BfrR-mediated biofilm regulation in the seafood-borne pathogen Vibrio parahaemolyticus

Vibrio parahaemolyticus is a major seafood-associated pathogen whose biofilm formation enhances environmental persistence, antibiotic resistance, and food safety risks. In this study, we identified a LysR-type regulator, BfrR (VPA1687), as a critical mediator of biofilm development in V. parahaemolyticus. Deletion of bfrR severely impaired biofilm formation, switching colony morphology from wrinkled to smooth and reducing extracellular matrix components (exopolysaccharides (EPS), proteins, and extracellular DNA). BfrR also modulated metabolic activity in biofilm-embedded cells and exhibited dual control over motility: it inhibited swimming while promoting swarming. Mechanistically, BfrR elevated intracellular c-di-GMP levels by regulating genes encoding GGDEF/EAL domain proteins. RNA-seq revealed BfrR influences 500 genes, including biofilm-related pathways (e.g., cps operon for EPS), virulence factors, and flagellar genes. Critically, BfrR was essential for biofilm formation on diverse food-contact surfaces (shrimp, crab, stainless steel, plastic, and glass). These findings establish BfrR as a global regulator that coordinates biofilm formation, motility, and c-di-GMP signaling, highlighting its potential as a target for mitigating V. parahaemolyticus biofilm-associated risks in the food industry.