LtrA is critical for biofilm formation and colonization of Vibrio parahaemolyticus on food-related surfaces.

Vibrio parahaemolyticus is the leading causative agent of seafood-associated acute gastroenteritis. The formation of biofilms is one of the key reasons for its resistance to adverse environments and its persistence in seafood. Investigating the regulatory mechanisms of biofilm formation is beneficial for the development of new intervention methods to reduce V. parahaemolyticus contamination during seafood processing and storage. In this study, we identified a global regulator, LtrA (VPA0519), which is involved in regulating biofilm formation in V. parahaemolyticus. The deletion of ltrA led to a significant alteration in the transcription levels of 706 genes, including those associated with type III and VI secretion systems and biofilm formation. LtrA positively regulated biofilm formation by enhancing the production of exopolysaccharides, extracellular proteins, extracellular DNA, and cyclic di-GMP (c-di-GMP), as well as by decreasing swimming and swarming motility. The deletion of the ltrA gene also led to a reduction in the metabolic activity of biofilm cells but did not affect the production of capsular polysaccharide. Furthermore, the deletion of the ltrA gene resulted in a decrease in the biofilm formation ability of V. parahaemolyticus on the surfaces of shrimp (Parapenaeopsis hardwickii), crab (Portunus trituberculatus), polypropylene plastic, glass, and stainless steel. The findings in this study extend our understanding of the roles of LtrA and the genetic determinants involved in biofilm formation by V. parahaemolyticus.