CidR and CcpA Synergistically Regulate Staphylococcus Aureus Expression

The death and lysis of a subpopulation of cells during biofilm development benefit the whole bacterial population through the release of an important component of the biofilm matrix, extracellular DNA. Previously, we have demonstrated that these processes are affected by the gene products of the operon, the expression of which is controlled by the LysR-type transcriptional regulator, CidR. In this study, we characterized - and -acting elements essential for the induction of the operon. In addition to a CidR-binding site located within the promoter region, sequence analysis revealed the presence of a putative catabolite responsive element ( box), suggestive of the involvement of the catabolite control protein A (CcpA) in the regulation of expression. This was confirmed using electrophoretic mobility shift assays and real-time reverse transcriptase PCR analysis demonstrating the direct positive control of transcription by the master regulator of carbon metabolism. Furthermore, the importance of CcpA and the identified site for the induction of the operon was demonstrated by examining the expression of P reporter fusions in various mutant strains in which the genes involved in carbon metabolism and carbon catabolite repression were disrupted. Together the results of this study demonstrate the necessity of both transcriptional regulators, CidR and CcpA, for the induction of the operon and reveal the complexity of molecular interactions controlling its expression. This work focuses on the characterization of - and -acting elements essential for the induction of the operon in The results of this study are the first to demonstrate the synergistic control of expression by transcriptional regulators CidR and CcpA during carbohydrate metabolism. We established that the full induction of expression depends on the metabolic state of bacteria and requires both CidR and CcpA. Together, these findings delineate regulatory control of expression under different metabolic conditions and provide important new insights into our understanding of cell death mechanisms during biofilm development in .