6′-sialyllactose (6′-SL) is an important component of porcine breast milk oligosaccharides, and sialic acid (SIA) is the monomer of sialylated breast milk oligosaccharides. Both can regulate the structure of human colonic microbiota. However, there are few reports regarding the effects of SIA and 6′-SL on the composition and fermentation characteristics of piglet colonic microbiota in vitro. [Objective] To investigate the effects of SIA and 6′-SL on the composition and fermentation characteristics of colonic microbiota in suckling piglets, aiming to provide a reference for using these substances to regulate gut health in piglets. [Methods] We used mixed colonic chyme from three suckling piglets as the microbial inoculum. The experiment was conducted with four groups: no carbon (NCB), lactose (LAC), SIA, and 6′-SL, each with four replicates. [Results] After 24 h of fermentation, the pH in the 6′-SL group was higher than that in the LAC group (P<0.05). After fermentation for 12 h and 24 h, the gas production in the SIA and 6′-SL groups was lower than that in the LAC group (P<0.05). At the time point of 24 h, the SIA and 6′-SL groups had higher acetic acid content and lower propionic acid and butyric acid content than the LAC group (P<0.05). Moreover, the SIA and 6′-SL groups had higher Chao1 and ACE indices than the LAC group (P<0.05). Beta diversity of the microbial community in the LAC, SIA, and 6′-SL groups changed (P<0.05). As fermentation progressed, compared with LAC, SIA increased the relative abundance of Bacillota, Anaerovibrio, and Faecalibacterium and decreased that of Pseudomonadota, Escherichia-Shigella, Mitsuokella, and Streptococcus (P<0.05); 6′-SL increased the relative abundance of Bacteroidetes, Prevotella, Bacteroides, and Roseburia and decreased that of Pseudomonadota, Bacillota, Megamonas, Escherichia-Shigella, Mitsuokella, and Prevotellaceae_NK3B31_group (P<0.05). [Conclusion] Both 6′-SL and SIA can effectively regulate the gut microbiota structure in piglets. Specifically, 6′-SL increases the relative abundance of Bacteroidetes, Prevotella, and Bacteroides, while SIA increases that of Bacillota and Anaerovibrio. Both substances promote colonic microbial fermentation in piglets to increase the production of short-chain fatty acids (SCFAs), especially acetic acid.

[Objective] To establish a triple qPCR detection method for Mycoplasma bovis, Pasteurella multocida (P.m) and Mannheimia haemolytica (M.h), and to conduct an epidemiological investigation of bovine respiratory disease complex (BRDC) in large-scale dairy farms with it. [Methods] Sensitive quality control samples were prepared using the purified strains isolated and identified in our laboratory. The conserved genes of the major prevalent strains in China were used as targets, including the uvrC of M. bovis, Kmt1 of P.m, and lktD of M.h, to establish a multiplex qPCR containing multiple pairs of primers and probes. By optimizing the parameters of the reaction system, a triple qPCR method was established and its sensitivity, repeatability and specificity were verified. The coincidence rate with the bacterial isolation and identification method was verified. A total of 1 252 clinical samples suspected of BRDC were tested using the established method, and the prevalence and spatiotemporal distribution characteristics of three pathogens were analyzed based on the test results. [Results] The R² values of the standard curves for the triple qPCR for detecting M. bovis, P.m, and M.h were 0.998 6, 0.994 6 and 0.998 6 respectively; the minimum detectable quantities were 2.50×10³, 1.26×10³ and 7.50×10² CFU/mL, respectively. The intra-batch and inter-batch coefficients of variation of the reaction system were both less than 2%, and only the specific amplification curves were observed for the three sensitive quality control samples established. The results of the test showed that the concordance rates of M. bovis, P.m, and M.h with bacterial isolation and identification methods were 100.00%, 98.40% and 97.60%, respectively. The epidemiological survey indicated that the total positive rate of bacterial pathogens in BRDC was 75.9% (95% confidence interval (CI), 73.4%-78.3%), among which the proportion of mixed infections was 48.8%. The incidence was higher in winter, and the positive rate in the northern region was significantly higher than that in the southern region (P<0.001). [Conclusion] The multiple qPCR method established in this study demonstrated excellent specificity, stability and repeatability, which provided a candidate solution for the detection of major pathogens of BRDC in China. The analysis of the co-infection characteristics and geographical-seasonal distribution patterns of BRDC bacterial pathogens offered meaningful references for the formulation of precise prevention and control strategies.

[Objective] To explore the protective effect of selenomethionine (Se-Met) on oxidative stress and intestinal barrier damage in mice infected with porcine deltacoronavirus (PDCoV) and the potential regulatory mechanism. [Methods] Forty female C57 mice were randomly grouped as follows: control, Se-Met (0.3 mg/kg Se), PDCoV, and Se-Met+PDCoV (0.3 mg/kg Se). After being fed with or without Se-Met for 23 days, the mice in the PDCoV group and the Se-Met+PDCoV group were administrated with 300 μL suspension of PDCoV HNZK-02-P5 strain (1×10⁶ TCID₅₀) by gavage, while those in the other two groups were administered with the same volume of Dulbecco’s Modified Eagle Medium (DMEM). All the mice were observed daily for clinical signs, food intake, and body weight changes until day 28. At five days post-inoculation (dpi), intestinal tissues were collected and PDCoV titers were determined. Hematoxylin staining and eosin staining were used to monitor pathological changes in intestinal tissues. Oxidative stress-related indicators such as malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GSH-PX) were investigated. The level of ROS in the jejunum tissue was measured via a 2′,7′-dichlorofluorescein diacetate (DCFH-DA) probe. Immunofluorescence was used to analyze the changes of small intestinal tight junction proteins (ZO-1 and Occludin). The mRNA levels of inflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-10), intestinal tight junction proteins (ZO-1 and Occludin), and the Nrf2 signaling pathway-associated factors (Nrf2, HO-1, and NQO1) were determined by RT-qPCR. Western blotting was employed to assess the protein levels of factors related to the Nrf2 signaling pathway. [Results] The results of body weight, food intake, pathological examination, and viral RNA titers in different intestinal tissues revealed that Se-Met might increase the body weight, decrease viral titers in intestinal tissues, and attenuate PDCoV-induced structural damage of intestinal villi in PDCoV-infected mice. Se-Met attenuated PDCoV-induced inflammation by lowering the mRNA levels of major inflammatory cytokines, such as IL-1β, IL-6, and TNFα in the jejunum. Se-Met ameliorated PDCoV-induced intestinal mucosal barrier damage by up-regulating the mRNA levels of ZO-1 and Occludin in the jejunum. Se-Met ameliorated PDCoV-induced oxidative stress by decreasing the levels of ROS and MDA and increasing the levels of GSH-PX and SOD in the jejunum. Se-Met inhibited PDCoV-induced oxidative stress by activating the Nrf2 signaling pathway. [Conclusion] Se-Met may attenuate the intestinal injury in mice infected with PDCoV by activating the Nrf2 signaling pathway, which provides a theoretical basis for the prevention and treatment of PDCoV infection.

[Objective] This study investigates the effects of various diets on the structure and diversity of the fungal community in the tobacco beetle Lasioderma serricorne, aiming to provide a theoretical basis for developing green control strategies for stored-product pests through microbial regulation. [Methods] The PacBio SMRT platform was used for full-length internal transcribed spacer (ITS) amplicon sequencing, on the basis of which the community structure characteristics of fungi in L. serricorne were compared among three groups: artificial feed (SL), tobacco domestication (YC), and wild environment (WF). Additionally, culturable fungi were isolated via the culture method, and the tissue expression pattern of the core symbiotic fungus Symbiotaphrina kochii was localized by RT-qPCR. [Results] SL, YC, and WF groups contained 35, 32, and 15 operational taxonomic units (OTUs), respectively. The core OTUs shared by the three groups accounted for 31.43%, 34.38%, and 73.33% in SL, YC, and WF groups, respectively. The Sobs index of the SL group was 29.00±1.13, which was higher than those of the YC group (16.17±2.30) and WF group (12.33±1.33) (P<0.001). Symbiotaphrina was the core functional group shared by the three groups, and its relative abundance was more than 81.000 0% in all the three groups. Aspergillus and Xeromyces were the characteristic genera of the SL and YC groups, while Symbiotaphrinabuchneri and Symbiotaphrina microtheca formed the evolutionary clades specific to the YC and WF groups. Eight Ascomycota strains were isolated via the culture method, belonging to three genus: Symbiotaphrina (three strains), Talaromyces (three strains), and Penicillium (two strains). Tissue-specific expression analysis confirmed the higher expression level of S. kochii in mycetocytes (10.42±1.03) than in the fat body (0.74±0.08) and midgut (0.31±0.01) (P<0.001), validating its intracellular colonization. [Conclusion] This study for the first time reveals that diets regulate the fungal community assembly in L. serricorne through a “nutrient-microbiota” interaction network and demonstrates the pivotal role of Symbiotaphrina in adaptive evolution of the host. These findings establish a theoretical foundation and provide critical targets for developing precision pest control technologies based on targeted modulation of microbial interaction networks.

[Objective] To investigate the role of Listeria monocytogenes LPXTG motif-anchored protein Lmo0130 in infection causing diseases, the bacterial growth, infection in cell and host among the L. monocytogenes wild-type, lmo0130-deleted and lmo0130-complementary strains were compared. [Methods] The lmo0130-deleted strain Δlmo0130 and lmo0130-complementary strain CΔlmo0130 were constructed to investigate the effects of Lmo0130 on the abilities of bacterial growth, cell surface adhesion and invasion, intracellular proliferation, intercellular migration, survival of infected mice, and bacterial load in mouse organs, ultimately demonstrated the role of L. monocytogenes Lmo0130 in cell and host infection. [Results] LPXTG motif-anchored protein Lmo0130 contributed to cell surface adhesion and invasion, intracellular proliferation, specific colonization in the liver and spleen, and pathogenicity in mice. However, it had no effect on bacterial growth or intercellular migration. [Conclusion] Lmo0130 contributes to cell and host infection of L. monocytogenes finally.

DNA methylation is an important way of epigenetic regulation in bacteria. Alphaproteobacteria methylate DNA by using the cell cycle-regulated DNA methyltransferase (CcrM). CcrM does not contain a functional unit of restriction endonuclease, thus belonging to an orphan methyltransferase. By methylating adenine in DNA sequences, CcrM influences the interaction between DNA and proteins, regulates the expression of numerous genes, and is crucial for the regulation of processes such as the cell cycle of Alphaproteobacteria. We reviewed the function, structure, and epigenetic regulation of CcrM, clarified the mechanisms of CcrM in DNA recognition, catalysis, and activity regulation, summarized the mechanism by which the global cell-cycle regulator (GcrA) utilizes the methylation signals produced by CcrM to regulate gene expression, and provided an outlook on the potential future research directions of CcrM, providing a reference for further in-depth study of the epigenetic regulation mechanisms in bacteria.

Saline-alkali soil is extensively distributed in the Songnen Plain of Northeast China, posing a major constraint on the grain yield. It has been demonstrated that endophytic bacteria of plants could promote plant growth and enhance plant tolerance to environmental stress. Agastache rugosa had been experimentally verified to exhibit strong salt tolerance. [Objective] To isolate and screen salt-alkali-tolerant endophytic bacteria from A. rugosa grown under high-salinity conditions and explore microbial resources for promoting plant growth under stress. [Methods] A. rugosa seedlings surviving under 200 mmol/L NaCl were selected to isolate endophytic bacteria by the tissue culture method. Salt-alkali tolerance of the endophytic bacteria was assessed by plate assays, and the plant growth-promoting and antimicrobial properties were also evaluated. [Results] A total of 95 endophytic bacterial strains were isolated from the leaves, stems, and roots of A. rugosa seedlings, of which 20 strains tolerated 15% NaCl and 14 strains could grow at pH 10.0. The selected elite salt-tolerant strains possessed plant growth-promoting properties such as indole-3-acetic acid (IAA) synthesis, siderophore production, and nitrogen fixation. Additionally, 18 strains showed resistance against three plant pathogens. The principal component analysis on plant growth-promoting properties, salt tolerance, and antimicrobial properties screened out strains YL-14, YS-35, and YR-18, which were molecularly identified as Bacillus sp. Under different salt stress conditions, three bacterial strains demonstrated significant growth-promoting effects on A. rugosa seedlings. Specifically, under 100 mmol/L salt stress, YL-14, YS-35, and YR-18 increased the seed germination rate by 5.5%, 8.5%, and 7.0% and the fresh root weight by 34.9%, 124.0%, and 127.0%, respectively. Strains YS-35 and YR-18 increased the main root length by 40.9% and 49.5%, respectively. [Conclusion] Endophytic bacterial strains YL-14, YS-35, and YR-18 with strong saline-alkali tolerance and plant growth-promoting properties were isolated from A. rugosa. These strains show great potential for development as bioinoculants and application in other crops to enhance crop stress resistance and growth, serving as new microbial resources for the utilization of saline-alkali soil.

The gut microbiota plays a pivotal role in regulating animal health, and its structure and function can be significantly modulated by fermented feed. However, the lack of cross-species comparative studies has hindered a comprehensive understanding of the universal mechanisms underlying fermented feed-mediated microbial regulation. [Objective] To integrate multi-species data for deciphering cross-species regulatory patterns of fermented feed on gut microbiota and elucidating universal functional optimization and host-specific mechanisms. [Methods] We aggregated 464 gut microbiome datasets from pigs, cattle, chickens, and geese. The alpha/beta diversity analyses, linear discriminant analysis effect size (LEfSe), BugBase, and network analyses were employed to assess the diversity, differentially enriched genera, pathogenicity, and interactions of the gut microbiota. [Results] Fermented feed markedly reduced the alpha diversity of gut microbiota in monogastric animals (pigs, chickens, and geese) but not in ruminants (cattle). Although the beta diversity of gut microbiota remained statistically stable in different animals, fermented feed enriched probiotics (e.g., Lactobacillus and Faecalibacterium) while suppressing pathogens (e.g., Campylobacter and Brachyspira) to significantly diminish the pathogenic potential. Network analysis revealed enhanced connectivity, increased network density, reduced modularity, and improved community synergy in fermented feed groups. Host-specific responses were identified: Lactobacillus dominated in pigs, Akkermansia in cattle, and Flavonifractor in chickens. [Conclusion] Fermented feed modulates gut microbiota through a pattern coupling consistent response optimization with host-specific responses, selectively enriching keystone taxa to improve the specific function and reduce the pathogenicity. This study provides theoretical foundations for developing host-tailored fermented feed strategies.

Streptomyces is a genus of diverse actinomycetes known for producing antibiotics, showcasing high value for research and development. However, the limited number of Streptomyces species included in commercial databases restricts the application of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) in the identification of Streptomyces. [Objective] To establish a MALDI-TOF MS database for the identification of Streptomyces based on the mining of whole genome sequencing data and test its accuracy. [Methods] By searching against a genome database, we selected all the genome-sequenced type strains of Streptomyces. Subsequently, the sequences of 12 ribosomal proteins were extracted from their genome sequences and theoretical MALDI mass/charge (m/z) values were calculated. Accordingly, a database was established based on the combination of 12 theoretically calculated m/z values, which can be used as the identification criteria for Streptomyces species. Finally, type strains were randomly collected for MALDI-TOF MS testing. To test the accuracy of the database construction method and comparison results, we matched the experimental m/z values with the theoretically calculated m/z values of the species in the database. [Results] We established a MALDI-TOF MS database including 615 Streptomyces species. The mass spectra of the tested strains were accurately matched with those of corresponding species in the database. In addition, we proposed a method for the identification of Streptomyces by database comparison. [Conclusion] The database established in this study laid a foundation for identifying Streptomyces based on MALDI-TOF MS.

[Objective] Microorganisms play a critical role in the treatment of food waste. Elucidating their community structure and functional characteristics is essential for optimizing treatment processes and improving operational efficiency. [Methods] We employed high-throughput 16S rRNA gene amplicon sequencing to investigate the microbial community structures and potential functions in three systems: the anaerobic digestion system, the wastewater treatment system, and the air purification system (including biofilters and deodorization towers), in a food waste treatment facility. [Results] The microbial communities differed significantly in diversity and composition across systems. The anaerobic digestion system exhibited lower microbial diversity and richness, primarily influenced by environmental factors such as temperature, pH, and biochemical oxygen demand (BOD). Functional analysis indicated that organic matter degradation was the dominant microbial function across the facility. Specifically, the anaerobic system was enriched with genera such as Defluviitoga, Methanothermobacter, and Lentimicrobium, which were involved in hydrolysis, fermentation, and methanogenesis. The wastewater treatment system was dominated by Candidatus Anammoximicrobium, Nitrolancea, and Truepera, which drove organic matter degradation and nitrogen transformation processes, including anaerobic ammonium oxidation (anammox), nitrification, and denitrification. The air purification system was enriched with Chryseobacterium and Paracoccus, which were associated with biofilm formation and the degradation of volatile organic compounds and sulfur-containing compounds. [Conclusion] The microbial community characteristics in each treatment system was closely associated with system-specific operational conditions. The enrichment of functionally distinct microbial taxa reflected their ecological roles. In the anaerobic digestion system, methanogens and syntrophic bacteria cooperatively facilitated organic matter degradation and methane production. In the wastewater treatment system, nitrogen-cycling bacteria ensured efficient nitrogen removal. In the air purification system, the enrichment of heterotrophic degraders and sulfur compound-metabolizing genera (e.g., Sphingobium and Flavobacterium) enhanced deodorization performance. These findings provide a theoretical basis for microbial community regulation and process optimization in food waste treatment facilities.