The GntR-like transcriptional regulator HutC involved in motility, biofilm-forming ability, and virulence in Vibrio parahaemolyticus

As a halophilic food-borne pathogen, Vibrio parahaemolyticus continueo be a major health issue worldwide. The pathogenic mechanisms of V. parahaemolyticus are still not fully understood. One of the most abundant and widely distributed groups of helix-turn-helix transcription factors is the GntR family of regulators, which are involved in the regulation of various biological processes in bacteria, but little is known about their functions in V. parahaemolyticus. Here, we identified a gene designated as hutC in V. parahaemolyticus SH112 that encodes a member belongs to the HutC subfamily of the large GntR transcriptional regulator family. Compared to the wild type, the hutC mutant strain was significantly more sensitive to acid, bile salt, Triton X-100, and sodium dodecyl sulfate stresses. Our results showed that HutC is required for optimal swimming motility but not necessary for the swarming of V. parahaemolyticus. In addition, inactivation of hutC in V. parahaemolyticus SH112 led to decreased biofilm formation, reduced cytotoxicity in Coca-2 cells, and defective virulence in vivo compared to the wild-type strain. Furthermore, transcriptome sequencing (RNA-Seq) analysis and real-time PCR indicated 4 upregulated and 14 downregulated genes in the hutC mutant strain. Functional analysis revealed that 4 upregulated genes were related to the histidine metabolism pathway. The 14 downregulated genes were mostly related to the cellular metabolic process, binding, and membrane part. This study presents evidence that HutC is involved in bacterial survival under conditions of stress, swimming motility, biofilm formation, cytotoxicity, virulence, and gene regulation of V. parahaemolyticus during infection.