A two-component signal transduction system contributes to the virulence of Riemerella anatipestifer

Similar to other studies of bacterial pathogens, current studies of the pathogenesis of Riemerella anatipestifer (RA) are focused mainly on in vitro culture conditions. To elucidate further the pathogenesis of RA in vivo, bacterial RNA was extracted from overnight tryptic soy broth cultures (in vitro) and from the blood of infected ducks (in vivo) for comparative RNA sequencing analysis. In total, 682 upregulated genes were identified in vivo. Among the upregulated genes, a signal transduction response regulator (ArsR) and a signal transduction histidine kinase (SthK) were predicted to be located on the same operon. A mutant was constructed by deletion of both of these genes. Duck infection tests showed that genes ArsR and SthK were related to the virulence of the pathogen in vivo. Differentially expressed genes identified by comparison of in vitro and in vivo conditions provided an insight into the physiological process of RA infection and provided an opportunity to identify additional virulence factors.