The histidine kinase EnvZ regulates the swarming motility and biofilm formation of Vibrio parahaemolyticus

Abstract:

Objective Vibrio parahaemolyticus is a major foodborne pathogen that causes acute gastroenteritis in humans. Here, we aim to decipher the mechanisms by which the histidine kinase EnvZ regulates the swarming motility and biofilm formation of V. parahaemolyticus.Methods The plasmids pBAD24 and pMal carrying inducible promoters were used to construct the plasmids carrying target genes for overexpression. The recombinant plasmids were introduced into the wild-type strain (WT) and envZ-deleted strain (ΔenvZ) of V. parahaemolyticus. Swarming plates were prepared to measure swarming motility, while biofilm formation was detected by crystal violet staining. The RT-qPCR and bioluminescence reporter assays were employed to explore the mechanisms by which EnvZ regulated the expression of downstream genes.Results The swarming motility of ΔenvZ was significantly lower than that of WT, while the introduction of the pBAD24-envZ plasmid into ΔenvZ restored its swarming ability. The transcription levels of the lateral flagellar genes were positively correlated with the swarming motility. The promoter activities of P_scrABC-lux in ΔenvZ and ΔenvZΔompR were lower than those in WT and ΔompR. The swarming ability of ΔenvZ was significantly increased when the Scr system was overexpressed via the pMal-scrABC plasmid, while the overexpression of EnvZ in the strain without scrABC did not change the swarming motility. In addition, ΔenvZ exhibited a significant decrease in biofilm formation compared with WT. The pMal-envZ plasmid restored the biofilm formation of ΔenvZ to the level of WT, whereas the pMal-scrABC plasmid did not have this effect. The promoter activity of the extracellular polysaccharide operon (epsA-J) and the transcription levels of the extracellular polysaccharide genes in ΔenvZ were both significantly lower than those in WT.Conclusion The histidine kinase EnvZ enhances the swarming motility of V. parahaemolyticus by regulating the expression of the Scr system and promotes the biofilm formation by regulating the expression of extracellular polysaccharides.