QsvR and OpaR coordinately repress biofilm formation by Vibrio parahaemolyticus

Abstract

Mature biofilm formation by <i>Vibrio parahaemolyticus</i> requires exopolysaccharide (EPS), type IV pili, and capsular polysaccharide (CPS). Production of each is strictly regulated by various control pathways including quorum sensing (QS) and bis-(3'-5')-cyclic di-GMP (c-di-GMP). QsvR, an AraC-type regulator, integrates into the QS regulatory cascade <i>via</i> direct control of the transcription of the master QS regulators, AphA and OpaR. Deletion of <i>qsvR</i> in wild-type or <i>opaR</i> mutant backgrounds altered the biofilm formation by <i>V. parahaemolyticus</i>, suggesting that QsvR may coordinate with OpaR to control biofilm formation. Herein, we demonstrated both QsvR and OpaR repressed biofilm-associated phenotypes, c-di-GMP metabolism, and the formation of <i>V. parahaemolyticus</i> translucent (TR) colonies. QsvR restored the biofilm-associated phenotypic changes caused by <i>opaR</i> mutation, and vice versa. In addition, QsvR and OpaR worked coordinately to regulate the transcription of EPS-associated genes, type IV pili genes, CPS genes and c-di-GMP metabolism-related genes. These results demonstrated how QsvR works with the QS system to regulate biofilm formation by precisely controlling the transcription of multiple biofilm formation-associated genes in <i>V. parahaemolyticus</i>.