CcpA mediates proline auxotrophy and is required for Staphylococcus aureus pathogenesis

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Pathogenesis

Background:

• Clinical isolates of Staphylococcus aureus, including strains Newman and N315, exhibit proline auxotrophy despite possessing genes for proline synthesis.
• This auxotrophy suggests a regulatory mechanism controlling proline biosynthesis in S. aureus.

Purpose of the Study:

• To investigate the genetic basis of proline auxotrophy in Staphylococcus aureus.
• To elucidate the role of carbon catabolite repression (CCR) in regulating proline biosynthesis and its impact on S. aureus pathogenesis.

Main Methods:

• Generation and analysis of S. aureus Newman variants with mutations in regulatory genes (ccpA, ptsH) and proline synthesis pathway genes (rocF, rocD, proC, ocd).
• Assessment of proline prototrophy in generated variants.
• Analysis of CcpA binding to gene promoter regions and its interaction with phosphorylated HPr.
• Evaluation of S. aureus load and replication in a murine model of abscess formation using a ccpA mutant.

Main Results:

• Proline-prototrophic S. aureus Newman variants arose via mutations in ccpA or ptsH, genes involved in CCR.
• Mutations in rocF, rocD, but not proC or ocd, abolished the generation of proline-prototrophic variants.
• CcpA represses transcription of rocF and rocD, with binding enhanced by phosphorylated HPr.
• The ccpA mutant showed reduced bacterial load and replication in a murine abscess model.

Conclusions:

• Carbon catabolite repression (CCR), mediated by CcpA, is a key factor in Staphylococcus aureus proline auxotrophy.
• CCR plays a significant role in S. aureus infection pathogenesis.
• Targeting CCR pathways could be a potential strategy to combat S. aureus infections.