Regulatory role of the RstB-RstA system in adhesion, biofilm production, motility, and hemolysis.

For infection, initial invasion of the host is of great importance, with adhesion playing a critical role. We previously demonstrated rstA and rstB are remarkably downregulated in Vibrio alginolyticus cultured under heavy metal and acidic stresses, with impaired adhesion, suggesting that rstA and rstB might be involved in adhesion regulation. The present study showed that rstA and rstB silencing resulted in impaired adhesion, biofilm production, motility, hemolysis, and virulence. Meanwhile, changes of temperature, starvation, and pH remarkably affected rstA and rstB expression. These findings indicated that (1) rstA and rstB are critical regulators of adhesion in V. alginolyticus; (2) rstA and rstB have remarkable effects on biofilm production, motility, hemolysis, and virulence in V. alginolyticus; (3) rstA and rstB modulate adhesion in response to environmental changes of temperature, pH, and starvation.

Identification of outer membrane proteins of Vibrio parahaemolyticus and Vibrio alginolyticus altered in response to γ-irradiation or long-term starvation.

Vibrio parahaemolyticus and Vibrio alginolyticus were subjected to γ-irradiation (0.5 kGy) or starvation by incubation for 8 months in seawater to study modifications in their outer membrane protein patterns. After treatment, outer membrane protein profiles of starved or γ-irradiated bacteria were found to be altered when analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Altered proteins were identified by mass spectrometry (MS and MS/MS) and analyses revealed that OmpU can be considered a starvation stress-induced protein. In addition, expression of OtnA, OmpW, OmpA and peptidoglycan-associated lipoprotein decreased to non-detectable levels in starved cells. Furthermore, MltA-interacting protein MipA appeared under γ-irradiation or starvation conditions. Thus, it can be considered to be a γ-irradiation, long-term starvation stress protein in some vibrios.

Alterations of outer membrane proteins and virulence genes expression in gamma-irradiated Vibrio parahaemolyticus and Vibrio alginolyticus.

Gamma-irradiation technology sterilizes microorganisms and thereby prevents decay and improves the safety and shelf stability of food products. In this study we treated the foodborne pathogens Vibrio parahaemolyticus and Vibrio alginolyticus with gamma-irradiation (0.5 kGy) to evaluate their adaptative response. Outer membrane protein patterns of irradiated bacteria were found altered when analyzed by sodium dodecyl sulphate polyacrylamide gel electrophoresis. These modifications were manifested by the appearance and/or disappearance of bands as well as in the expression level of certain proteins. In addition, we searched for the presence of eight Vibrio cholerae virulence genes, toxR, toxS, toxRS, ctxA, zot, ace, toxT, and virulence pathogenicity island (VPI), in the genome of investigated strains. The expression of toxR, toxS, VPI, and ace genes in gamma-irradiated bacteria, studied by reverse transcriptase polymerase chain reaction, was altered. These variations were manifested by an increase and/or a decrease in the expression level of tested virulence genes.