Abstract:Edwardsiella tarda (E. tarda) could exist and replicate in vivo and in vitro such as in macrophage. The eha gene is an important regulating gene in E. tarda. We explored its role and mechanism for E. tarda to resist to macrophage stresses in this study. We compared the survival rates of ET-13 virulence strains with their eha mutant strains (Δeha) and complementary strains (ehaComp) by a series of stress experiments in vitro, which were imitated oxidation and acid condition in macrophage, serum and bile condition in vivo. Compared with the wilds, the survival rates of eha mutant strains decreased significantly (P<0.05) in the conditions of acid, H2O2, SDS, and polymyxin B. There’s no significant difference (P>0.05) between the survival rates of eha mutants and ones of the wild strains with the treatment of mice serum or fish bile. The transcription level of the genes of superoxide dismutase C (sod C), catalase B (katB), flagellin C (fliC), and secretary protein C (eseC) of III type secretary system protein in the mutants were lower by RT-PCR. The expression of main outer membranes in the mutants was decreased by SDS-PAGE electrophoresis. The results showed that the eha gene may control some related virulence factors for E. tarda to resist acid and oxidants to kill in macrophage. The eha gene was helpful for E. tarda to replicate in macrophage.
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