TCS response regulator OmpR plays a major role in stress resistance, antibiotic resistance, motility, and virulence in Edwardsiella piscicida

Abstract

Two-component regulatory systems (TCSs) are omnipresent in Gram-negative bacteria and play a major role in response to changes in environmental cues and pathogenicity. Edwardsiella piscicida is a serious pathogen of fresh and seawater aquaculture industries and has attracted increasing attention. However, extremely limited TCSs have been reported in E. piscicida. In this study, the role of response regulator OmpR which belongs to TCS EnvZ/OmpR was investigated in E. piscicida. By construction of a markerless ompR in-frame mutant strain, TX01ΔompR, we found that (i) in comparison to the wild type TX01, TX01ΔompR exhibited markedly compromised tolerance to acid stress, osmotic stress, and oxidative stress; (ii) the deletion of ompR significantly changed bacterial sensitivity to multiple antibiotics, (iii) the deficiency of ompR tremendously reduced bacterial motility, (iv) the deficiency of ompR abated bacterial colonization in host immune tissue and bacterial overall virulence. These results indicate OmpR is an important participant in E. piscicida's adversity resistance and pathogenicity. As a response regulator, OmpR was demonstrated to downregulate acid resistance system cadBA and to upregulate the porin ompC and flagellum mediator flhDC. Taken together, our results illustrate that OmpR is a vital regulator that coordinates the expressions of multiple genes during the response to an adverse environment and invasion to host.