Connecting type VI secretion, quorum sensing, and c-di-GMP production in fish pathogen Vibrio alginolyticus through phosphatase PppA

Vet Microbiol. 2013 Mar 23;162(2-4):652-662. doi: 10.1016/j.vetmic.2012.09.009. Epub 2012 Sep 14.


Vibrio alginolyticus, a Gram-negative marine bacterium, has brought about severe economic damage to the mariculture industry by causing vibriosis in various fish species. We are intrigued in the regulation of the pathogenesis in this bacterium. Here, we reported a complex regulatory connection among the newly defined type VI secretion system (T6SS), quorum sensing (QS), and 3',5'-cyclic diguanylic acid (c-di-GMP) signal through the phosphatase PppA encoded in the T6SS gene cluster of V. alginolyticus. Whole-genome transcriptome analysis revealed various regulatory targets of PppA including the T6SS substrate hemolysin coregulated protein (Hcp), quorum sensing regulator LuxR, exotoxin alkaline serine protease (Asp), flagellar proteins, as well as proteins involved in polysaccharide biosynthesis and transport. Western blot analysis showed PppA served as a negative regulator of the expression and secretion of Hcp1. Mutation of pppA resulted in an increased level of the intracellular second messenger c-di-GMP and a decreased expression of the QS regulator LuxR as well as exotoxin Asp. Complementation of intact pppA gene in ΔpppA mutant restored the production of c-di-GMP, LuxR, and Asp to the wild-type level. Phenotypic studies suggested that PppA takes part in the modulation of biofilm formation, motility, and cell aggregation. These results demonstrated new roles of PppA in controlling virulence factors and pleiotropic phenotypes and contributed to our understanding of the regulation of pathogenesis in V. alginolyticus.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Bacterial Secretion Systems / genetics
  • Bacterial Secretion Systems / physiology*
  • Cyclic GMP / analogs & derivatives*
  • Cyclic GMP / biosynthesis
  • Endopeptidases / genetics
  • Endopeptidases / metabolism
  • Fishes
  • Gene Expression Regulation, Bacterial
  • Hemolysin Proteins / genetics
  • Hemolysin Proteins / metabolism
  • Phosphoprotein Phosphatases / genetics
  • Phosphoprotein Phosphatases / metabolism*
  • Quorum Sensing / physiology*
  • Serine Endopeptidases / genetics
  • Serine Endopeptidases / metabolism
  • Vibrio Infections / microbiology
  • Vibrio Infections / veterinary*
  • Vibrio alginolyticus / enzymology
  • Vibrio alginolyticus / genetics
  • Vibrio alginolyticus / physiology*
  • Virulence Factors / genetics
  • Virulence Factors / metabolism


  • Bacterial Proteins
  • Bacterial Secretion Systems
  • Hemolysin Proteins
  • Virulence Factors
  • bis(3',5')-cyclic diguanylic acid
  • Phosphoprotein Phosphatases
  • Endopeptidases
  • Serine Endopeptidases
  • alkaline protease
  • Cyclic GMP