GefC, a protein possessing a GGDEF domain, regulates biofilm formation, swimming motility, and pathogenesis in Vibrio parahaemolyticus.

Cyclic di-guanosine monophosphate (c-di-GMP), a bacterial second messenger, regulates diverse key processes including virulence, biofilm formation, and motility. Its synthesis involves diguanylate cyclases (DGCs) with GGDEF domains, while degradation is mediated by phosphodiesterases (PDEs) containing EAL or HD-GYP domains. This study examines the role of GefC (VP0486), a GGDEF domain protein in Vibrio parahaemolyticus, in c-di-GMP signaling, biofilm dynamics, motility, and virulence. Deletion of gefC markedly reduced cellular c-di-GMP, impaired biofilm formation, and reduced matrix components (exopolysaccharides, extracellular proteins, and extracellular DNA). Conversely, the ΔgefC mutant exhibited enhanced swimming motility and increased cytotoxicity and hemolytic activity, while zebrafish infection assays revealed attenuated lethality. Transcriptional analysis showed GefC differentially regulates EPS-related gene (cpsA), polar flagellar gene (flgM), type III secretion system 1 (vopN and vp1687), type VI secretion system 2 (hcp2, vpa1043, and vpa1044), and the TDH-encoding tdh2. Genetic evidence confirmed vp0485 and gefC form an operon. These findings establish GefC as a critical regulator of c-di-GMP-dependent biofilm development, motility, and virulence in V. parahaemolyticus, highlighting its multifaceted role in pathogenicity.