GefB, a GGDEF domain-containing protein, affects motility and biofilm formation of Vibrio parahaemolyticus and is regulated by quorum sensing regulators

Vibrio parahaemolyticus (V. parahaemolyticus) stands as the predominant etiological agent responsible for gastroenteritis associated with the consumption of seafood. Cyclic di-guanosine monophosphate (c-di-GMP), a secondary messenger in bacteria, controls multiple bacterial behaviors including pathogenesis, the development of biofilms, and motility. The protein GefB (VPA1478), characterized by the presence of a GGDEF domain, inhibits the swarming motility of V. parahaemolyticus. In this study, we showed that deletion of gefB remarkably reduced cellular c-di-GMP level and biofilm formation by V. parahaemolyticus, but significantly enhanced the swimming and swarming motility. In addition, GefB inhibited the polar and lateral flagellar genes but activated genes associated with exopolysaccharide production of V. parahaemolyticus. The data also demonstrated that vpa1477 and gefB are co-transcribed as a single transcriptional unit, designated as vpa1477-gefB. Transcription of vpa1477-gefB was under the collective regulation of the master quorum sensing (QS) regulators AphA and OpaR, which function at low (LCD) and high cell density (HCD), respectively. AphA positively regulated vpa1477-gefB transcription at LCD, whereas OpaR negatively regulated its transcription at HCD. The findings significantly enhance our comprehension of the metabolism and regulatory mechanisms of c-di-GMP in V. parahaemolyticus.