Identification of the amino acids essential for LytSR ‐mediated signal transduction in S taphylococcus aureus and their roles in biofilm‐specific gene expression

Abstract

Summary: Recent studies have demonstrated that expression of the S taphylococcus aureus lrgAB operon is specifically localized within tower structures during biofilm development. To gain a better understanding of the mechanisms underlying this spatial control of lrgAB expression, we carried out a detailed analysis of the LytSR two‐component system. Specifically, a conserved aspartic acid ( Asp 53) of the LytR response regulator was shown to be the target of phosphorylation, which resulted in enhanced binding to the lrgAB promoter and activation of transcription. In addition, we identified His 390 of the LytS histidine kinase as the site of autophosphorylation and Asn 394 as a critical amino acid involved in phosphatase activity. Interestingly, LytS ‐independent activation of LytR was observed during planktonic growth, with acetyl phosphate acting as a phosphodonor to LytR . In contrast, mutations disrupting the function of LytS prevented tower‐specific lrgAB expression, providing insight into the physiologic environment within these structures. In addition, overactivation of LytR led to increased lrgAB promoter activity during planktonic and biofilm growth and a change in biofilm morphology. Overall, the results of this study are the first to define the LytSR signal transduction pathway, as well as determine the metabolic context within biofilm tower structures that triggers these signaling events.