Functional studies of a type III and a novel secretion system of Edwardsiella tarda

Abstract

Edwardsiella tarda is an opportunistic gram-negative pathogen affecting both animals and humans. A type III secretion system (TTSS) and an EVP gene cluster contribute to E. tarda pathogenesis. EsrC, an AraC family protein, was under the control of a two-component system (EsrA-EsrB) and it in turn regulated selected genes in TTSS and the whole EVP gene cluster. Furthermore, a hypothetic protein (Orf2) of the TTSS affected the secretion but not the transcription of EseB and EseD. All the 15 EVP genes were systematically mutated and the results demonstrated that the EVP gene cluster encoded a novel secretion system. Thirteen EVP genes encoded for the putative apparatus and three proteins (EvpC, EssA and EvpI) were secreted through this system. Our research will benefit the understanding of E. tarda pathogenesis and provide new targets for the prevention and treatment of the infection diseases.