Legionnaires’ disease, a serious pulmonary infection caused by Legionella, requires early diagnosis for effective treatment and favorable outcomes. Laboratory diagnostic methods primarily encompass isolation and culture, antigen detection, nucleic acid detection, and serological testing. Although isolation and culture are considered the gold standard, it is characterized by low sensitivity and extended culture duration. Antigen detection offers simple and fast operation but necessitates improved specificity. Nucleic acid detection, although being highly sensitive, has complex operation and high costs. Serological testing provides limited value for early diagnosis. Urine antigen detection, extensively employed globally, is limited to the detection of Legionella pneumophila serogroup I. Novel nucleic acid detection technologies, including digital PCR, isothermal amplification, and next-generation sequencing, present promising applications. Future research should aim to develop more streamlined, rapid, and sensitive detection methods to enhance the early diagnostic rate of Legionnaires’ disease.

Outbreaks and epidemics of RNA viruses represent a serious threat to human health. The retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs) signaling pathway plays a pivotal role in host resistance to viral infections. RLRs recognize the RNA produced after viral invasion, initiating the activation of the RLR signaling pathway to combat viral infection. Abnormal activation of this pathway is linked to the development of chronic inflammation, damage to immune organs, and autoimmune diseases. To prevent the disruption of RLR signaling pathway activation, the body has established a comprehensive regulatory system with the objective of stabilizing the RLR signaling pathway. Protein methylation represents a significant post-translational modification of proteins, playing a pivotal role in numerous biological processes. The methylation of molecules in the RLR signaling pathway has been demonstrated to be indispensable for the body to regulate the RLR signaling pathway. This paper presents a comprehensive review of the latest research findings on the role of protein methylation in regulation of the RLR signaling pathway, offering novel insights into the host regulation of the RLR signaling pathway in combatting viral infection.

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.

Non-alcoholic fatty liver disease (NAFLD) is a common chronic liver disease around the world, and it has a complex disease progression. Recent studies have demonstrated that gut microbiota (GM) plays a crucial role in the pathogenesis of NAFLD. The theory of gut-liver axis provides a theoretical basis for understanding the relationship between GM and the liver. Dysbiosis of GM leads to immune dysfunction, inflammatory responses, damaged gut barrier, and insulin resistance, all of which promote the development and progression of NAFLD. Furthermore, GM can participate in the development and progression of NAFLD through endotoxemia and abnormal metabolism of short chain fatty acids, bile acids, and choline. How to mitigate NAFLD by modifying GM has become the focus of current research, and the measures include fecal microbiota transplantation, probiotics, prebiotics, Chinese herbal medicines, and lifestyle interventions. The review focuses on the impact of the pathological state of GM on NAFLD and discusses the research progress in GM-targeted therapy for NAFLD. It is expected to provide new strategies and targets for the prevention and treatment of NAFLD.

Streptomyces are deeply studied and applied in the biocontrol of plant diseases. Streptomyces are widely distributed in soil, ocean and plant tissue. Streptomyces and the bioactive metabolites produced by Streptomyces exhibited antifungal, antibacterial, antivirus, nematicidal, pesticidal and herbicidal effects. The biocontrol mechanisms of Streptomyces against plant diseases, including antifungal activity, mycoparasitism, inducing resistance, enhancing plant growth, producing volatile organic compounds were summarized. The commercialized biocontrol agents developed based on Streptomyces were introduced. The research on Streptomyces-based biocontrol agents is limited in China, and the development and promotion of such agents could decrease the use of chemical fungicides and promote the environmental-friendly sustainable development of agriculture.

Akkermansia muciniphila, a major gut microorganism, has garnered significant attention for its involvement in the regulation of glucose and lipid metabolism. Glucose and lipid metabolic disorders, characterized by hyperglycemia and dyslipidemia, are caused by multiple factors. These disorders are not only prevalent globally but also increasingly common among young people in China, representing a major public health concern. This review systematically elaboratesthe research progress in A. muciniphila and glucose and lipid metabolism from the perspective of its mechanisms of action. Specifically, the review summarizes the regulatory pathways through which A. muciniphila influence glucose and lipid metabolism, assesses how pharmaceuticals that enhance A. muciniphila abundance affect metabolic parameters, and discusses advances in the bioengineering of A. muciniphila. By synthesizing current research findings, this review aims to provide valuable insights for understanding glucose and lipid metabolic disorders and developing novel therapeutic approaches for related diseases.

[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.

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.

Foot-and-mouth disease (FMD) is a highly contagious disease caused by foot-and-mouth disease virus (FMDV) in cloven-hoofed animals. FMDV is a single-stranded positive-sense non-enveloped RNA virus with icosahedral symmetry. FMDV can cause innate and adaptive immunity of the host, and it has evolved a variety of immune escape ways. The FMDV infection is a complicated process involving various host proteins. However, the related mechanisms remain largely unknown. Voltage dependent anion-selective channel 2 (VDAC2) is a mitochondrial channel protein, and the specific mechanism by which VDAC2 regulates FMDV replication remains unclear. [Objective] To confirm the regulatory effects between VDAC2 and FMDV and reveal the molecular mechanism by which VDAC2 inhibits FMDV replication. [Methods] The subcellular localization of VDAC2 was determined by the indirect immunofluorescence assay. The effects of FMDV on the translation and transcription levels of VDAC2 were determined by Western blotting and qPCR, respectively. The effect of VDAC2 overexpression on FMDV replication in BHK-21 cells was measured based on the virus titer. The effects of VDAC2 overexpression and knockdown on the levels of IL-1β, ISG15, OAS1, mtDNA, and gDNA during FMDV infection were evaluated by qPCR. [Results] VDAC2 was localized in the cytoplasm. FMDV infection down-regulated the expression of VDAC2. The overexpression of VDAC2 inhibited FMDV replication in a dose-dependent manner, while the knockdown of VDAC2 promoted FMDV replication. The overexpression of VDAC2 enhanced FMDV-induced interferon-I (IFN-I) response, while the knockdown of VDAC2 inhibited FMDV-induced IFN-I response. In addition, the overexpression of VDAC2 increased the release of mtDNA. [Conclusion] FMDV infection can downregulate the transcription and translation of VDAC2, as VDAC2 can exert antiviral effects by regulating mtDNA release and promoting the expression of antiviral factors such as IL-1β, ISG15, and OAS1. This study indicates that upon FMDV infection, host cells can regulate the virus replication by enhancing IFN-I response via VDAC2 to exert antiviral effects.

[Objective] To investigate the role of lmo2300 in oxidative stress resistance and infection of Listeria monocytogenes. [Methods] With L. monocytogenes 1/2 a serotype EGD-e as the parent strain, the lmo2300-deleted strain and complementary strain were constructed by homologous recombination. The growth, motility, oxidative stress resistance, minimum inhibitory concentration and reductase activity of Δlmo2300 were evaluated. The adhesion, invasion, proliferation, and intercellular migration abilities of the Δlmo2300 strain was assessed using cell models. The transcriptional levels of thioredoxin-related genes and major virulence genes in Δlmo2300 were detected with RT-qPCR. [Results] PCR identification and DNA sequencing confirmed the successful construction of Δlmo2300 and CΔlmo2300. Deletion of lmo2300 did not affect the bacterial growth, motility, antibiotic susceptibility, adhesion, invasion or intracellular proliferation. However, the Lmo2300 protein possesses reductase activity, and the transcriptional levels of the thioredoxin gene lmo1903 and grx are significantly upregulated in the Δlmo2300 mutant. And markedly improved resistance to oxidative substances, including H₂O₂, diamide, CdCl₂, and MnSO₄ compared with the wild type. The Δlmo2300 mutation significantly enhanced intercellular migration ability, accompanied by an approximately 8-fold upregulation of the actA gene transcription, which is consistent with the enhanced intercellular migration ability. [Conclusion] This study demonstrates that lmo2300 plays a critical role in modulating the oxidative stress resistance and intercellular migration of L. monocytogenes, providing novel insights into the infection biology and adaptive responses of L. monocytogenes to host-derived oxidative challenges.

Cotton Verticillium wilt, caused by the soil-borne fungal pathogen Verticillium dahliae, is a devastating disease that severely impacts global cotton production. [Objective] To investigate the biocontrol potential and mechanism of endophytic Pseudomonas sp. NWSUAF303 against cotton Verticillium wilt and provide novel microbial resources for managing soil-borne diseases in cotton. [Methods] The strain was identified by phylogenetic analysis based on 16S rRNA gene sequences and phenotypic characterization. Its antifungal spectrum was evaluated via dual-culture and volatile organic compounds (VOCs) inhibition assays. VOCs were detected by headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS). Pot experiments were carried out to assess the disease control efficacy of the strain. RT-qPCR and enzymatic activity assays were employed to elucidate the resistance mechanism of the strain against cotton Verticillium wilt. [Results] Strain NWSUAF303 was identified as Pseudomonas alvandae, exhibiting plant growth-promoting properties including nitrogen fixation, phosphate solubilization, and indole-3-acetic acid (IAA) production. Its non-volatile metabolites inhibited six phytopathogenic fungi, whereas VOCs demonstrated broader antifungal spectrum against seven pathogens, showing the inhibition rates >95% against Sclerotinia sclerotiorum and of 89.27% against V. dahliae 592. The VOCs of this strain downregulated the expression of virulence genes (VdPR1, Vdpf, and VdGAL4) in V. dahliae (P<0.05). Three key antifungal VOCs were identified, including 2,3-butanedione, 2-nonanol, and 6-methyl-2-heptanol, with the inhibitory effect of 2,3-butanedione on V. dahliae being first reported. Pot experiments revealed the control efficacy of 54.40% against Verticillium wilt, which was comparable to that of carbendazim. Strain NWSUAF303 activated the salicylic acid/jasmonic acid (SA/JA) signaling pathway, upregulating the expression of defense-related genes GhPAL, Gh4CL, and GhCHI (P<0.01), while enhancing the activities of peroxidase (POD), polyphenol oxidase (PPO), and superoxide dismutase (SOD). [Conclusion] P. alvandae NWSUAF303 combats Verticillium wilt through dual mechanisms: producing novel antifungal VOCs and activating systemic resistance via SA/JA signaling and defense enzyme coordination. With broad-spectrum antifungal activity and plant growth-promoting properties, this strain represents a promising biocontrol agent for sustainable management of cotton Verticillium wilt.

[Objective] To study the relieving effects and potential mechanisms of Lactiplantibacillus plantarum DY6 and the soybean meal fermented with this strain on constipation in mice and to develop non-toxic feed additives with probiotic potential. [Methods] Constipation was induced in male BALB/c mice by gavege of loperamide hydrochloride. The modeled mice underwent long-term feeding with the soybean meal fermented with DY6 or gavage with DY6 suspension. Linaclotide served as the positive control. We then systematically assessed the effects of fermented soybean meal on intestinal functions, immune factors, metabolic profiles, and gut microbiota in constipated mice. [Results] Compared with the model group, long-term intake of the soybean meal fermented with DY6 increased fecal moisture content and intestinal motility (P<0.05), ameliorated goblet cell reduction and lymphocyte aggregation in the colon tissue, lowered the serum levels of tumor necrosis factor-α, interleukin-6, and vasoactive intestinal peptide (P<0.05), and elevated the fecal levels of acetic acid and butyric acid (P<0.01). The fermented soybean meal modulated the gut microbiota structure. Specifically, the significantly enriched probiotics Odoribacter and Blautia were positively correlated with indicators of relieving constipation, while the significantly reduced pathogenic bacteria Helicobacter and Colidextribacter were negatively correlated with indicators of relieving constipation. [Conclusion] The soybean meal fermented with DY6 alleviates constipation by modulating the gut microbiota structure and metabolic profiles, restoring intestinal electrolyte homeostasis, and suppressing inflammation-associated signaling pathways. This intervention establishes novel applications and a theoretical framework for developing functional biological feed additives capable of both preventing and managing constipation in animals.

[Objective] To prepare secretory IgA (sIgA) antibody against foot-and-mouth disease virus (FMDV) and provide a new idea and basis for the comprehensive prevention and control of foot-and-mouth disease (FMD). [Methods] We constructed an eukaryotic expression plasmid harboring the heavy chain of IgA antibody by replacing the constant region gene of heavy chain of IgG with the codon-optimized corresponding region of IgA based on POA-8, a previously screened IgG neutralizing antibody capable of neutralizing both type O and type A FMDV. At the same time, the eukaryotic expression plasmids harboring the J chain and secretory component (SC) of pigs as well as the eukaryotic expression plasmid containing heavy chain, light chain, and J chain genes were constructed respectively. CHO-S cells were transiently co-transfected with 4 plasmids (heavy, light, J, and SC) or 2 plasmids (heavy+light+J and SC) for assembling and expression of sIgA antibody. sIgA antibody was purified and identified by SDS-PAGE and Western blotting. The binding activity and neutralizing activity of sIgA antibody against FMDV were evaluated by indirect ELISA and virus neutralization assay. [Results] sIgA antibody against FMDV could be successfully assembled and expressed after transfection of CHO-S cells with 4 or 2 plasmids. The binding and neutralizing abilities of sIgA against type O and type A FMDV were stronger than those of IgG. [Conclusion] This study established an efficient expression system for sIgA against FMDV, laying a foundation for the development of mucosal vaccines and antiviral drugs against FMDV in the future.

[Objective] To investigate whether Fusobacterium nucleatum promotes the development of lung cancer and find out the underlying mechanisms. [Methods] The cell experiment proved that F. nucleatum can promote the proliferation and metastasis of lung cancer cells; Animal experiments showed that F. nucleatum can promote the development of lung cancer; 16S rRNA gene sequencing of alveolar lavage fluid and transcriptome sequencing of lung tissue were performed to analyze the effects of F. nucleatum on the lung flora of mice with lung cancer and the activation of relevant pathways in lung tissue. [Results] The cell experiment showed that F. nucleatum significantly promoted the proliferation and metastasis of A549 cells. The animal experiments confirmed that F. nucleatum infection in the lungs increased the number of nodules and enhanced the fluorescence intensity in the lung tissue. The 16S rRNA gene sequencing revealed the enrichment of Muribaculum and Simplicispira in the lung of infected mice. The transcriptome sequencing results showed that the mouse model of lung cancer activated the interleukin-17 signaling pathway, cytokine-cytokine receptor interactions, Staphylococcus aureus infection pathway, tumor necrosis factor signaling pathway, and other signaling pathways related to inflammation or immunity after being infected with F. nucleatum. [Conclusion] F. nucleatum infection in mice with lung cancer disrupts the microbiota and activates the immunity- and inflammation-related signaling pathways in the lung, thereby promoting the metastasis of lung cancer in mice.

[Objective] To develop an efficient catalyst for organophosphorus pesticide degradation by immobilizing organophosphorus hydrolase (OPH) on the surface of Pichia pastorisvia the SpyCatcher/SpyTag (SpyC/SpyT) system, addressing the poor stability and low reusability of OPH in practical applications and providing a new method for the bioremediation of organophosphorus pesticide pollution. [Methods] The “bait protein” SpyCatcher (SpyC) was first displayed on the surface of P. pastoris, and the display efficiency was increased by increasing the copy number and optimizing the culture conditions. Then based on the specific interaction between SpyC and SpyT, OPH-SpyTag (OPH-SpyT) was efficiently displayed on the yeast surface. The thermal stability, pH stability, and reusability of immobilized OPH were evaluated, and the hydrolysis efficiency of immobilized OPH against methyl parathion, dimethoate, and chlorpyrifos was assessed. [Results] The display efficiency of SpyC on the P. pastoris surface reached over (97.0±0.4)%, with an optimized binding capacity of (21.4±0.7) mg green fluorescent protein for 1 g wet cells. OPH was successfully displayed on the cell surface via the SpyC/SpyT system. The immobilized OPH exhibited significantly enhanced thermal and pH stability, retaining more than 50% activity after five repeated uses. Under optimum conditions, the immobilized OPH showed the hydrolysis rates of (96.5±2.7)%, (79.5±2.3)%, and (82.6±2.8)% against 100 mg/L methyl parathion, dimethoate, and chlorpyrifos, respectively. This indicated that the method showed high hydrolysis efficiency for the organophosphorus pesticides. [Conclusion] The immobilization of OPH on P. pastoris surface via the SpyC/SpyT system effectively improves its stability and reusability, offering an efficient and environmentally friendly solution for the bioremediation of organophosphorus pesticide pollution. Meanwhile, this study provides a powerful tool and method for research in the field of P. pastoris surface display.

Sauropus androgynus has high medicinal and edible values. However, its growth is threatened by various viral diseases, which severely affect both the yield and quality of S. androgynus. Since research is limited regarding the viral diseases affecting S. androgynus in China. [Objective] To isotation, identifying the viral pathogens of S. androgynus in China. [Methods] The small RNA sequencing (sRNA-seq) data of S. androgynus leaves from our previous study were analyzed. RT-PCR was employed to detect the datura yellow vein virus (DYVV) in leaf samples of 10 different varieties of S. androgynus. With the total RNA of positive S4 leaves as a template, reverse transcription-polymerase chain reaction (RT-PCR), rapid amplification of cDNA ends (RACE), and Sanger sequencing were employed to determine the full-length genome sequence of the DYVV isolate from S. androgynus (named DYVV-sa). [Results] The analysis of the sRNA-seq data revealed the presence of DYVV in S. androgynus. RT-PCR detection of different varieties showed that only S4 and S12 tested positive for DYVV, and the full-length sequence of DYVV-sa was cloned based on S4. The genome of DYVV-sa was 13 185 nt in length and contained six open reading frames (ORFs). The DYVV-sa showed the identity as high as 95.8%-98.1% with the DYVV sequences isolated from Thunbergia alata. Moreover, the phylogenetic tree also demonstrated that DYVV-sa shared the closest genetic relationship with DYVV, clearly indicating that DYVV-sa was an isolate of DYVV. In addition, the majority of DYVV-sa virus-derived small interfering RNA (vsiRNA) were 21 nt and 22 nt, and those of 21 nt were more abundant. The first nucleotide at the 5′ termini of vsiRNAs derived from DYVV-sa preferred U and C. The proportion of vsiRNAs derived from the negative strand was higher than that from the positive strand. The distribution of vsiRNAs along the viral genome was generally even, with some hot spots formed in local regions. [Conclusion] This study found that DYVV can infect S. androgynus and successfully obtains the full-length genomic sequence of the DYVV-sa isolate. These findings expand the known natural host range of DYVV, provide crucial theoretical foundations for research on its genetic diversity and phylogenetic relationship, and offer clues for the prevention and control of viral diseases attacking S. androgynus.

Cyanobacteria, commonly known as blue-green algae, are important primary producers in aquatic ecosystems and common dominant algae causing algal blooms in freshwater. Cyanophages, especially procyanophages, are important planktonic ecological factors that affect the evolution of blue-green algae and aquatic microbial communities. Yet studies on procyanophages in cyanobacteria remain scarce. So far, few studies have reported the procyanophages in Microcystis. [Objective] To investigate the prevalence of lysogeny in Microcystis and characterize the genomic features of procyanophages in Microcystis. [Methods] All the 354 genome sequences of Microcystis spp. in GenBank were downloaded. PHASTER was used to predict procyanophage regions in the Microcystis genomes. Resistance and virulence factors in intact procyanophages and questionable procyanophages were annotated via the virulence factors of bacterial pathogens (VFDB) and comprehensive antibiotic resistance database (CARD). Bioinformatics tools were used for gene annotation and phylogenetic analysis of the procyanophages in Microcystis. Microcystis flos-aquae FACHB-1344 and M. aeruginosa FACHB-1326 each was predicted to harbor an intact procyanophage by PHASTER. To evaluate the infection activities of these two procyanophages, mitomycin C induction assays and dot-ELISA were conducted. [Results] Among all the 354 Microcystis genomes, 98.3% were predicted to harbor intact procyanophages, questionable or imcomplete procyanophages. A total of 13 intact procyanophages, 5 questionable procyanophages and 725 incomplete procyanophages were predicted by PHASTER. The 13 intact procyanophages and 5 questionable procyanophages were named as WZ1-WZ13 and YS1-YS5, respectively. No antibiotic resistance or virulence gene was detected in them. The phylogenomic tree displayed distant evolutionary relationships between the 18 procyanophages and other known viruses. Bioinformatics analysis suggested that YS5 revealed a previously unknown novel genus. WZ2, WZ3, WZ4, WZ5, WZ6, WZ7, WZ9, WZ10, WZ11, WZ12 and YS3 together revealed a novel family. WZ1 and YS1 together revealed a novel family. YS2, YS4, WZ8 and WZ13 each revealed a novel family. The procyanophages in M. flos-aquae FACHB-1344 and FACHB-1326 were verified to be activated by mitomycin C. [Conclusion] Lysogeny widely exists in Microcystis spp. The novel procyanophages in Microcystis spp. unlock novel viral evolutionary lineages previously unknown. This study enriches the understanding about cyanobacterium-virus interactions and the diversity of aquatic viruses.

[Objective] To investigate the role of dppC2 in the survival of Yersinia pestis in macrophages. [Methods] The strain (201-ΔdppC2) with traceless knockout of dppC2 was constructed with a suicide plasmid via homologous recombination based on Y. pestis biovar Microtus strain 201. Phenotypes were compared between 201-ΔdppC2 and the wild type (201-WT) by the acid survival assay, hydrogen peroxide survival assay, macrophage intracellular survival assay, reactive oxygen species (ROS) detection, and cytotoxicity and mouse challenge assays. The gene expression was compared between 201-ΔdppC2 and 201-WT by transcriptomics analysis and RT-qPCR. [Results] Compared with 201-WT, 201-ΔdppC2 exhibited multiple phenotypic alterations, including significantly increases in intracellular survival rates in RAW264.7 and THP-1 cells and under acidic and hydrogen peroxide conditions, upregulation of the acid resistance gene hdeD and the catalase-related genes katA and katG, enhancement of catalase and peroxidase activities, and declines in intracellular ROS levels in 201-ΔdppC2 and RAW264.7 cells infected with the mutant. Furthermore, 201-ΔdppC2 showed reduced cytotoxicity to HeLa cells but no change in the virulence in mice. [Conclusion] The deletion of dppC2 has been demonstrated to enhance the fitness of Y. pestis to acidic and hydrogen peroxide environments, which promote the survival and replication of Y. pestis in macrophages.

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 study the effect of ferulic acid on the laccase activity of Dichomitus squalens and its molecular mechanism, providing a theoretical basis for microbial degradation of aromatic compounds. [Methods] Ferulic acid was added to the synthetic medium at different concentrations to investigate its effects on the growth of D. squalens and laccase activity. Transcriptomic and proteomic analyses were performed to examine the changes in laccase transcription and protein expression levels induced by ferulic acid. The lcc3 gene was knocked down using RNAi technology, and the impact on laccase activity and the ability to degrade various aromatic compounds was assessed. A self-constructed dual-luciferase system based on Gaussia luciferase and Nano luciferase was employed to identify the core promoter region of the lcc3 gene. [Results] An appropriate concentration of ferulic acid can significantly enhance laccase activity in D. squalens. Transcriptomic and proteomic analyses revealed that the transcription and expression levels of the lcc3 gene were markedly up-regulated under ferulic acid induction. In the lcc3-gene-knocked-down strain, both laccase activity and the ability to degrade various aromatic compounds decreased significantly, confirming that lcc3 is a key gene for laccase-related activities in degrading aromatic compounds in D. squalens. Moreover, the dual-luciferase system successfully identified the core promoter region of the lcc3 gene. [Conclusion] This study first revealed that ferulic acid can induce D. squalens laccase activity and clarified the molecular mechanism. It was also proved that lcc3 is a key gene for ferulic acid-induced laccase activity and degradation of aromatic compounds in D. squalens. Identifying the core promoter region of lcc3 lays a foundation for gene expression regulation research, and these findings offer theoretical support for using microbial laccases to degrade aromatic compounds.

[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.

Nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR) are two precursors of the redox coenzyme nicotinamide adenine dinucleotide (NAD). Due to their ability to effectively increase NAD levels without toxic side effects, they have garnered significant attention. [Objective] This study employed an integrated approach combining metabolomics and 16S rRNA gene sequencing to investigate and compare the effects of NMN or NR supplementation on growth performance, intestinal health, gut microbiota, and metabolites in mice. [Methods] Male C57 mice were randomly allocated into a control group and two experimental groups. The experimental groups received drinking water supplemented with NMN or NR via gavage. Non-targeted metabolomics analysis and 16S rRNA gene sequencing were conducted to systematically investigate the alterations in endogenous metabolites and gut microbiota composition. Furthermore, the expression levels of associated factors were quantified by PCR. [Results] Compared with the control group, supplementation with NMN or NR increased the richness and diversity and improved the composition of gut microbiota in mice, with NMN showing greater efficacy. Additionally, both NMN and NR supplementation significantly upregulated the expression levels of metabolites associated with anti-inflammatory and antioxidant activities. PCR results indicated that both NMN and NR suppressed the expression of pro-inflammatory cytokines. Furthermore, NMN supplementation significantly increased the number of goblet cells in the colon, thereby enhancing the intestinal barrier function. [Conclusion] Dietary supplementation with NMN or NR improves the gut microbiota composition in mice, elevates the levels of beneficial metabolites, and inhibits the expression of pro-inflammatory cytokines.

Obligate symbiotic bacteria in the human gut play a key role in maintaining microecological balance and are generally thought to be transmitted vertically across generations through breastfeeding. However, compared with that on Bifidobacterium, there is limited literature on the transmission and diffusion mechanisms of Bacteroides, a representative of obligate symbiotic microbiota in the human body, within populations. Additionally, the occurrence and cross-generational transmission of Bacteroides within families remain poorly understood. [Objective] We explored the vertical transmission and co-occurrence patterns of Bacteroides among family members, aiming to reveal the assembly mechanism of gut microbiota in the human body and provide a theoretical basis for the recommendation of microbiome-based interventions and the realization of personalized gut regulation. [Methods] A high-throughput sequencing dataset for Bacteroides-specific rpsD in fecal samples from four families with 50 members in 3-4 generations in Xinjiang, China was established. Then, the composition and diversity of Bacteroides communities among different families and member groups were measured at the species level and amplicon sequence variant (ASV) level by comparison and annotation. [Results] A total of 16 Bacteroides species and 3 704 ASVs were identified, of which 1 293 ASVs were common among the four families. The five species with the highest number of ASVs were B. fragilis (653), B. ovatus (619), B. uniformis (507), B. caccae (463), and B. finegoldii (314), which were also the five species with the highest relative abundance and prevalence. There were significant differences in community composition and abundance of Bacteroides among families, with B. fragilis, B. uniformis, and B. faecichinchillae being the most significant representatives. There was no significant difference in alpha or beta diversity among family members grouped according to gender and age (P>0.05). By contrast, the beta diversity analysis based on Bray-Curtis distance showed differences between families (P=0.001). According to the sharing rate of ASVs and Bray-Curtis distance, the Bacteroides strain similarity of mother-child and siblings was significantly higher than that of father-child, couple, and unrelated members. [Conclusion] The community structure and diversity of Bacteroides were characterized by family convergence, with significant differences among families. The similarity of Bacteroides strains was the highest within the mother-child and sibling groups among different social relationship groups, supporting transgenerational vertical transmission at the strain level. The conclusion remains to be validated by the combination of the strain isolation method and metagenomic sequencing.

[Objective] To achieve efficient expression of the alkaline laccase PIE5 in Coprinopsis cinerea with molasses as a substitute for glucose as the carbon source. [Methods] We enhanced the laccase production in C. cinerea by either exogenous addition of the invertase GspInv or endogenous co-expression of GspInv to hydrolyze sucrose in molasses. The fermentation conditions were optimized based on the laccase activity. [Results] With 40 g/L molasses as the carbon source, strain CcPIE5-14 achieved the laccase activity of (11.9±1.2) U/mL, while sucrose remained unutilized in the fermentation liquid. Upon addition of exogenous GspInv, sucrose in the fermentation liquid was hydrolyzed into fructose and glucose, and strain CcPIE5-14 exhibited the peak laccase activity of (14.8±0.7) U/mL in the medium with 30 g/L molasses. Co-expression of GspInv in CcPIE5-14 generated the engineered strain CcPIE5-14-GspInv-12, which demonstrated the maximum laccase activity of (28.1±2.4) U/mL in the mKjalke medium. When using molasses as the carbon source for laccase production, strain CcPIE5-14-GspInv-12 achieved the peak laccase activity of (20.1±2.7) U/mL, which represented a 2.24-fold increase over that of the parental strain CcPIE5-14. Following fermentation condition optimization, strain CcPIE5-14-GspInv-12 attained the maximum laccase activity of (44.6±2.6) U/mL, which marked a 2.22-fold enhancement over the pre-optimization level. [Conclusion] The engineered strain CcPIE5-14-GspInv-12, co-expressing laccase and invertase, demonstrates efficient production of the alkaline laccase PIE5 in C. cinerea with cost-effective molasses as the carbon source.

UvrY is a key response regulator of the BarA/UvrY two-component system (TCS) and plays an important role in regulating bacterial virulence and environmental adaptability. [Objective] To investigate the regulatory role of UvrY in the biological characteristics and pathogenicity of Vibrio parahaemolyticus SH112. [Methods] The uvrY-deleted mutant (ΔuvrY) and its complementary strain (CΔuvrY) were constructed by homologous recombination. Phenotypes were systematically compared among the wild type, mutant, and complementary strains by growth curve plotting, motility (swimming and swarming) assays, biofilm formation assay, bacterial competition assay, HeLa cell adhesion and cytotoxicity assays, as well as a mouse infection model (analysis of bacterial loads in tissues and lethality). [Results] Compared with the wild type strain, ΔuvrY exhibited significant growth defects during the late exponential phase and weakened motility, with swimming and swarming reduced by 33% and 70%, respectively, while the biofilm formation of the mutant remained unaffected. Additionally, ΔuvrY showed weakened competitive inhibition against Escherichia coli, a 36.7% reduction in HeLa cell adhesion, and a 15.8% decrease in cytotoxicity. Mouse infection experiments further demonstrated that ΔuvrY had significantly reduced tissue colonization capacity and the attenuation of 75% in pathogenicity. [Conclusion] This study reveals that UvrY plays a crucial role in the pathogenicity of V. parahaemolyticus by regulating the growth, motility, competitive ability, and interaction with the host, giving insights into the regulatory network of the BarA/UvrY two-component system.

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.

[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.

[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.

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] To investigate the antimicrobial resistance phenotypes and genomic characteristics of Salmonella Wandsworth isolates from fecal and bedding samples across four dairy farms in Jiangsu. [Methods] Serotyping was reconfirmed by the slide agglutination method, and antimicrobial susceptibility was determined via the Kirby-Bauer disk diffusion assay. Whole-genome sequencing was performed, followed by bioinformatics analysis to characterize multilocus sequence typing (MLST) profiles, antimicrobial resistance genes, and virulence genes. A phylogenetic tree was built based on core genome single nucleotide polymorphisms (SNPs) to assess genetic homology among strains and elucidate population evolutionary relationships between prevalent strains from diverse sources. [Results] Seven Salmonella Wandsworth isolates were identified, all exhibiting susceptibility to 14 tested antimicrobials. The isolates were identified as ST1498 by MLST, harboring the aminoglycoside resistance gene aac(6')-Iaa and 106 virulence genes spanning eight functional categories. The analysis of SNPs revealed high genetic homogeneity, with six isolates clustering closely and three isolates showing a difference of zero in SNPs. [Conclusion] This study isolated a rare ST1498-type Salmonella Wandsworth from dairy farms in Jiangsu. The isolates demonstrate susceptibility to all tested antimicrobials while harboring a resistance gene and multiple virulence genes. These findings highlight the necessity of enhanced Salmonella surveillance in dairy farms to mitigate potential epidemiological risks.