CidR and CcpA Synergistically Regulate Staphylococcus aureus cidABC Expression

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Genetics

Background:

• Subpopulation cell death and lysis in Staphylococcus aureus biofilms release extracellular DNA, benefiting the entire population.
• The cidABC operon is implicated in these processes, with its expression controlled by the LysR-type transcriptional regulator CidR.

Purpose of the Study:

• To characterize cis- and trans-acting elements essential for cidABC operon induction in S. aureus.
• To investigate the role of catabolite control protein A (CcpA) in regulating cidABC expression.

Main Methods:

• Sequence analysis to identify potential regulatory elements (CidR-binding site, cre box).
• Electrophoretic mobility shift assays (EMSA) and real-time reverse transcriptase PCR (RT-PCR) to confirm CcpA interaction.
• Analysis of P-reporter fusions in mutant strains to assess the role of CcpA and the cre site in cidABC induction.

Main Results:

• A CidR-binding site and a catabolite responsive element (cre box) were identified in the cidABC promoter region.
• CcpA directly and positively controls cidABC transcription, demonstrating its role as a master regulator of carbon metabolism.
• Both CidR and CcpA are necessary for full cidABC operon induction, highlighting synergistic control.

Conclusions:

• The study demonstrates the synergistic control of cidABC operon expression by CidR and CcpA in S. aureus.
• Full induction of cidABC expression is dependent on the bacterial metabolic state and requires both transcriptional regulators.
• These findings provide new insights into the regulation of cell death during S. aureus biofilm development.