Objective To perform biological characterization and genomic analysis for a multidrug-resistant Streptococcus strain isolated from the tonsils of a dead piglet, thus elucidating its phenotypic and genotypic characteristics. Methods The tonsillar tissue homogenate from the dead piglet was inoculated into the Streptococcus enrichment medium for enrichment culture. The enriched culture was then streaked onto Columbia blood agar medium for Streptococcus isolation. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), a biochemical identification system, and 16S rRNA gene sequencing were employed for strain identification. The minimum inhibitory concentrations (MICs) were determined by the broth microdilution method. Whole-genome sequencing was conducted via the Illumina platform. The ResFinder database was used to analyze the resistance genes, and mutations in the genes encoding penicillin-binding proteins (PBPs) were investigated through multiple sequence alignment. Results The phylogenetic analysis based on 16S rRNA gene sequences identified the isolate as Streptococcus orisratti. Antimicrobial susceptibility testing revealed that the strain was resistant to penicillin G, erythromycin, clindamycin, and compound sulfamethoxazole, and it exhibited reduced susceptibility to linezolid. Whole-genome analysis identified the presence of the macrolide and lincoamide resistance gene ermB and the oxazolidinone resistance gene optrA. Furthermore, multiple mutations were detected in the genes encoding PBPs. Conclusion This study reports the first isolate of S. orisratti harboring both ermB and optrA and exhibiting resistance to penicillin. It highlights the capacity of porcine-derived streptococcal strains to acquire multidrug resistance genes, underscoring the need for increased vigilance regarding the resistance traits and transmission risks of animal-derived streptococci.

Objective To screen indigenous rhizobia with high salt tolerance and plant growth-promoting traits from alfalfa nodules and clarify their phylogenetic status and functional potential, thereby providing strain resources and a theoretical basis for developing localized, efficient alfalfa symbiosis and further addressing the constraints of saline soil on alfalfa production in Inner Mongolia. Methods Indigenous alfalfa rhizobia were collected from six saline-alkali sites in Inner Mongolia via a trapping method. Following isolation and purification, the taxonomic status of the strains was determined by 16S rRNA gene sequencing. The plant growth-promoting functions were evaluated through nodulation tests, along with assays for nitrogen fixation, phosphorus solubilization, potassium solubilization, indole-3-acetic acid (IAA) production, and exopolysaccharide (EPS) content. Seed germination and pot experiments were carried out to evaluate the salt stress-alleviating effect of the target strain. Results A total of 250 strains were isolated, with Sinorhizobium meliloti being predominant (227 strains, 90.8%). Eight efficient nodulating strains (e.g., 1B1Y and 1B2Y) were screened out, all of which possessed nitrogen-fixing and potassium-solubilizing capabilities. Some strains (e.g., 2B3Y and 9B3Y) could solubilize organic phosphorus and produce siderophores. Strain 9B3Y secreted the highest amount of IAA (67.5 mg/L), while 16C1Y produced the highest EPS content (2.684 g/L). Under salt stress (0.4% NaCl), the aboveground fresh weight of alfalfa inoculated with strain 2B3Y increased by 29% compared with that of the saline control, and the strain significantly alleviated the inhibition on seed germination (notably increasing the root length). Conclusion The strains screened out, particularly strain 2B3Y, can effectively mitigate the inhibitory effects of salt stress on alfalfa through nitrogen fixation and the secretion of IAA and EPS. These strains show promise for application in alfalfa production and soil improvement in saline regions of Inner Mongolia.

Uropathogenic Escherichia coli (UPEC) is the leading cause of urinary tract infections (UTIs). It can adhere to and colonize uroepithelial cells, disseminate systemically, and induce severe sepsis and subsequent renal failure, posing a substantial threat to global public health. Emerging evidence indicates that lactylation, a key post-translational modification (PTM) in macrophages, plays a crucial role in the host defense against UPEC infection. Notably, the UPEC CFT073 strain harbors ldhA, which encodes lactate dehydrogenase (LDH), an enzyme critical for lactate biosynthesis. However, the mechanism by which LdhA (the ldhA-encoded LDH) regulates macrophage lactylation during UPEC infection remains elusive. Objective To elucidate how LdhA modulates macrophage lactylation and thereby impacts UPEC pathogenicity. Methods Online bioinformatics tools were used to predict the functional domains and transmembrane regions of LdhA. The recombinant protein rLdhA was generated via molecular cloning, and its LDH activity was measured by a commercial LDH activity assay kit. Western blotting was performed to assess the cellular entry of rLdhA into macrophages and its regulatory effect on macrophage lactylation. Enzyme-linked immunosorbent assay (ELISA) was employed to measure the secretion of inflammatory cytokines in macrophages treated with rLdhA. The drug resistance profile of UPEC CFT073 (wild-type and ldhA-knockout strains) was analyzed via an automated microbial identification system. To evaluate the role of LdhA in UPEC pathogenicity, we treated mice with the wild-type UPEC CFT073 (CFT073^wt), ldhA-deficient mutant (CFT073^ΔldhA ), or rLdhA (with or without pretreatment with an LDH inhibitor) through intraperitoneal injection or tail vein injection, and then observed and quantified pathogenic phenotypes. Results LdhA harbored a LDH domain and was secreted extracellularly. We successfully established an expression system for ldhA and achieved efficient expression and purification of rLdhA. Functional assays confirmed that rLdhA exhibited LDH activity and can enter macrophages via clathrin-mediated endocytosis, subsequently enhancing macrophage lactylation in a dose-dependent manner. Additionally, rLdhA significantly inhibited lipopolysaccharide (LPS)-induced inflammatory cytokine production in macrophages. Furthermore, LdhA was found to substantially modulate the drug resistance profile of UPEC CFT073. In vivo studies demonstrated that LdhA promoted the pathogenicity of UPEC in a mouse infection model. Conclusion Collectively, our findings demonstrate that LdhA enhances UPEC pathogenicity by upregulating macrophage lactylation and suppressing the production of proinflammatory cytokines. However, the underlying molecular mechanisms mediating this regulatory cascade remain to be fully elucidated and warrant further exploration. This study offers a new theoretical basis for deciphering the pathogenic mechanisms of UPEC infections.

Objective Senecavirus A (SVA) keeps posing a serious threat to the swine industry in China. This study aimed to characterize the biological properties and genetic evolutionary features of the latest circulating SVA strains. Methods In November 2024, vesicular lesion tissue samples were collected from pigs suspected of foot-and-mouth disease at a farm in eastern China. RT-PCR was performed, and positive samples were inoculated onto BHK-21 cells following standard virus isolation procedures. Indirect immunofluorescence assay was employed to preliminarily confirm viral isolation. The complete viral genome was amplified and sequenced, followed by genetic evolution analysis. Amino acid variations in the VP1 protein of the strain were identified by comparison with representative strains from key epidemic nodes. Viral replication characteristics were evaluated through plaque formation assay and one-step growth curve analysis. Viral particle morphology was observed via transmission electron microscopy (TEM). Results RT-PCR and virus isolation confirmed SVA as the causative agent of the disease, and the isolated strain was designated SDWF/11/2024. The viral genome of this strain was 7 292 bp in length, and its overall organization was highly consistent with that of previously reported SVA strains. Phylogenetic analysis revealed that SDWF/11/2024 belonged to the USA-like evolutionary clade, showing genetic divergence from Chinese strains circulating between 2015 and 2018, while exhibiting the closest relationship to a Chilean strain isolated in 2022. The isolate replicated efficiently in BHK-21 cells and induced typical cytopathic effects. Its replication kinetics was comparable to that of the early Chinese isolate HN/11/2017, although differences in plaque morphology were observed. TEM examination identified spherical viral particles with diameters of 25-35 nm, consistent with typical SVA virions. Conclusion This study successfully isolated and characterized the SVA strain SDWF/11/2024 circulating in China, 2024, and elucidated its molecular evolutionary features. The isolated SDWF/11/2024 provides a new reference strain for SVA surveillance in China and suggests that the virus may still persist at low levels in pig populations. These findings enhance our understanding about the genetic diversity and epidemic dynamics of SVA and support the improvement of molecular epidemiological monitoring and the development of prevention and control strategies.

Heat shock protein family A member 8 (HSPA8) is a widely distributed molecular chaperone in cells. HSPA8 is involved in multiple cellular physiological processes, mainly including the correct folding and transport of proteins, stress responses, presentation of antigenic proteins, mediation of autophagy, and immune regulation. It is also crucial for maintaining the homeostasis of the intracellular environment. In addition, HSPA8 plays a key role in multiple processes of virus infections. This paper reviewed the important roles and molecular mechanisms of HSPA8 in processes such as virus adhesion, formation of virus glycoprotein-receptor complexes, internalization, uncoating, genome replication, assembly, and regulation of host metabolism and immune responses, with the hope of laying a foundation for the subsequent development of drugs targeting HSPA8 for the treatment of virus infections.

Coronaviruses pose a serious threat to human and animal health. Their main protease (Mpro) plays a critical role in both the viral life cycle and host immune regulation, serving as a key target for the development of broad-spectrum anti-coronavirus drugs. The core function of Mpro lies in its specific cleavage of viral polyproteins pp1a and pp1ab to release functional non-structural proteins (NSPs), thereby driving the assembly of the viral replication/transcription complex. Additionally, Mpro can target and cleave key molecules in host immune signaling pathways, facilitating viral immune evasion. Given its dual roles and highly conserved catalytic center, the research on Mpro has become a major focus in the field. This review systematically outlines the structural features and functional diversity of Mpro, with an emphasis on its catalytic mechanism in the viral replication cycle and its role in mediating immune suppression. Furthermore, this article details the screening methods and design strategies for Mpro inhibitors, aiming to offer theoretical foundations and novel insights for the development of anti-coronavirus drugs targeting this critical protein.

Pasteurella multocida (Pm) and Mannheimia haemolytica (Mh) are major bacterial pathogens responsible for bovine respiratory diseases. However, the diversity of these two pathogens in transported calf populations remains poorly understood, which severely hinders the effective prevention and control of their infections. Objective To investigate the diversity of Pm and Mh in a group of fattening calves purchased from a calf trading market in Inner Mongolia and transported to a breeding farm in Hechuan, Chongqing. Methods After arrival, nasal swabs were collected from calves showing respiratory symptoms at four time points for bacterial isolation and culture. Suspected Pm and Mh colonies were selected based on colony morphology, hemolytic characteristics, and Wright-Giemsa staining results, followed by PCR identification and 16S rRNA gene sequencing for confirmation. Furthermore, the serotypes, biochemical and antibiotic resistance profiles, virulence genes, and resistance genes of the isolates were analyzed. Results A total of 23 strains of Pm serotype A, 10 strains of Mhserotype A6, and 1 strain of Mhserotype A2 were isolated from 68 nasal swabs collected at 4 different time points, and only 1 nasal swab harbored both Pm and Mh. Some isolates exhibited diversity in biochemical and antibiotic resistance profiles, which had no significant correlation with sampling time points. Antimicrobial susceptibility testing revealed that Pm and Mh isolates were resistant to most penicillins, aminoglycosides, and lincosamides but remained sensitive to cephalosporins and quinolones. Resistance gene detection showed that β-lactamase resistance (bla_TEM ) genes were detected in 73.91% of Pm isolates and 90.91% of Mh isolates, while sulfonamide resistance (sul2) genes were found in 69.57% of Pm isolates and 18.18% of Mh isolates. Only one Mh isolate carried aminoglycoside resistance genes (aadA25 and aadB). Discrepancies were observed between resistance phenotype and the presence of selected resistance genes. All Pm and Mh isolates were pathogenic. Virulence gene analysis confirmed that Pm isolates consistently carried tonB, hsf-1, nanB, oma87, and tbpA, while Mh isolates showed the detection rates of 100% for gapA and dnaN, 82% for lktA, plpB, and tbpB, and 0 for ptfA. Conclusion These findings suggest that calves purchased from trading markets and transported over long distances to new farms harbor Pm and Mh strains exhibiting diversity in biochemical characteristics and drug resistance, which pose challenges for effective infection control. This study provides critical insights for developing prevention and control strategies against Pm and Mh infections in transported calves.

Objective To construct high-yield engineering strains of Halomonas campaniensis XH26 by introducing five recombinant plasmids (pHX01-pHX05), each carrying the P _tac promoter and combinations of the genes asd, lysC, ectA, ectB, and ectC. This metabolic engineering strategy was coupled with the response surface methodology (RSM) for optimization of the culture conditions, thereby enhancing ectoine accumulation. Methods The recombinant plasmids were conjugally transferred from Escherichia coli S17-1(λ-pir) into H. campaniensis XH26, with positive transconjugants selected via gentamicin (50 μg/mL). Recombinant strains were induced with 0.2 mmol/L IPTG, and ectoine accumulation was quantified by HPLC. Critical nutritional variables—NaCl, peptone, l-glutamate, and glucose—were optimized through one-factor-at-a-time experiments, Plackett-Burman design, and Box-Behnken design. Results Five recombinant strains (XH26/pHX01-XH26/pHX05) were successfully constructed. Culture in the MG medium revealed that strain XH26/pHX04 (overexpressing asd-lysC-ectA-ectB) achieved the highest ectoine titer of (1.32±0.04) g/L. Strains XH26/pHX05 and XH26/pHX03 achieved the ectoine titer of (1.19±0.07) g/L and (1.07±0.08) g/L, respectively, while XH26/pHX02 yielded a lower titer of (1.02±0.14) g/L. The medium composition optimized by RSM was composed of 116.08 g/L NaCl, 16.30 g/L peptone, 169.57 g/L l-glutamate, and 15.53 g/L glucose. Under these optimized conditions, the titer of ectoine produced by XH26/pHX04 increased to (1.81±0.02) g/L, representing a significant increase of 301.56% compared with that of the wild-type strain XH26. Conclusion This study demonstrates that using H. campaniensis as a chassis and overexpressing a key gene combination (asd, lysC, ectA, ectB) under a strong promoter, synergized with culture medium optimization via RSM, can significantly boost the ectoine yield of recombinant strains. The findings provide a robust technical framework for the subsequent industrial production of ectoine.

Understanding the source, colonization rules, and dynamic evolution process of the gut microbiota is of significant importance for regulating host health, given its crucial role in nutrient metabolism, immune regulation, and intestinal barrier function. This article comprehensively reviews the composition and functions of the gut microbiota and explores the origins and transmission pathways, with a particular focus on the effects of maternal-infant transmission and paternal inheritance on the structure and functions of the gut microbiota. We chart microbial assembly across pivotal life stages, distill the driving factors involved in the community assembly process, and critically appraise the advances in metagenomic and source-tracking toolkits. The review provides an integrated framework for microbiome-targeted strategies aimed at reconstructing a health-oriented gut ecosystem.

Objective Mixotrophy that combines phototrophic autotrophy and phagotrophic heterotrophy is widespread among unicellular eukaryotic microalgae and plays a key ecological role in energy flow within food webs and in elemental biogeochemical cycles. However, identifying and characterizing mixotrophic microalgae in natural waters remains technically challenging. Improving current approaches to accurately reveal the diversity of mixotrophic microalgae is an urgent task in this field. Methods Fluorescently labeled prey surrogates and feeding experiments were employed to trace phagotrophic microalgae within plankton communities. Target organisms were captured at the single-cell level through fluorescence-activated cell sorting (FACS), followed by multiple-displacement amplification (MDA) and 18S rRNA gene sequencing for taxonomic identification. On the basis of this FACS-MDA workflow, we established a methodological framework for studying the functional groups of microalgae. Results Applying this approach to multiple freshwater and seawater samples from China, we identified twenty phagotrophic microalgal species belonging to six classes and twelve genera, as well as heterotrophic consumers representing one class and three genera, demonstrating the robustness and broad applicability of this method. Conclusion This study applies the combined FACS-MDA technology to the identification of functional groups of microalgae in natural water bodies. The established technology has broad application prospects in microbial ecology. It enables deeper insights into the functional diversity and in situ feeding activities of environmental microalgae.