The CpxA/CpxR Two-Component System Affects Biofilm Formation and Virulence in Actinobacillus pleuropneumoniae

Abstract

Gram-negative bacteria have evolved numerous two-component systems (TCSs) to cope with external environmental changes. The CpxA/CpxR TCS consisting of the kinase CpxA and the regulator CpxR, is known to be involved in the biofilm formation and virulence of <i>Escherichia coli</i>. However, the role of CpxA/CpxR remained unclear in <i>Actinobacillus pleuropneumoniae</i>, a bacterial pathogen that can cause porcine contagious pleuropneumonia (PCP). In this report, we show that CpxA/CpxR contributes to the biofilm formation ability of <i>A. pleuropneumoniae</i>. Furthermore, we demonstrate that CpxA/CpxR plays an important role in the expression of several biofilm-related genes in <i>A. pleuropneumoniae</i>, such as <i>rpoE</i> and <i>pgaC</i>. Furthermore, The results of electrophoretic mobility shift assays (EMSAs) and DNase I footprinting analysis demonstrate that CpxR-P can regulate the expression of the <i>pgaABCD</i> operon through <i>rpoE</i>. In an experimental infection of mice, the animals infected with a <i>cpxA/cpxR</i> mutant exhibited delayed mortality and lower bacterial loads in the lung than those infected with the wildtype bacteria. In conclusion, these results indicate that the CpxA/CpxR TCS plays a contributing role in the biofilm formation and virulence of <i>A. pleuropneumoniae</i>.