Metabolic sensor governing bacterial virulence in Staphylococcus aureus

Area of Science:

• Microbiology
• Molecular Biology
• Pathogenesis

Background:

• Effective metabolism is crucial for bacterial survival and virulence.
• Staphylococcus aureus requires metabolic coordination for proliferation and virulence factor production during infection.
• The link between S. aureus's metabolic state and virulence regulation is not well understood.

Purpose of the Study:

• To investigate the role of citrate in regulating Staphylococcus aureus metabolism and virulence.
• To identify the molecular mechanism by which citrate influences virulence gene expression.
• To elucidate the function of catabolite control protein E (CcpE) in linking metabolism to pathogenesis.

Main Methods:

• Biochemical assays to study citrate binding and activation of CcpE.
• Structural and site-directed mutagenesis studies to identify key residues in CcpE.
• Microarray analysis to determine the CcpE regulon.
• Phenotypic analysis of CcpE inactivation mutants in vitro and in vivo.

Main Results:

• Citrate directly binds to and activates the catabolite control protein E (CcpE) in S. aureus.
• Specific arginine residues (Arg145 and Arg256) in CcpE are critical for citrate-mediated activation.
• CcpE regulates 126 genes, predominantly involved in S. aureus pathogenesis, not TCA cycle activity.
• Loss of CcpE function enhances staphyloxanthin production, iron acquisition, resistance to host killing, and overall virulence in a mouse model.

Conclusions:

• CcpE acts as a metabolic sensor, linking citrate levels to the regulation of virulence factors in S. aureus.
• This metabolic control allows S. aureus to coordinate its virulence gene expression with its metabolic state for effective infection.
• CcpE is a key regulator of S. aureus pathogenesis, highlighting a critical metabolic checkpoint for virulence.