Abstract:[Objective] Vibrio parahaemolyticus is a significant foodborne pathogen that causes economic and public health problems worldwide. In this study, we explored the roles of the two-component system (TCS) EnvZ/OmpR in mediating the alkaline stress tolerance of V.parahaemolyticus.[Methods] We identified the two-component system EnvZ/OmpR in the V.parahaemolyticus chromosomes with SMART (https://smart.embl.de/). Then, we constructed the envZ-deleted strain, the ompR-deleted strain, as well as the complemented strains. On this basis, we compared the alkaline stress tolerance of the wild-type strain and the mutants, and the mechanisms whereby the EnvZ/OmpR regulated the alkaline stress tolerance of V.parahaemolyticus were explored by qRT-PCR and bioluminescence reporter assay. [Results] Homology analysis of the VP0155 and VP0154 proteins revealed that their amino acid sequences shared a high identity with the two-component system EnvZ/OmpR. ompR deletion decreased the tolerance of V.parahaemolyticus to osmotic stress and alkaline stress, while the growth status of C△ompR, △envZ, and C△envZ was similar to that of the wild type. The transcription levels of porin genes vp1218, vp0493, vpa1745, vpa0085, and vpa1308 in △ompR were lower than those in the wild type, and the deletion strains of the porin genes (except for △vpa1308) showed low growth ability in the alkaline-shock environment as compared with the wild strains. In addition, OmpR inhibited the expression of AphB and △aphB was significantly more tolerant to alkaline stress than the wild type. Moreover, AphB can directly repress the transcription of vp0493 and vpa0085. [Conclusion] The two-component system EnvZ/OmpR mediates alkaline stress tolerance of V. parahaemolyticus, which depends on the transcriptional factor AphB to regulate the expression of the porins.
