Use of genetics and proteomics to study virulence factors of Edwardsiella Tarda

Abstract

Edwardsiella tarda is an important enteric pathogen. Its pathogenesis is largely unknown. Some of its virulence factors include the ability to invade non-phagocytic cells, survive in phagocytes and produce hemolysins and catalases. Comparative proteomics study of extracellular proteins of virulent and avirulent strains, revealed major virulent strain-specific proteins. Mass spectrometric analysis identified them to be homologous to the SseB, SseC and SseD proteins of the Salmonella pathogenicity island 2 type III secretion system (TTSS). Genome-walking showed the E. tarda cluster consists of more than 30 genes, including the apparatus, chaperones, effectors and regulators. Mutants with disrupted putative TTSS genes have reduced survival and replication in phagocyte and virulence. Regulation of the putative TTSS involves genes within and outside the cluster and is affected by temperature. The EseB, EseC and EseD proteins were deduced to form the translocon complex based on sequence homology and they were shown to interact by co-immunoprecipitation.