Regulation mechanism of virulence by environmental acidic stress mediated by Prc in Edwardsiella piscicida

Abstract

Edwardsiella piscicida is a conditional pathogen that causes devastating infections in numerous fish species, leading to huge economic losses in the aquaculture industry. The E. piscicida pathogenicity is majorly attributable to its type III and VI secretion systems (T3/T6SSs) that are regulated by a two-component system (TCS) EsrA-EsrB. In this study, we illustrated that a PDZ-domain-containing protease (Prc) regulated the expression of esrB and T3/T6SSs in different manners at different growth stages. Furthermore, Prc mediated the regulation of environmental acidic signals on the expression of esrB. Mutation of esrA impaired E. piscicida virulence expression irrespective of the ambient acidic signals. Collectively, Prc could react with the activated EsrA and influence the expression of esrB and T3/T6SSs. These findings reveal an extensive understanding of the virulence regulation upon sensing the environmental acidic signals in bacterial pathogens.