations of lactic acid and short-chain fatty acids in the colon of suckling piglets (P<0.05). [Conclusions] Early FOS intervention enhances the antioxidant capacity, upregulates the mRNA levels of colonic barrier function-related genes, modulates the colonic microbiota, and promotes the production of lactic acid and short-chain fatty acids in suckling piglets.

[Objective] To investigate whether gut microbiota (GM) reshaped by exercise can ameliorate chronic unpredictable mild stress (CUMS)-induced depressive-like behaviors in mice via fecal microbiota transplantation (FMT), and to explore the underlying mechanisms. [Methods] Twenty SPF-grade male C57BL/6J mice (four weeks old) meeting the experimental criteria were randomly assigned to a control group (CON, n=5), a model group (CUMS, n=10), and an exercise group (SW, n=5). After four weeks of CUMS modeling, mice in the model group were further randomized into a PBS control group (CUMS+PBS, n=5) and an FMT group (CUMS+FMT, n=5). The latter received GM transplants from SW donors, and the experiment lasted for eight weeks. Depressive-like phenotypes were assessed by behavioral tests. GM composition was analyzed by 16S rRNA gene sequencing. Hippocampal and colonic structures were examined by histopathological staining. Hippocampal inflammatory cytokine expression was measured by quantitative real-time PCR (qPCR). Correlation analyses were performed between differential microbial taxa and environmental factors. [Results] Compared with the CON group, the model group exhibited typical depressive-like behaviors and disrupted GM structure, characterized by a decreased Bacteroidota/Bacillota ratio and enrichment of the pro-inflammatory genus Adlercreutzia. The SW group showed increased GM richness (P<0.05) and reversed behavioral abnormalities. After FMT intervention, depressive-like behaviors in recipient mice were markedly alleviated, indicated by an increased sucrose preference rate (P<0.000 1) and reduced immobility time in the forced swim test (P<0.01). Furthermore, hippocampal neuronal injury and colonic barrier disruption were effectively repaired. Microbiota analysis revealed that FMT restored GM diversity in recipients (P<0.01), shifted the microbiota structure toward that of the CON group, significantly reduced the relative abundance of Adlercreutzia, and increased the relative abundance of beneficial genera such as Candidatus_Saccharimonas and Alistipes. From a mechanism perspective, FMT suppressed the CUMS-activated nucleotide-binding and oligomerization domain (NOD)-like receptor signaling pathway and downregulated hippocampal mRNA levels of NOD-like receptor family pyrin domain containing 3 (NLRP3) and interleukin-18 (IL-18) (P<0.01). Correlation analysis further confirmed that the abundance of beneficial genera was positively correlated with positive behavioral indices and negatively correlated with pro-inflammatory cytokine expression. [Conclusion] Exercise can attenuate CUMS-induced depressive-like behaviors by reshaping the GM and inhibiting NOD-like receptor signaling pathway-mediated neuroinflammation, and this protective effect can be effectively transferred via FMT.