The roles of cell wall inhibition responsive protein CwrA in the pathogenicity of <i>Staphylococcus aureus</i>

The ability to form robust biofilms and secrete a diverse array of virulence factors are key pathogenic determinants of <i>Staphylococcus aureus</i>, causing a wide range of infectious diseases. Here, we characterized <i>cwrA</i> as a VraR-regulated gene encoding a cell wall inhibition-responsive protein (CwrA) using electrophoretic mobility shift assays. We constructed <i>cwrA</i> deletion mutants in the genetic background of methicillin-resistant <i>S. aureus</i> (MRSA) and methicillin-sensitive <i>S. aureus</i> (MSSA) strains. Phenotypic analyses indicated that deletion of <i>cwrA</i> led to impaired biofilm formation, which was correlated with polysaccharide intercellular adhesin (PIA). Besides, the results of real-time quantitative PCR (RT-qPCR) and β-galactosidase activity assay revealed that CwrA promoted biofilm formation by influence the <i>ica</i> operon activity in <i>S. aureus</i>. Furthermore, <i>cwrA</i> deletion mutants released less extracellular DNA (eDNA) in the biofilm because of their reduced autolytic activity compared to the wild-type (WT) strains. We also found that <i>cwrA</i> deletion mutant more virulence than the parental strain because of its enhanced hemolytic activity. Mechanistically, this phenotypic alteration is related to activation of the SaeRS two-component system, which positively regulates the transcriptional levels of genes encoding membrane-damaging toxins. Overall, our results suggest that CwrA plays an important role in modulating biofilm formation and hemolytic activity in <i>S. aureus</i>.