Objective: Vibrio parahaemolyticus causes acute gastroenteritis by secreting a number of virulence factors including two sets of type VI secretion systems (T6SS1 and T6SS2). However, it remains unknown how T6SS is regulated in the bacterium and what kinds of effects the systems have on adhesion onto and invasion into the host cells. This study was attempted to examine if VPA1045 and VPA1049 regulate T6SS2.
Methods: Vpa1045 and Vpa1049 deletion mutants were constructed by homologous recombination. Real-time PCR was performed to examine the transcription level of the translocon protein gene hcp2 in V. parahaemolyticus clinical strain HZ and its mutants. Western blot was used to analyze the levels of expression and translocation of Hcp2.
Results: Both VPA1045 and VPA1049 contain the Che-Y domain, and belong to the two-component regulators. Deletion of either Vpa1045 or Vpa1049 did not affect expression and transcription of Hcp2, but decreased translocation of Hcp2 in the supernatant of V. parahaemolycus. Bacterial adherence to the HeLa monolayers was also significantly reduced as compared with their parent strains.
Conclusion: The two-component regulators VPA1045 and VPA1049 regulate T6SS2 of V. parahaemolyticus post-translationally by up-regulating Hcp2 translocation.