Objective To investigate the effects of the antidepressant mirtazapine on the microbial resistome in complex intestinal environments. Methods We employed read mapping and metagenomic assembly to analyze the antibiotic resistance genes (ARGs) and their bacterial hosts based on metagenomic sequencing data of fecal and cecal content samples. Results A total of 29 classes of ARGs, comprising 610 subtypes, were identified. Bacitracin-, tetracycline-, and vancomycin-class ARGs were the predominant types. Chronic restrain stress (CRS) increased the total abundance of ARGs, significantly elevating the abundance of high-risk ARGs belonging to aminoglycoside, MLS (macrolide-lincosamide-streptogramin), and tetracycline classes (e.g., tetM, tetO, and tet40). Oral administration of mirtazapine exhibited initial microbiota-dependent effects on the resistome. It increased the total abundance of ARGs in healthy rats but decreased that in depressed rats. In addition, mirtazapine significantly enhanced the abundance of vancomycin-, aminoglycoside-, and mupirocin-class ARGs in healthy rats, as well as the tetracycline resistance gene tetP and multidrug resistance gene ompR in depressed rats. Bacillota, Bacteroidota, and Pseudomonadota were the dominant phyla of gut microbiota and served as the primary bacterial hosts of ARGs. Bacillota, as the main host phylum for aminoglycoside and MLS-class ARGs, showed increased abundance after CRS treatment, which was a key factor driving the significant enrichment of these two ARG classes. Furthermore, CRS increased the proportion of pathogenic bacteria such as vancomycin-resistant enterococci. Lactobacillus and Blautia were identified as potential hosts of tetP and ompR, respectively. The significant increases in the abundance of Lactobacillus and Blautia in the intestines of depressed rats after oral mirtazapine administration were critical factors for the marked enrichment of tetP and ompR. Conclusion CRS increases gut microbiota resistance risks by elevating the abundance of high-risk ARGs and pathogenic bacteria carrying ARGs. The effects of oral mirtazapine on the gut resistome are dependent on the initial microbiota composition. This study provides insights into the relationship between non-antibiotic drugs and gut microbiota resistance, offering important implications for the prevention and control of antibiotic resistance transmission.

Objective To investigate the effects of changes in single factors such as pH, metal ions, and NaCl concentration in the MG medium on the growth of Virgibacillus salexigens DSM 11483 and the yield of 5-hydroxyectoine (5-HE), optimize the culture conditions, and explore the mixed culture conditions of Halomonas campaniensis XH26 with V. salexigens DSM 11483 and the change in the yield of 5-HE. Methods We used a spectrophotometer was used to monitor the biomass (OD₆₀₀) of bacteria. The HPLC method was used to measure the yields of ectoine and 5-HE. The one-sample t-test was conducted to analyze the difference significance of the experimental data. Results The optimal culture conditions for V. salexigens DSM 11483 were as follows: pH 9.0, FeSO₄·7H₂O concentration of 1.00 mmol/L, and NaCl concentration of 2.0 mol/L. In this medium, the yields of ectoine and 5-HE were 200.4 mg/L and 80.0 mg/L, respectively. After “feeding” V. salexigens DSM 11483 with 40.0 mmol/L ectoine and culturing for 72 h, the yield of 5-HE reached 1 373.5 mg/L, which was 17.2 times that in the control group. After 72 h of mixed culture of H. campaniensis XH26 cultured for 24 h with V. salexigens DSM 11483 cultured for 36 h, the yields of ectoine and 5-HE were 1 535.1 mg/L and 168.7 mg/L, respectively, which were 7.7 times and 2.1 times the yield of V. salexigens DSM 11483 in pure culture. Conclusions The mixed culture of halophilic bacteria can make full use of their respective advantages to improve the synthesis and transformation efficiency of ectoine, demonstrating further research value.

Objective To investigate the mechanism by which the endophytic fungus Trichoderma harzianum Rifai help the seedlings of the rare medicinal plant Camphora migao (H. W. Li) Y. Yang, Bing Liu & Zhi Yang to defend against drought stress. Methods We simulated different drought stress gradients using the potted weighing method after inoculation of C. migao seedlings with T. harzianumvia rhizosphere injection and investigated the plant growth, physiological, and biochemical indexes. Results Under different drought conditions, inoculation with T. harzianum significantly increased the growth indexes such as biomass, plant height, and root growth of C. migao seedlings, compared with the uninoculated control group. Furthermore, T. harzianum significantly increased the activities of antioxidant enzymes and the content of osmotically regulation substances, reduced the malondialdehyde content, and elevated the content of photosynthetic pigments in the seedling leaves, which effectively mitigated the drought stress effects on the growth and development of C. migao seedlings. Conclusion T. harzianum improved the physiological responses of C. migao seedlings to drought stress by regulating osmotic balance and maintaining the stability of antioxidant system.

Objective To isolate lactic acid bacteria (LAB) with the ability to degrade milk fat, providing a theoretical foundation and technical support for dairy fermentation process optimization and probiotic development. Methods Primary screening employed media with butter as the main carbon source, followed by secondary screening using media with butter as the sole carbon source. The target strains were validated via carbon-free media. The selected strains underwent chromogenic assays for lipase characterization. Fermentation properties were assessed through viable count, acidity, acid value, and free fatty acid measurements. Probiotic potential was evaluated via acid/bile salt tolerance and cholesterol reduction assays. Results Through primary screening, secondary screening, and validation, ten strains with the ability to degrade milk fat were selected. Among them, a strain with faster growth than the others was identified as Lactobacillus delbrueckii grx601 through morphological and molecular biological characterization. This strain exhibited high lipase activity during logarithmic and stationary phases, with intracellular and extracellular enzyme activities of 14.14 U/mL and 11.45 U/mL, respectively. Enzymatic characterization showed that the optimal substrate for intracellular and extracellular lipases was p-nitrophenol palmitate, with the optimal reaction conditions of pH 7.0 and 40 ℃. The relative activity remained above 50% at 5% NaCl, which indicated certain salt tolerance. The fermentation characteristic experiment showed that L. delbrueckii grx601 significantly increased the acidity, acidity value, and free fatty acid content during the fermentation process. Moreover, the survival rates of L. delbrueckii grx601 in artificial simulated solutions with pH 3.0 and 0.30% bile salt were 83.87% and 47.70%, respectively, which indicated acid/bile salt tolerance of the strain. In addition, the cholesterol degradation rate of the strain was 7.95%. Conclusion L. delbrueckii grx601 was successfully isolated and characterized as a potent milk fat-degrading strain. Its high intra/extracellular lipase activity, favorable enzymatic properties, robust fermentation performance, and probiotic attributes (acid/bile salt tolerance, cholesterol reduction) indicate significant potential for dairy fermentation and probiotic applications.

Objective To isolate multifunctional phosphate-solubilizing bacteria (PSB) exhibiting psychrophilic adaptation and saline-alkaline tolerance in response to the ecological challenge of phosphorus limitation in saline-alkaline soils in cold regions, evaluate their phosphate-solubilizing efficiency and environmental adaptability, and preliminarily investigate their phosphate-solubilizing mechanisms. Methods We used an inorganic phosphorus-selective medium to isolate bacterial strains from saline-alkaline soils in Baicheng, Jilin Province. The phosphate-solubilizing capacity was quantitatively determined through the molybdenum-antimony colorimetric method. Taxonomic identification was performed through morphological characterization and phylogenetic analysis based on 16S rRNA gene sequences. The phosphate solubilization conditions were optimized via multi-parameter gradient optimization. HPLC was employed to quantify organic acid metabolites. Phenol-sulfuric acid assay and crystal violet staining were employed to characterize biofilm formation and extracellular polysaccharide (EPS) synthesis. Results The isolated strain Pseudomonas psychrophila MPP2402 demonstrated broad-spectrum environmental adaptability, maintaining stable growth at 5-30 ℃, pH 7.0-10.0, and 0.2-0.8 mol/L NaCl. The strain achieved 574.66 mg/L soluble phosphorus (14.8% increase) under optimal conditions: 15 ℃, pH 7.0, 0.4 mol/L NaCl, 1% inoculum density, and 5 g/L Ca₃(PO₄)₂. MPP2402 may exert the phosphate-solubilizing effect through the secretion of organic acids such as succinic acid (51.53 μg/mL), oxalic acid (22.84 μg/mL), tartaric acid (15.11 μg/mL), and malic acid (5.93 μg/mL), which worked in concert to solubilize phosphate. Additionally, the strain utilized EPS to construct a biofilm barrier and regulated the viable count in adverse environments such as low-temperature and saline-alkaline conditions. Conclusion The successful isolation of MPP2402 establishes a foundational resource for developing efficient saline-alkaline tolerant microbial agents and improving soil nutrient management in cold-region ecosystems.

Objective Saline-alkali soil is an important farmland resource in China. This study explored the effects of a bio-organic fertilizer fortified with a functional strain isolated from the crop rhizosphere of saline-alkali soil on the growth and the grain yield and quality of peanut plants in saline-alkali soil. The results are expected provide a solution for the development of specific microbial organic fertilizers for saline-alkali soil. Methods We first compared the rhizosphere bacterial communities of peanut plants growing in low-salt stress and non-salt stress soils, and identified the potential taxa improving the salt tolerance of plants that were enriched in the peanut rhizosphere under low-salt stress. A strain named HS6 capable of enhancing the salt tolerance of peanut plants was isolated from the rhizosphere soil of peanut plants. It was preliminarily identified as Bacillus paralicheniformis HS6. A microbial organic fertilizer was prepared by combining this strain with organic fertilizer. A field experiment was carried out in coastal saline-alkali land, including a control treatment (CK: decomposed organic fertilizer) and treatment 1 (T1: decomposed organic fertilizer supplemented with the cells of strain HS6). The growth and yield-related indicators of peanut plants were determined by counting and weighting, and the quality of peanuts was determined by the Kjeldahl method and the Soxhlet extraction method. Results The soil salt concentration higher than 0.3% significantly inhibited the growth of peanut plants. The principal component analysis revealed a significant difference in the peanut rhizosphere bacterial communities between low-salt stress (0.3%) and non-salt stress soils. Under low-salt stress, 22 differential taxa, mainly including Bacillaceae, were positively enriched in the peanut rhizosphere. The application of the organic fertilizer prepared with strain HS6 significantly promoted the growth, enhanced the biomass accumulation, and increased the number of nodules of peanut plants. The number of peanut nodules of T1 was 5 times that of CK. Moreover, the functional microbial fertilizer improved the yield and quality of peanuts. Compared with CK, T1 decreased the crude protein content of peanuts by 13.84%, while increasing the crude fat content of peanuts by 5.63%. Conclusion Low-salt stress can promote the enrichment of functional microbial taxa capable of enhancing salt tolerance in the peanut rhizosphere. The microbial organic fertilizer fortified with the functional strain enriched in the rhizosphere under salt stress can significantly improve the yield and quality of peanuts, demonstrating the potential to serve as a special microbial fertilizer for saline-alkali soil.

Porcine hemagglutinating encephalomyelitis virus (PHEV), a member of the betacoronavirus genus, is widespread in swine herds and the only known coronavirus causing neurological diseases in pigs. Objective To characterize the genomic features and phylogenetic relationship of a PHEV strain isolated from China. By investigating the biological properties of the virus, we assessed its epidemiological status and identified genetic variation patterns and evolutionary trends, providing a scientific basis for developing targeted prevention and control strategies. Methods RT-PCR detection was performed on suspected PHEV-positive samples collected from a large pig farm in Jiangsu Province, China, followed by virus isolation. The isolated virus was validated by indirect immunofluorescence assay (IFA), transmission electron microscopy (TEM), and whole genome sequencing. Phylogenetic analysis was performed based on the complete genome, S gene, HE gene, and NS2 gene. Results A PHEV strain, designated as PHEV JS-2025, was successfully isolated from the brain tissue sample. IFA showed strong red fluorescence signals in the cytoplasm, and TEM revealed typical coronavirus particles with a diameter of approximate 150 nm. The strain showed vigorous propagation in HRT-18 cells, reaching the peak viral titer at 72 h, with a 50% tissue culture infectious dose (TCID₅₀) of about 10^4.3 TCID₅₀/mL. PHEV JS-2025 could infect HRT-18, NPTR, and LLC-PK1 cells, and to a lesser extent, human intestinal Caco-2 cells. Whole genome sequencing revealed that the genome of PHEV JS-2025 was 30 044 bp in length, with over 94.9% nucleotide sequence identity to 14 reference PHEV strains, clustering within the rvPHEV-L-1 lineage. Of note, a mutation in the NS2 gene caused a premature termination at amino acid 19, resulting in the functional loss of the NS2 protein. Conclusion A novel PHEV strain JS-2025 from Jiangsu Province was successfully isolated and identified. This strain exhibits unique cellular tropism and can infect human intestinal cell lines, showing a risk of cross-species transmission. The truncated NS2 gene may affect the pathogenic mechanism of this strain. This study aids in understanding the genetic evolutionary characteristics and epidemiological features of PHEV and has implications for the prevention and control of PHE.

Nitrification inhibitors can affect the biological transformation process of ammonium nitrogen to nitrate nitrogen in soil by inhibiting the activity of ammonia-oxidizing bacteria (AOB). Objective To investigate the effects of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on the community structure and assembly mechanisms of AOB in coastal saline-alkaline paddy soil. Methods To study the effects of the typical nitrification inhibitor DMPP addition on the diversity, community structure, and community assembly process of AOB in soil under two salinity levels. Pot experiments and high-throughput sequencing were employed to determine the diversity, community structure, and community assembly process of AOB. Results The addition of DMPP increased the alpha diversity of AOB in soil, which reached a significant level in the high-salinity soil. The addition of DMPP significantly changed the community composition of AOB, reducing the relative abundance of taxa with high relative abundance and enriching the taxa with low relative abundance. The decrease in relative abundance of taxa with high relative abundance was the main reason for the inhibition of DMPP on nitrification. Principal coordinates analysis revealed that the community structure of AOB changed significantly after the addition of DMPP, which was more obvious in high-salinity soil. The null model analysis results showed that stochastic processes played a dominant role in the community assembly process of AOB, and the contribution of stochastic processes increased after the addition of DMPP. Canonical correspondence analysis and Mantel’s test indicated that soil pH, electrical conductivity, organic matter, total nitrogen, and alkaline-hydrolyzable nitrogen were the main physicochemical factors influencing changes in AOB community structure. Conclusion DMPP exerted significant impacts on AOB communities in coastal saline-alkaline paddy soils across varying salinity levels, with its inhibitory effects varying substantially with soil salinity.

Objective We compared the rhizosphere microbial interaction network structure and keystone taxon identification arising from distinct network construction algorithms, aiming to clarify the characteristics and advantages of each algorithm in inferring microbial interactions and identifying keystone taxa, thereby providing a theoretical basis for methodological selection. Methods Taking the rhizosphere microbial community of Camphora migao (a rare plant) as the model system, we constructed molecular ecological networks with three mainstream algorithms: sparse correlations for compositional data (SparCC), random matrix theory (RMT), and co-occurrence network (CoNet). We comprehensively compared network structural features and keystone taxon identification across algorithms by integrating PICRUSt2 functional prediction with keystone taxa-environmental factor correlation analysis. Results Network construction algorithms significantly influenced the topological properties of networks. SparCC generated highly modular networks (relative modularity index, RM=1.31) with distinct interaction segregation (edge connectivity=0). RMT produced a single-module structure (RM=0.78) and homogeneous connectivity (closeness centralization index=0.22). Integration of 26.0% negative correlations in CoNet reduced modularity (RM=0.95), increased network diameter (33.22 steps), and decreased robustness. Keystone taxon identification was method-dependent. Specifically, CoNet, SparCC, and RMT identified 224.00, 44.00, and 19.00 keystone taxa, respectively, with<9.2% cross-method overlap. Rhizobiales and Acidobacteriales were consistently identified as core keystone taxa by all methods, demonstrating cross-algorithm stability. The correlation analysis with environmental factors confirmed that these shared taxa significantly correlated with β-glucosidase activity, validating their role in cellulose degradation and highlighting methodological consistency in identifying key ecological processes. Conclusion The three algorithms exhibited complementary strengths: CoNet resolved complex competitive interactions; SparCC reliably assessed functional stability; RMT uncovered core functional modules. The correlation analysis with environmental factors validated the cellulose degradation function of keystone taxa, with high cross-method consistency in core ecological process identification. Our work provides a theoretical foundation for elucidating plant-microbe interactions and optimizing microbial network construction.

The cyclic oligonucleotide (CO)-based anti-phage signaling system (CBASS), an innate immune system widely distributed in bacteria, is composed of oligonucleotide cyclases cGAS/DncV-like nucleotidyltransferases (CD-NTases), CD-NTase-associated protein (Cap), and accessory proteins. When bacteria are infected by phages, CD-NTases generate COs to amplify signals. Subsequently, effectors are activated by COs, inducing cell death through multiple mechanisms such as damaging cell membranes, degrading DNA, and depleting essential metabolites. Accessory proteins are responsible for regulating the CBASS, ultimately inhibiting phage infection. This review introduces the composition and classification of CBASS and further discusses the process by which CD-NTases recognize and bind to phage RNA to activate the synthesis of the second messenger CO. Effectors encoded by Cap effector genes mediate cell killing by binding to COs, while accessory proteins encoded by Cap auxiliary genes are involved in regulating the activity of CBASS. In addition, the immune evasion of phages from CBASS is also discussed. This review helps to understand the detailed mechanisms and biological significance of the interactions between phages and their host bacteria from the perspective of CBASS.