Objective To establish a mouse model that effectively simulates the key clinical features of porcine Senecavirus A (SVA) infection, providing a crucial experimental tool for elucidating its pathogenesis and evaluating prevention and control products. Methods Five-week-old SPF C57BL/6J wild-type (WT) mice and type I interferon receptor-deficient (C57BL/6J ^IFNR-/- ) mice were inoculated via intraperitoneal, subcutaneous, and intramuscular routes. Blood and tissue samples were collected on days 1, 3, and 5 post-infection (dpi) for analysis of gross pathology, histopathology, viral load, and dynamic determination of inflammatory cytokines at the mRNA level. Results Compared with the mock-infected control group, both mouse strains developed gross lesions (e.g., swollen inguinal lymph nodes, yellowish livers, splenomegaly) and histopathological lesions (e.g., cortical disintegration of lymph nodes, hepatocellular necrosis, atrophy of splenic white pulp, and renal tubular necrosis). However, these lesions were more severe in C57BL/6J ^IFNR-/- mice. Viral RNA was widely distributed in tissues of both groups but was significantly higher in the C57BL/6J ^IFNR-/- group. Notably, viremia was undetectable in WT mice, whereas in C57BL/6J ^IFNR-/- mice, the virus was detected in whole blood as early as 1 dpi, peaked at 3 dpi, and then declined rapidly. Inflammatory cytokine analysis revealed significantly higher mRNA levels and protein levels of IL-1β and IL-6 in C57BL/6J ^IFNR-/- mice than in WT mice. Conclusion The C57BL/6J ^IFNR-/- mouse model successfully simulates, for the first time, the transient viremia characteristic of porcine SVA infection. It comprehensively replicates key features, including the multi-organ viral distribution, high viral load, and self-limiting recovery, providing a more effective animal model for delving into the pathogenic mechanism of SVA and evaluating vaccines and antiviral drugs.

Objective The effects of the helper strain (Priestia endophytica)1-112 on the growth of Ketogulonicigenium vulgare and the biotransformation of 2-keto-L-glonic acid (2-KLG) remain unclear. In this study, we cultured the helper strain in different media to study the mechanisms of the growth- and 2-KLG biotransformation-promoting effects of the helper strain on K. vulgare. Methods We used different media (minimal, mixed, and fementation media) to culture the helper strain and investigated the effects of the strain on the growth and 2-KLG biotransformation of K. vulgare. The differently expressed genes (DEGs) and associated metabolic pathways in the helper strain cultured in different media were analyzed by transcriptomics to screen the key factors in the co-culture system. The effects of key factors on the growth and 2-KLG biotransformation of K. vulgare were evaluated to explore their roles in the co-culture system. Results Strain 1-112 cultured in the minimal medium lost or reduced the ability to promote 2-KLG production, while it retained the ability to promote the growth of K. vulgare. This result indicated that the helper strain promoted 2-KLG biotransformation through two distinct mechanisms. There were 1 859 DEGs in strain 1-112 cultured in fermentation medium in comparison with the minimal medium, and the DEGs were significantly enriched in the pathways such as nicotinate and nicotinamide metabolism, carbon metabolism, arginine and proline metabolism, and amino acid biosynthesis. In addition, the helper strain cultured in the minimal medium containing some key factors could restore the ability to promote 2-KLG production. Glycine, proline, biotin, and nicotinic acid were found to be essential for promoting K. vulgare growth, whereas glycine, threonine, biotin, and nicotinic acid played critical roles in enhancing 2-KLG biotransformation. Conclusion The helper strain promoted the growth and 2-KLG biotransformation of K. vulgare through different mechanisms.

Objective In view of the production and environmental issues caused by excessively high nicotine content in upper tobacco leaves, this study aims to decipher the molecular mechanism of nicotine degradation by an efficient nicotine-degrading strain Pu17 screened out in the previous study via genomic approaches. Methods The taxonomic status of the strain was determined by average nucleotide identity (ANI) analysis. Whole genome sequencing and annotation were employed to clarify the nicotine metabolic pathway. Key intermediates during degradation were detected by MS/MS. Live plant trials were conducted to explore the optimal application method for nicotine reduction. Results Phylogenetic analysis revealed an ANI value of 96.51% between Pu17 and Peanarthrobacter ureafaciens, identifying Pu17 as a strain of P. ureafaciens. The genome of Pu17 was 4.47 Mb in length, with the G+C content of 63.34%, encoding 4 155 proteins. Functional annotation and comparative genomics identified unique gene clusters related to heavy metal resistance, cell surface synthesis, and metabolic potential in Pu17, which constituted its environmental adaptation strategy. Metabolite analysis detected key intermediates such as 6-hydroxypseudooxynicotine. This result, combined with that of genomic analysis, confirmed that Pu17 degraded nicotine via the pyridine pathway, with key genes (e.g., nboR, mao, and 6-hlno) primarily located on plasmids. Efficacy evaluation demonstrated that the Pu17 fermentation broth effectively reduced nicotine content in tobacco plants through both foliar spraying and root irrigation, achieving a maximum degradation rate of 14.00% in live leaves. Conclusion This study systematically elucidates the molecular mechanism and application potential of P. ureafaciens Pu17 for nicotine degradation from genomic, metabolomic, and application perspectives. It provides a theoretical basis and microbial resources for the development of bioremediation technologies for tobacco waste and harm reduction.

Objective To construct a recombinant Escherichia coli strain for the expression of the bacteriophage-derived lytic enzyme Lys162, an efficient and broad-spectrum recombinant enzyme, thus providing a technological foundation for developing novel antimicrobial agents. Methods On the basis of the whole-genome sequencing data of bacteriophage pEC.M2929.1AR.1, the protein structure was predicted via bioinformatics tools, and molecular docking analysis was performed to evaluate the substrate-binding affinity. The expression vector pET28a(+)-Lys162 and the engineered E. coli BL21(DE3) expression system were constructed. Lys162 was further assessed for its environmental stability, in vitro antibacterial activity, and lytic spectrum. Results Structural analysis predicted that Lys162 was an N-acetylmuramidase-type lytic enzyme containing a conserved catalytic domain. Molecular docking confirmed its high-affinity binding to peptidoglycan. The enzyme was expressed in a soluble form in E. coli BL21(DE3) and purified to reach a concentration of 1.89 mg/mL. In vitro assays demonstrated that Lys162 at 125 μg/mL exhibited significant lytic activity against E. coli M2929.1AR, along with potent lytic effects against multiple pathogenic bacteria including Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter spp. The enzyme retained stable activity within a pH range of 4.0-11.0 and at temperatures between 4 ℃ and 60 ℃. Conclusion Lys162 transcends the host specificity of its parental phage, demonstrating broad-spectrum antimicrobial activity and considerable environmental adaptability. Its synergistic effect with EDTA suggests a practical strategy for performance optimization. These results establish a foundation for developing novel enzymatic antimicrobials to address challenges associated with bacterial antibiotic resistance.

Objective Transient receptor potential vanilloid 4 (TRPV4), a non-selective cation channel, is deeply involved in the physiological and pathological regulation of multiple organ systems, while the comprehensive influencing mechanism of its mutation on animal intestines and intestinal flora is not clear. This study explored the regulatory effects of Trpv4 exon 8 c.1491+1G>A mutation on intestinal barrier integrity and flora-metabolic microenvironment in mice, aiming to provide an experimental basis for analyzing the interaction mechanisms between host genes and intestinal flora. Methods Trpv4 exon 8 c.1491+1G>A gene-edited mice previously constructed in our laboratory were taken as the research objects, and the expression levels of Trpv4 and TRPV4 in the intestinal tissue were determined by qPCR and Western blotting, respectively. Pathological sections were prepared for observation of the structural changes of the intestinal tissue. The 16S rRNA gene high-throughput sequencing was conducted to reveal the structural differences of intestinal flora. Non-targeted metabolomics based on LC-MS was employed to examine the changes of fecal metabolites, and the correlations between flora and metabolites were analyzed. Results Trpv4 editing led to the abnormal expression of Trpv4 and TRPV4 in the intestinal tissue of mice, which resulted in the structural abnormality of the intestinal tissue and the impairment of intestinal barrier function. In addition, the gene-edited mice exhibited an imbalance in intestinal flora, with significantly increased relative abundance of Bacteroidota, a significantly decreased Bacillota/Bacteroidota (F/B) ratio, and reduced abundance of common commensal bacteria such as Staphylococcus. Metabolomic analysis indicated that the gene-edited mice presented disordered lipid metabolism and abnormalities in immune-related metabolites. The abundance of Bacteroidota was positively correlated with lipid metabolites, while that of Desulfovibrio and Enterobacter was negatively correlated with lipid and immune metabolites. Conclusion Trpv4 exon 8 c.1491+1G>A gene-edited mice exhibited impaired intestinal barrier function, along with alterations in intestinal flora structure and the metabolic microenvironment. This study provides basic data for elucidating the interactions between specific gene mutations and the gut microbiota and offers theoretical support for the development of diagnostic and therapeutic strategies for Trpv4-related diseases.

Listeria monocytogenes, as a major causative agent of foodborne illness outbreaks, poses a serious threat to food safety and public health. In complex foodborne pathogen environments, the specific and effective detection methods for L. monocytogenes are crucial. Objective To develop a novel recombinase-aided amplification-exonuclease (RAA-exo) assay for detecting L. monocytogenes. Methods Multiple RAA primer and probe sets targeting hly were designed, and the optimal primer set was selected based on nucleic acid amplification efficiency. The reaction system was rigorously optimized, focusing on the concentrations of A buffer, B buffer, and RAA primers and probe. Results The optimized RAA-exo assay showed a limit of detection (LOD) of 0.5 copies/μL for recombinant plasmids and 10 CFU/mL for L. monocytogenes suspensions. The assay demonstrated high specificity, selectively detecting L. monocytogenes without cross-reactivity to other common foodborne pathogens, including Salmonella, Escherichia coli, Staphylococcus aureus, Bacillus cereus, or other Listeria species (L. ovinae, L. seeligeri, and L. innocua). In a validation study using 44 pork samples, the RAA-exo assay results were in complete agreement with those of the real-time fluorescence PCR internal standard method outlined in the industry standard SN/T 5224—2019. Conclusion The developed RAA-exo assay exhibits high sensitivity and specificity, requires minimal hands-on time, and achieves detection within 20 min at 37 °C. Therefore, the assay is suitable for rapid, on-site testing, serving as an efficient and convenient tool for L. monocytogenes detection, with promising applications in food safety monitoring.

Objective To prepare reference material (RM) for positive serum specific for genotype Ⅱ African swine fever virus (ASFV) for serological detection, quality control, and proficiency testing (PT). Methods The anti-serum collected from specific pathogen-free (SPF) swine immunized with inactivated genotype Ⅱ ASFV was used as raw material for the preparation of RM. Indirect enzyme-linked immunosorbent assay (iELISA) was employed to evaluate the purity, specificity, homogeneity, and stability of RM. In addition, RM was characterized by nine laboratories and applied in clinical trials by three laboratories. Results A total of five hundred bottles of RM for positive serum specific for genotype Ⅱ ASFV strain HLJ/18 were successfully prepared. The results indicated that the RM we prepared was pure, homogenous, and free of exogenous virus contamination, showing good specificity, homogeneity, and stability. The RM was stable for at least 18 months when it was stored at -20 ℃ and for at least 7 days at 4 ℃, 25 ℃, and 37 ℃. The characterization by the nine laboratories showed that the RM was positive for antibodies against genotype Ⅱ ASFV. Conclusion The positive serum specific for genotype Ⅱ ASFV strain HLJ/18 has successfully been prepared, providing critical material for ASF detection and diagnosis.

Nitrogen deposition is a major driver shaping the structures and functions of forest ecosystems worldwide. When nitrogen inputs exceed ecosystem critical loads (CLs), significant changes in the diversity and abundance of understory herbaceous plants can occur. This study aims to systematically compile and integrate critical load data for understory herbaceous plants in response to nitrogen deposition across three mycorrhizal types: arbuscular mycorrhiza (AM), ectomycorrhiza (ECM), and mixed arbuscular-ectomycorrhizal forests (AM+ECM), in forests. By establishing a dedicated and standardized database, this work facilitates comparisons of herbaceous plant responses to nitrogen inputs among different mycorrhizal types in forests and provides a scientific basis for assessing the impacts of nitrogen deposition on forest microbe-plant systems. On the basis of the published literature and the global nitrogen deposition critical load database developed by Wilkins et al., relevant data were systematically collected, screened, and standardized to construct the Database of Critical Loads of Nitrogen Deposition for Understory Herbaceous Plants across Different Mycorrhizal Types in Forests. All critical load values were consistently derived via the threshold indicator taxa analysis (TITAN) method. A rigorous quality control workflow was applied, including cross-validation of mycorrhizal types, outlier detection and treatment, and data standardization. The database contains 3 592 standardized records. The core data table includes the following fields: Latin name of herbaceous plant species, forest alliance, mycorrhizal types (AM, ECM, or AM+ECM), species-level critical load values (zenv.cp) estimated by TITAN with corresponding bootstrap uncertainty intervals (5th, 10th, 50th, 90th, and 95th percentiles), response direction (increase or decrease in abundance), purity and reliability metrics, community-level change points (CCP), and associated environmental metadata. The database covers the three major mycorrhizal types as well as graminoid and non-graminoid herbaceous functional groups in forests. This database represents the first large-scale, standardized database explicitly focusing on the relationships among mycorrhizal types, understory herbaceous plants, and nitrogen deposition critical loads in forests. Its standardized structure, transparent metadata, and stringent quality control procedures ensure its reliability for future research and applications, including nitrogen deposition risk assessment, comparative analyses of mycorrhizal functions, ecological model parameterization, and the formulation of biodiversity conservation strategies.

Engineered microorganisms, as the core driving force of biomanufacturing and the development of the new bio-economy, demonstrate increasingly prominent strategic values. The newly built Engineered Microorganisms and Genetic Tools Collection Center of China (EMTCC) supported by the Ministry of Education aims to break through the limitations of “microbial culture collection centers” and provide a comprehensive resource innovation service platform supported by information technology and integrating resource acquisition, intelligent creation, data analysis, and open sharing functions. This platform intends to meet the needs of basic research, technology development, and industrial applications. This article elaborates on the building framework of EMTCC, which takes large-scale resource preservation as the basis, intelligent mining and analysis as the core, and digital storage and computing sharing as the link. By carrying out large-scale acquisition and standardized preservation of natural and engineered microorganisms and plasmids and integrating cutting-edge technologies such as high-throughput automation, multi-omics, single-cell analysis, artificial intelligence prediction models, and digital twins, the EMTCC achieves a complete process of “acquisition & preservation, analysis & identification, and data sharing”. On the basis of drawing on the standardization and quality control systems of internationally renowned institutions such as American Type Culture Collection (ATCC), a resource repository model integrating living “organisms, information, and intelligence” will be developed. This innovative practice is expected to provide strong resource guarantee and technical support for research innovation and industrial upgrading in the fields of synthetic biology, metabolic engineering, biomedicine, and environmental remediation.