Characterization of the sigma(B) regulon in Staphylococcus aureus

Area of Science:

• Microbiology
• Bacterial Genetics
• Stress Response Mechanisms

Background:

• Gram-positive bacteria possess a sigma(B)-dependent stress regulon with potential roles in virulence.
• The sigma(S) regulon in Gram-negative bacteria (e.g., Escherichia coli) serves as a functional analogue.
• Understanding the sigma(B) regulon in Staphylococcus aureus is key to elucidating its virulence control.

Purpose of the Study:

• To identify sigma(B)-dependent stress genes in Staphylococcus aureus.
• To investigate the function of the sigma(B) regulon, particularly in virulence control.
• To provide evidence for the physiological role of the sigma(B) regulon.

Main Methods:

• Comparative two-dimensional protein electrophoresis of wild-type S. aureus COL and an isogenic sigB mutant.
• N-terminal sequencing of identified proteins to map genes on the S. aureus genome.
• Transcriptional analysis of candidate genes to confirm sigma(B) dependency and operon structures.

Main Results:

• Approximately 27 cytoplasmic proteins were found to be under positive sigma(B) control.
• 23 sigma(B)-dependent genes and their corresponding proteins were identified.
• Identified proteins are potentially involved in NADH generation and membrane transport; one clpC-homologous gene is solely sigma(B)-transcribed.

Conclusions:

• The sigma(B) regulon plays a significant role in Staphylococcus aureus stress response and potentially virulence.
• Identification of 23 sigma(B)-dependent genes provides a foundation for further functional studies.
• Differential expression of clpC-homologous genes highlights complex regulatory networks in S. aureus.