Abstract
Motility is important for virulence, biofilm formation, and the environmental adaptation of many bacteria. Vibrio parahaemolyticus (V. parahaemolyticus) contains two flagellar systems that are responsible for motility, and are tightly regulated by transcription regulators and sigma factors. In this study, we identified a novel transcription factor, VPA1701, which regulates the swarming motility of V. parahaemolyticus. The VPA1701 deletion mutant (ΔVPA1701) eliminated the swarming motility on the surface of BHI agar plates and reduced colonization in infant rabbits. RNA-seq assays, confirmed by qRT-PCR, indicated that VPA1701 regulated the expression of lateral flagellar cluster genes. Further analyses revealed that VPA1701 directly binds to the promoter region of the flgBCDEFGHIJKL cluster to regulate the expression of lateral flagellar genes. CalR was originally identified as a repressor for the swarming motility of V. parahaemolyticus, and it was inhibited by calcium. In this study, we found that VPA1701 could inhibit the expression of the calR gene to increase the swarming motility of V. parahaemolyticus. Calcium downregulated the expression of calR, indicating that calcium could increase swarming motility of ΔVPA1701 by inhibiting calR. Thus, this study illustrates how the transcription factor VPA1701 regulates the expression of lateral flagellar genes and calR to control the swarming motility of V. parahaemolyticus.
Highlights
V. parahaemolyticus is a foodborne pathogen sometimes found in contaminated seafood, which can cause acute-gastroenteritis and hemorrhagic sepsis in humans [1,2]
The polar flagellum is encoded by the polar flagellar genes responsible for the swimming motility, and the lateral flagellum is responsible for the swarming motility encoded by lateral flagellar genes [11]
VPA1701 has been identified as a transcriptional regulatory protein in the GntR family that contains a conserved helix-turn-helix (HTH) for DNA binding at the N-terminus and an effector binding domain involved in oligomerization at the C-terminus [30]
Summary
V. parahaemolyticus is a foodborne pathogen sometimes found in contaminated seafood, which can cause acute-gastroenteritis and hemorrhagic sepsis in humans [1,2]. The major virulence factors of V. parahaemolyticus are hemolysin (thermostable direct hemolysin [TDH], TDH-related hemolysin [TRH]), type III secretion systems (T3SS1 and T3SS2), type VI secretion systems (T6SS1 and T6SS2), biofilm formation, motility, protease production and iron uptake system [3,4,5,6,7,8]. The pathogenesis processes of V. parahaemolyticus include motility, adhesion, invasion, proliferation, production of toxins in vivo, and the damage to cells and tissues [9,10]. Motility plays an essential role in the infection of V. parahaemolyticus in the host, and the protease production can benefit host invasion. The. V. parahaemolyticus contains two flagellar systems: polar flagellum and lateral flagellum.
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