FlhF interacts with TonB2 to defend against oxidative stress in Campylobacter jejuni.

Multi-omics reveals an extracellular vesicles-mediated susceptibility: Conferring carbenicillin resistance while compromising copper tolerance in Vibrio parahaemolyticus.

Extracellular vesicles (EVs) serve as pivotal mediators of bacterial intercellular communication, facilitating survival under diverse environmental hostilities. However, the regulatory landscape of EVs under the complex interplay of antibiotic and heavy metal co-stress remains an enigma. Here, we integrated multi-omics analyses to decipher the impact of EVs derived from a multidrug-resistant Vibrio parahaemolyticus strain (VP38) on a susceptible strain (VP35) under separated or combined stress of carbenicillin (CARB) and copper (Cu). Unexpectedly, the EV-mediated effects were stress-type specific: they promoted survival under CARB stress but markedly reduced viability under Cu exposure. Mechanistically, transcriptomic analysis showed that EVs uptake was associated with transcriptional reprogramming in the recipient strain, including downregulation of copper efflux genes (e.g., cusB/R) and iron acquisition genes (e.g., TonB-dependent receptors). This expression pattern suggests a possible disturbance in intracellular ion homeostasis and may contribute to increased susceptibility to heavy metal stress. These findings support a context-dependent defense-burden model of EV-mediated stress adaptation under combined antibiotic and metal stress. This study not only advances our understanding of bacterial social behaviors but also highlights EV-induced metabolic interference as a potential therapeutic strategy against resistant pathogens in aquaculture.

Taxifolin impairs colonization of Clostridium perfringens in association with iron limitation-related physiological stress

Findings support a working model in which iron limitation-associated physiological stress contributes to the inhibitory effects of taxifolin on C. perfringens growth and colonization-related phenotypes and support its potential use as a plant-derived approach for limiting C. perfringens intestinal colonization.

is required for an effective

LtrB inhibits Vibrio parahaemolyticus motility while promoting biofilm formation and seafood adhesion

Vibrio parahaemolyticus is a major seafood-borne pathogen whose ability to form biofilms enhances its persistence in food-processing environments and contributes to its resistance to antimicrobial agents. In this study, we investigated the role of the LysR-type transcriptional regulator LtrB (VPA0388) in coordinating the switch between motility and biofilm formation in V. parahaemolyticus. We demonstrated that LtrB is required for proper biofilm development, extracellular matrix production, and wrinkled colony morphotype formation, while simultaneously repressing both swimming and swarming motility. Mechanistically, we showed that LtrB acts as a direct transcriptional regulator that binds to the promoter regions of multiple genes, including biofilm-matrix genes (cpsA, scvE, cpsQ, mfpA) and flagellar genes (flgM, flgA, flgB, flgK, lafA, fliD), activating the former and repressing the latter. In contrast, the regulation of motY and fliM appears to be indirect, as no binding of LtrB to their promoter regions was detected. Furthermore, LtrB exerts these regulatory effects largely independently of the c-di-GMP signaling pathway, as intracellular c-di-GMP levels remain unaltered upon ltrB deletion. Consistent with its role in promoting a sessile lifestyle, LtrB was required for bacterial adhesion to biotic (mussel and shrimp) and abiotic (glass and stainless steel) surfaces relevant to food production. These findings establish LtrB as a regulator that promotes a sessile, biofilm-forming lifestyle by downregulating motility and upregulating matrix production, thereby facilitating persistent colonization in food-related environments.

ArlR regulates environmental stress tolerance and biofilm formation in foodborne Staphylococcusaureus

Staphylococcus aureus (S. aureus) is a major Gram-positive pathogen capable of sensing and responding to diverse host- and environment-derived stresses, contributing to both clinical infections and foodborne illnesses. This exceptional stress tolerance is primarily mediated by intricate regulatory networks. Although the ArlRS two-component system is known to regulate autolysis, capsule synthesis, and virulence, the specific role of ArlR in environmental stress adaptation remains poorly understood. In this study, we demonstrate that deletion of arlR significantly reduces the tolerance of the foodborne strain RMSA49 to acetic acid, desiccation, whereas its responses to temperature and osmotic stress not affected. Notably, the arlR mutant also exhibits significantly enhanced biofilm formation. Transcriptomic analysis, validated by RT–qPCR, further reveals that ArlR regulates a broad set of stress- and biofilms-associated genes, highlighting its central role in coordinating environmental adaptation. These findings establish ArlR as a key regulator of environmental stress adaptation in foodborne S. aureus RMSA49 and suggest its potential as a target for controlling S. aureus.

Pleiotropic roles of the MATE transporter CD20030 in Clostridioides difficile: linking multidrug resistance to oxidative stress defense and virulence regulation

Background The multidrug-resistant pathogen Clostridioides difficile (C. difficile) presents a persistent clinical threat. While Multidrug and Toxic Compound Extrusion (MATE) transporters are recognized as xenobiotic efflux pumps, their pleiotropic roles in pathogen physiology, particularly in stress adaptation and virulence regulation, remain largely unexplored. Understanding how C. difficile adapts and thrives in the face of host defenses and antimicrobial pressures, potentially influencing gut microbiome dynamics, is crucial for combating C. difficile infection. Methods We functionally characterized the MATE transporter gene CD20030 (mate) in C. difficile 630. A markerless deletion mutant (Δmate) and a complemented strain were constructed using a CRISPR-Cas9 system. Phenotypic assays determining antimicrobial susceptibility, oxidative stress tolerance, autolysis, and cytotoxicity were integrated with comparative proteomic profiling to assess the physiological changes. Results The Δmate mutant demonstrated broad-spectrum hypersensitivity to antibiotics and hydrogen peroxide, indicating the involvement of this transporter in intrinsic resistance and oxidative defense. The mutant exhibited reduced autolysis; however, toxin production (tcdA and tcdB) and cytotoxicity were significantly upregulated. In soft agar assays, the mutant showed expanded surface spreading. Proteomic data identified a >10,000-fold downregulation of flagellar structural proteins (FliC, FlgC) and a concurrent upregulation of the surface adhesin CwpV. This molecular evidence indicates a “swimming-to-sliding transition” driven by metabolic stress, rather than active swimming motility. These phenotypic and proteomic shifts present a resource reallocation strategy, where the bacterium sacrifices energy-consuming flagellar assembly to prioritize survival and virulence, potentially altering its interaction with the gut epithelial surface and resident microbiota. Conclusion The MATE transporter (CD20030) operates as a pleiotropic regulatory hub and metabolic sentinel in C. difficile. Its absence induces metabolic reprogramming that orchestrates a motility-virulence trade-off, linking multidrug resistance directly to bacterial pathogenesis. These physiological adaptations likely dictate the pathogen′s colonization and persistence strategies within the gut niche, potentially perturbing the host-microbiome equilibrium during infection.