Marek’s disease (MD), caused by the oncogenic Marek’s disease virus (MDV), is a highly contagious avian infection that induces lymphoproliferative tumors. The RNA-binding protein ELAVL1 is known to regulate tumor cell proliferation and apoptosis, but its role in MDV-induced oncogenesis remains unclear. This study investigated whether ELAVL1 modulates proliferation and apoptosis in the MDV-transformed MSB1 cell line and whether its effects involve the cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2) pathway. MSB1 cells were transiently transfected with ELAVL1-overexpressing plasmids (pEGFP-C-ELAVL1) or ELAVL1-specific siRNA, with expression confirmed by real-time PCR (qRT-PCR). Cell proliferation was assessed using the CCK-8 assay, while cell cycle distribution and apoptosis rates were analyzed by flow cytometry. COX-2 and PGE2 expression levels were determined by qRT-PCR, Western blotting, and ELISA. Overexpression of ELAVL1 significantly promoted the proliferation of MSB1 cells, decreased transition into the G1 phase, increased the proportions of S and G2 phase cells, and suppressed apoptosis. Correspondingly, both mRNA and protein levels of COX-2 and PGE2 were significantly elevated. Conversely, ELAVL1 knockdown significantly inhibited proliferation, induced G1 phase arrest, decreased S phase cells, and significantly decreased COX-2 and PGE2 expression. These findings indicate that ELAVL1 promotes proliferation and inhibits apoptosis in MDV-transformed MSB1 cells, potentially via the COX-2/PGE2 signaling pathway.

The type VI secretion system (T6SS) is an important fitness determinant of Salmonella enterica serovar Typhimurium (S. Typhimurium) during host colonization and bacterial competition. Tldi1 has been identified as an immunity protein associated with a T6SS antibacterial toxin-immunity module, but its contribution to avian infection remains unclear. This study investigated whether Tldi1 affects the infection outcome of S. Typhimurium in young chickens. Three-day-old Hy-Line Brown chickens were challenged with the wild-type strain SL1344, a tldi1 deletion mutant, or a complemented strain. Clinical signs, body weight, liver and spleen indices, splenic bacterial loads, tissue pathology, cecal mucin staining, inflammatory cytokine expression, intestinal barrier-related gene expression, and cecal microbiota composition were evaluated. Compared with wild-type infection, the tldi1 deletion mutant caused milder clinical signs, lower liver and spleen indices, reduced splenic bacterial loads, and attenuated histopathological lesions in the liver, spleen, ileum, and cecum. The mutant also induced lower expression of several pro-inflammatory cytokine genes and partially alleviated the downregulation of intestinal barrier-related genes. Complementation of tldi1 largely restored the wild-type infection phenotype. Cecal 16S rRNA sequencing showed that tldi1 deletion was associated with altered microbial community features and reduced inter-individual dispersion; however, overall beta-diversity differences were not statistically significant. These findings indicate that Tldi1 contributes to the in vivo fitness and infectionassociated pathology of S. Typhimurium in chickens. The results provide a basis for further investigation of T6SS toxin-immunity modules as potential targets for controlling Salmonella infection in poultry.

Ochratoxin A (OTA), a secondary metabolite produced by Penicillium and Aspergillus species, contaminates food and feed globally, posing serious threats to both livestock and human health. Among current detoxification strategies, probiotic-based degradation of OTA has emerged as a key research focus. This study aimed to isolate safe probiotic strains with high OTA-detoxifying efficacy to support their potential application in feed and food industries. A total of 57 bacterial strains were isolated from environmental samples, including soil, moldy feed, and animal feces. Among these, a novel strain identified as Bacillus amyloliquefaciens MM28 demonstrated strong OTA-degrading activity, removing 86.31% of OTA (0.4 µg/mL) within 48 h. Whole-genome analysis indicated that B. amyloliquefaciens MM28 harbors functional genes related to glucose metabolism, membrane transport, and properties associated with antibacterial, antioxidant, and immunomodulatory activities, suggesting multiple beneficial traits. In a 28-day chronic exposure study, mice were administered B. amyloliquefaciens MM28 via gavage (1 × 108 CFU/mL). Results showed that both female and male mice in the MM28 group exhibited higher body weight and improved growth performance compared to the PBS control group. Furthermore, intestinal morphology was enhanced in the MM28 group, as indicated by greater villus length and villus-length-to-crypt-depth ratio. The expression of proinflammatory cytokines was also reduced in the treated animals. Moreover, analysis of gut microbiota composition revealed that MM28 supplementation led to an increased abundance of Bacteroides and Desulfovibrio, alongside a reduction in Lachnospira and Oscillospira. In conclusion, this study demonstrates that Bacillus amyloliquefaciens MM28 is a safe and efficient strain capable of degrading OTA. These findings highlight its promising potential as a biological detoxifying agent in food and feed industries.

IntroductionType VI secretion system (T6SS) is a key bacterial secretion device in Salmonella enterica serovar Typhimurium (S. Typhimurium), responsible for translocating effectors to mediate bacterial-host interaction. Tldi1, a well-characterized immunity protein encoded in the T6SS gene cluster, specifically neutralizes the cognate toxin Tlde1 to prevent bacterial “friendly fire”. However, there is still a lack of systematic and in-depth research on the functions of Tldi1 at present. In order to elucidate the phenotype and toxicity effects of Tldi1 deficiency on S. Typhimurium, this study used S. Typhimurium SL1344 as a model strain and explored the role of Tldi1 toxicity on bacterial ecological adaptability and infection process through multi-level experiments.MethodsFirstly, molecular bioinformatics approaches were employed to analyze the physicochemical properties, hydrophilicity, hydrophobicity, transmembrane regions, subcellular localization, as well as secondary and tertiary structures of the Tldi1 protein. Secondly, a tldi1-deficient mutant of S. Typhimurium was constructed via homologous double crossover recombination, and alterations in its biological characteristics were analyzed. Finally, a mouse infection model was used to investigate the effect of tldi1 deletion on the infection progression of S. Typhimurium.ResultsThe results showed that compared with the wild-type (WT) strain, the Δtldi1 strain exhibited reduced splenic colonization, and regulated host inflammation, while these phenotypes were reversed in the Δtldi1/pΔtldi1 strain.DiscussionTldi1, as a key immunity protein for Tlde1 neutralization, indirectly regulates the environmental adaptability and host immune homeostasis of S. Typhimurium, providing new insights into the function of T6SS immunity proteins.

IntroductionDeoxynivalenol (DON), a prevalent mycotoxin in grains and feed, poses a serious threat to animal health by inducing intestinal dysfunction. While some probiotics are known to mitigate DON toxicity, the multifaceted protective effects of Lactobacillus rhamnosus MY-1—a strain with high DON-degradation capacity and a proven safety profile—require comprehensive evaluation. This study aimed to systematically assess the ability of MY-1 to alleviate DON-induced oxidative stress, inflammation, and gut microbiota dysbiosis, and to elucidate its underlying mechanisms.MethodsInvestigations were conducted in vitro using IPEC-J2 cells and in vivo using a BALB/c mouse model. We examined the effects of MY-1 on cell viability, ultrastructure, oxidative stress markers (MDA, T-AOC), inflammatory cytokines (TNF-α, IL-1α, IL-4), apoptosis-related genes (BAX, Caspase-3, BCL-2), and tight junction protein (ZO-1, Occludin, Claudin-1) expression. Gut microbiota composition was analyzed via alpha (Chao1, Simpson, Shannon) and beta diversity indices.ResultsThe MY-1 supernatant restored IPEC-J2 cell viability and ameliorated DON-induced ultrastructural damage. MY-1 alleviated oxidative stress by reducing MDA and enhancing T-AOC, while inhibiting pro-inflammatory cytokines (TNF-α, IL-1α) and promoting the anti-inflammatory cytokine IL-4. In mice, MY-1 mitigated DON-induced growth inhibition and intestinal pathological damage, restored tight junction protein expression, and regulated apoptosis-related genes. Gut microbiota analysis showed that MY-1 reversed DON-induced dysbiosis, restoring alpha diversity and beta diversity structure, and modulated the abundances of dominant genera such as Bacteroides and Dubosiella.DiscussionThis study demonstrates that Lactobacillus rhamnosus MY-1 exerts comprehensive protective effects against DON-induced intestinal toxicity through integrated mechanisms, including direct detoxification, antioxidant and anti-inflammatory activities, and microbiota modulation. These findings underscore the value of MY-1 as a well-characterized probiotic candidate for mitigating mycotoxin effects in animal production.

Quorum sensing (QS) and the Type VI Secretion System (T6SS) constitute major regulatory and effector modules that, in numerous Gram-negative bacteria, couple bacterial communication with contact-dependent secretion. A growing body of evidence suggests that these systems are interconnected via multilayered regulatory networks, as opposed to a single universal circuit. Specifically, QS can govern T6SS expression through LuxR-family regulators, Qrr small RNAs, RpoN, cyclic di-GMP, and biofilm-associated spatial cues. Conversely, T6SS activity can indirectly modulate QS outputs by reshaping local community composition, restricting QS-defective mutants, or altering the proportions of signal-producing and signal-responding populations. The direction, magnitude, and biological outcomes of these interactions are highly contingent upon species, T6SS subtype, strain background, ecological niche, and experimental model. In this review, we synthesize the current body of evidence for direct and indirect QS-T6SS crosstalk, critically appraise unresolved controversies and knowledge gaps, and discuss how this regulatory interface might guide the development of anti-virulence strategies that target both bacterial communication and contact-dependent secretion.

Listeria monocytogenes (L. monocytogenes) is a significant zoonotic pathogen responsible for listeriosis, a foodborne infection with high mortality. The inflammasome, an innate immune complex, plays a critical role in controlling pathogenic infections through its rapid inflammatory output. During L. monocytogenes infection, pore-forming toxins such as listeriolysin-O and flagellin are quickly recognized by pattern recognition receptors (PRRs), triggering inflammatory responses and activating the host’s anti-infection immunity. However, excessive or chronic inflammasome activation and subsequent interleukin-1β (IL-1β) release are implicated in the pathogenesis of L. monocytogenes. Although inflammasome activation is an effective defense against L. monocytogenes, the bacterium has evolved multiple mechanisms to inhibit this immune pathway. Hence, research on inflammasomes activation is crucial for better understanding the pathogenic mechanism of L. monocytogenes. In this review, we highlight recent advances in the understanding of the molecular mechanisms of inflammasome activation by L. monocytogenes infection. We then discuss advances in the role of the inflammasome pathway in the pathogenesis of L. monocytogenes, along with an overview of the applications of inflammasome inhibitors. Extensive studies into the mechanisms by which L. monocytogenes activates the inflammasome could lead to the discovery of novel therapeutic targets and strategies to fight L. monocytogenes infections.

L-arabinose is a natural pentose sugar widely present in plant cell walls and agricultural residues. It functions both as a carbon source and a signaling molecule, endowing it with significant potential for applications. This article reviews the sources, microbial metabolism, and signal transduction pathways of L-arabinose, with a focus on its regulatory roles and mechanisms in the gut ecosystem and the plant rhizosphere microenvironment. In the gut, L-arabinose modulates microbiota composition, repairs the intestinal barrier, maintains water and salt balance, and influences gastrointestinal hormones and neurotransmitters, thereby inhibiting foodborne pathogens and alleviating constipation. In the plant rhizosphere, L-arabinose activates defense pathways, enhances crop resistance against pathogens, and improves the disease-suppression ability of biocontrol agents. This review aims to provide a theoretical foundation for developing L-arabinose-based functional food ingredients and sustainable crop protection strategies, offering innovative approaches to improve the safety and resilience of food systems.

Deoxynivalenol (DON), a thermostable mycotoxin from Fusarium, threatens livestock intestinal health via oxidative stress, inflammation, and growth inhibition. Microbial detoxification is promising, but most reported strains lack systematic evaluation of probiotic functionality, biosafety, and in vivo benefits. This study aimed to screen a safe, multifunctional probiotic that efficiently degrades DON and improves gut health. Bacillus velezensis YK-19, isolated from porcine intestinal contents, degrades DON by 93.79%. The strain exhibits excellent tolerance to acid, bile salts, heat, and gastrointestinal conditions, along with biofilm formation, surface hydrophobicity, auto-/co-aggregation, and multiple digestive enzyme secretion. In a 28-day gavage safety study in mice, YK-19 administration was associated with reduced baseline expression of pro-inflammatory cytokines (IL-6, IL-1β, TNF-α) and upregulated tight junction genes (ZO-1, Claudin-1, E-cadherin) in intestinal tissues, suggesting immunomodulatory activity under non-challenged conditions. Gut microbiota analysis confirmed that YK-19 maintained diversity and structural stability without dysbiosis. Genomic analysis revealed enrichment in carbohydrate metabolism, transport systems, and secondary metabolite biosynthesis genes. In conclusion, Bacillus velezensis YK-19 is a safe and efficient probiotic candidate for DON degradation, providing a theoretical basis for the prevention and control of DON contamination.

In Salmonella, the type III and type VI secretion systems (T3SS and T6SS) play critical roles in pathogenicity. The bacterium harbors two distinct T3SSs: T3SS-1, encoded by SPI-1, promotes host cell invasion, whereas T3SS-2 (located within SPI-2) facilitates systemic infection. Both systems translocate effector proteins that disrupt normal host cell functions. Meanwhile, the T6SS enhances competitive fitness in the gut by targeting rival bacteria and supports evasion of the host immune response. Recent evidence indicates that these secretion systems share common regulatory components, including the PhoP-PhoQ and PmrA-PmrB two-component systems, as well as signaling molecules such as cyclic di-GMP (c-di-GMP), allowing coordinated activation and functional adaptation during infection. However, the precise mechanisms governing their crosstalk remain poorly understood. This review summarizes the current knowledge of the composition, function, and regulation of T3SS and T6SS in Salmonella, examines their interplay, and provides perspectives for future research into pathogenesis.

Mannheimia haemolytica (M. haemolytica) cause mastitis in sheep, acute sepsis in newborn lambs, and co-infections with various pathogens, leading to bovine respiratory disease syndrome (BRDS), these infections have resulted in significant economic losses to both domestic and international farming industries. An in-depth understanding of the pathogenic mechanisms of M. haemolytica is crucial for the prevention and control of this disease. Outer membrane vesicles (OMVs) play a vital role in bacterial pathogenesis, serving as key mediators of interactions between Gram-negative bacteria and their hosts. However, the specific role of OMVs in the pathogenic process of M. haemolytica remains poorly understood. To address this, we isolated OMVs from the Mannheimia haemolytica Type A5 strain (MH-5) using ultracentrifugation and subsequently characterized their secretory properties, protein composition, and immunogenicity through electron microscopy, liquid chromatography-tandem mass spectrometry (LC-MS/MS), and cellular experiments. The electron microscopy results indicated that the MH-5 strain secreted OMVs under natural growth conditions. Proteomic and bioinformatics analyses revealed that these OMVs contained 282 proteins, with significant enrichment in proteins related to immunity, iron metabolism, and catalytic activity. Cellular experiments demonstrated that, compared to the control group, the OMVs group exhibited a significant increase in the mRNA expression of IL-1β, IL-6, and TNF-α, with secretion levels increasing in a dose-dependent manner, thereby enhancing the inflammatory response. These findings lay the groundwork for further exploration of the role of OMVs in the pathogenesis of M. haemolytica and provide insights for the development of effective vaccines and antibiotics against this pathogen.

The type VI secretion system (T6SS) is a specialized protein complex in Gram-negative bacteria that delivers toxic effector molecules into target cells. However, the role of ClpV-a critical ATPase involved in T6SS assembly in Salmonella pathogenesis remains poorly understood. In this study, we investigated the contribution of ClpV to environmental stress resistance and virulence in Salmonella enterica serovar Typhimurium (S. Typhimurium). Our findings demonstrate that ClpV significantly influences the ability of S. Typhimurium strain SL1344 to with stand various stressors, including bile salts, acidic conditions, hydrogen peroxide, and ethanol. Furthermore, ClpV enhances the competitive fitness of S. Typhimurium against commensal gut bacteria. Notably, ClpV appears to play a crucial role in pathogenicity by modulating the gut environment, disrupting microbial homeostasis, and facilitating bacterial persistence in host niches. These results provide a foundation for future studies on the molecular mechanisms by which T6SS mediates gut colonization and chronic infection in S. Typhimurium.

TatD is evolutionarily conserved in a variety of organisms and has been implicated in DNA repair, apoptosis, and the disruption of extracellular traps. The aim of our study was to investigate the effects of TatD on L. monocytogenes biofilms. In our previous study, the deletion of the TatD gene from L. monocytogenes (named LmTatD) increased biofilm formation. However, the underlying mechanism remains unclear. In this study, we present a detailed analysis of the structural characteristics of TatD. Bioinformatic analysis revealed that the amino acid residues DPGEGDQHEDP are fully conserved. LmTatD belongs to the Class II TatD family (TATDN3) and contains a signal peptide. Recombinant LmTatD exhibited DNase activity regardless of the DNA substrate. Mutagenesis experiments confirmed the importance of glutamic acid, histidine, and aspartic acid residues in enzymatic activity. Biofilm formation was evaluated via a crystal violet assay, confocal laser scanning microscopy, and scanning electron microscopy. rLmTatD impaired biofilm formation and reduced eDNA levels without disrupting the integrity of the bacteria within biofilms. Moreover, deficiency of LmTatD led to a significant decrease in the DNase activity of the extracellular proteins from L. monocytogenes, whereas there was an increase in biofilm formation and eDNA production during the dispersion stage. However, no significant change in the total number of biofilm or planktonic bacteria was observed at any of the time points. Additionally, the mRNA level of LmTatD in the biofilm formed by the wild-type strain at the dispersion stage was greater than that at the attachment and maturation stages. The number of planktonic bacteria for the wild-type strain at the dispersion stage was significantly greater than that for the ΔLmTatD mutant. Collectively, these data suggest that LmTatD exhibits extracellular DNase activity and regulates L. monocytogenes biofilm dispersion.

Background: Enterotoxigenic Escherichia coli (ETEC) is a zoonotic pathogen causing diarrhea and mortality in infants and livestock. Its numerous serotypes necessitate the urgent development of multivalent vaccines for effective prevention, thereby reducing public health and economic threats. Methods: Computational bioinformatics analyses were conducted on five major ETEC adhesins structural subunits (FaeG, FanC, FasA, FimF41a, and FedF). Dominant epitopes were selected and concatenated via flexible linkers, incorporating the PADRE sequence and LTb adjuvant to design a multi-epitope fusion antigen (MEFA). The recombinant MEFA protein was expressed in a prokaryotic system. Furthermore, molecular dynamics simulations, docking, and immune simulations assessed structural stability and immunogenicity. Immunoreactivity was tested by Western blot. Murine immunization evaluated antibody responses, lymphocyte proliferation, cytokine secretion, and protection against ETEC challenge. Results: Structural modeling showed an extended conformation, with docking and simulations indicating strong immune activation. Western blot confirmed MEFA immunoreactivity. MEFA induced high antigen-specific antibody titers, enhanced splenocyte proliferation, and increased IFN-γ and IL-4 secretion, indicating a Th2-biased response in mice. Vaccinated mice survived lethal ETEC challenge and maintained intestinal integrity. Conclusions: The MEFA candidate vaccine effectively induces robust humoral and cellular immune responses and provides protection against ETEC infection, representing a promising strategy for next-generation multivalent ETEC vaccines.

Bovine Viral Diarrhea Virus (BVDV) is a major pathogen associated with calf diarrhea and reproductive disorders in cattle. This study evaluated the immune-protective potential of a subunit vaccine based on the capsid C protein of the BVDV HNL-1 strain. In mice model, the C protein subunit vaccine exhibits a favorable safety and elicits robust immune-protective efficacy comparable to commercial inactivated vaccines. Immunized mice exhibited a significant increase in serum anti-C protein IgG antibodies (P < 0.01) and a neutralizing antibody response. The vaccine effectively stimulated both Th1 and Th2 immune responses, as indicated by elevated levels of IFN-γ and IL-4 (P < 0.01). Following viral challenge, substantial reductions in viral loads were observed across multiple tissues (liver, kidney, spleen, lungs, duodenum), as·well as in blood, and feces (P < 0.01). Histopathological analysis revealed markedly attenuated organ damage, reduced apoptosis of intestinal epithelial cells (P < 0.05), and significant increases in goblet cell numbers and expression of tight junction proteins (ZO-1/Occludin) (P < 0.01), indicating effective preservation of the intestinal mucosal barrier. Together, these findings collectively demonstrate that the C protein subunit vaccine confers protection through dual mechanisms: activation of both humoral and cellular immune response, and maintenance of intestinal barrier integrity. This vaccine candidate represents a promising strategy for controlling BVDV and provides a foundation for the development of novel vaccines.

Malignant tumors are prevalent with high mortality rates in humans, dogs, and cats. Some microorganisms have been shown to inhibit cancer progression. The objective of this study is to evaluate the inhibitory effects of Neospora caninum, a livestock parasite, on three different tumor models in C57BL/6 mice, including Lewis subcutaneous tumors, Lewis and B16F10 melanoma lung metastasis. The results showed that a sufficient amount of N. caninum tachyzoites can significantly inhibit the development of subcutaneous tumors and lung metastasis (P < 0.001), and induce more than 50

Mycotoxins are secondary metabolites produced by several fungi and moulds that exert toxicological effects on animals including immunotoxicity, genotoxicity, hepatotoxicity, teratogenicity, and neurotoxicity. However, the toxicological mechanisms of mycotoxins are complex and unclear. The nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family pyrin domain containing 3 (NLRP3) inflammasome is a multimeric cytosolic protein complex composed of the NLRP3 sensor, ASC adapter protein, and caspase-1 effector. Activation of the NLRP3 inflammasome plays a crucial role in innate immune defence and homeostatic maintenance. Recent studies have revealed that NLRP3 inflammasome activation is linked to tissue damage and inflammation induced by mycotoxin exposure. Thus, this review summarises the latest advancements in research on the roles of NLRP3 inflammasome activation in the pathogenesis of mycotoxin exposure. The effects of exposure to multiple mycotoxins, including deoxynivalenol, aflatoxin B1, zearalenone, T-2 toxin, ochratoxin A, and fumonisim B1, on pyroptosis-related factors and inflammation-related factors in vitro and in vivo and the pharmacological inhibition of specific and nonspecific NLRP3 inhibitors are summarized and examined. This comprehensive review contributes to a better understanding of the role of the NLRP3 inflammasome in toxicity induced by mycotoxin exposure and provides novel insights for pharmacologically targeting NLRP3 as a novel anti-inflammatory agent against mycotoxin exposure.

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a common foodborne enteric pathogen that infects humans or mammals and colonizes the intestinal tract primarily by invading the host following ingestion. Meanwhile, ClpV is a core secreted protein of the bacterial type VI secretion system (T6SS). Because elucidating ClpV's role in the pathogenesis of T6SS is pivotal for revealing the virulence mechanism of Salmonella, in our study, clpV gene deletion mutants were constructed using a λ-red-based recombination system, and the effect of clpV mutation on SL1344's pathogenicity was examined in terms of stress resistance, motility, cytokine secretion, gut microbiota, and a BALB/c mouse model. Among the results, ClpV affected SL1344's motility and was also involved in cell invasion, adhesion, and intracellular survival in the MDBK cell model but did not affect invasion or intracellular survival in the RAW264.7 cell model. Moreover, clpV gene deletion significantly reduced the transcription levels of GBP2b, IFNB1, IL-6, NLRP3, NOS2, and TNF-α proinflammatory factor levels but significantly increased transcription levels of IL-4 and IL-10 anti-inflammatory factors. Last, ClpV appeared to closely relate to the pathogenicity of S. Typhimurium in vivo, which can change the gut environment and cause dysbiosis of gut microbiota. Our findings elucidate the functions of ClpV in S. Typhimurium and illustrating interactions between T6SS and gut microbiota help to clarify the mechanisms of the pathogenesis of foodborne diseases.

Background Mannheimia haemolytica (M. haemolytica) is the primary pathogen responsible for respiratory diseases in ruminants. As an opportunistic pathogen, it often co-infects with other bacteria and viruses, leading to severe pneumonia. In this study, a suspected M. haemolytica pathogen was isolated from the lungs of sheep on a farm in Luoyang that exhibited respiratory symptoms and died acutely. The species classification, biological characteristics, and genome sequence analysis of the pathogen were determined. Results Morphological observations, biochemical tests, and phylogenetic analysis confirmed that the isolate was closely related to serotype A1 M. haemolytica GCA-900474405.1. Furthermore, sequence comparison of the capsular gene region revealed that the bacterium belonged to serotype A5 M. haemolytica and was named MH-1. Antibiotic sensitivity tests showed that MH-1 was resistant to tetracycline, erythromycin, spectinomycin and penicillin-G, and sensitive to other selected antibiotics. In animal experiments conducted on mice via intraperitoneal inoculation with MH-1, depression symptoms and dishevelled hair were observed in all mice in the highest-dose group, leading to death. The LD50 value for mice was determined to be 1.27×109 CFU. Whole-genome sequence analysis revealed that MH-1 had a total of 20 open reading frames (ORFs) encoded genes related to pathogenicity, including proteins involved in adhesion, invasion, iron uptake, and antiphagocytosis. While 8 ORFs were responsible for drug resistance genes, such as the macrolide resistance gene macB, the tetracycline resistance gene tet(35), the aminoglycoside resistance gene APH(3')-Ia, and the β-lactam resistance gene CRP. These findings were consistent with the results obtained from the antibiotic susceptibility test. Conclusion In conclusion, we successfully isolated and identified a strain of M. haemolytica serotype A5 from sheep. Through whole-genome sequencing and biological characterization analysis, we have enriched the understanding of the pathogenic properties of M. haemolytica in sheep. This information provides valuable insights for prevention and treatment strategies against M. haemolytica infections in sheep.

Ochratoxin A (OTA) is a significant global contaminant that poses severe challenges to food safety and public health. This study aims to isolate the OTA-degrated probiotics and evaluate genetic and biological characteristic. Here, The degradation rate of a new strain named Bacillus velezensis MM35 isolated from soil was the highest (87.10% within 48 h), and its culture supernatant was the main component of OTA degradation (63.95%) by high performance liquid chromatography. Further investigation revealed that the extracellular enzyme that degrades OTA in the culture supernatant of MM35 may be a small molecule enzyme with certain heat resistance. Genome-wide analysis showed that MM35 contains a cluster of carboxypeptidases encoding OTA-degrading potential, and had good metabolic and catalytic synthesis ability, and strong application potential in the synthesis and degradation of carbohydrates and proteins. A variety of secondary metabolites with antibacterial properties, such as non-ribosomal peptide synthetase and terpenoids, were identified in its metabolites. Consistent with the predicted results, MM35 showed various enzyme production characteristics such as cellulase and xylanase. Furthermore, MM35 could inhibit the growth of a variety of pathogenic bacteria, and showed high co-aggregation ability to Escherichia coli and Salmonella typhimurium. In addition, MM35 has certain tolerance to harsh environments such as strong acid, bile salt, and high temperature. Additionally, the adhesion rate of MM35 was 5.4%, and the invasion rate was 2.1% in IPEC-J2 cells. In summary, the data suggest MM35 isolated strain has high OTA degradation efficiency, antibacterial activity and intestinal colonization, which provided a new way for the treatment of OTA contamination in food and feed industries.