The antimicrobial peptide-sensing system aps of Staphylococcus aureus

Area of Science:

• Microbiology
• Infectious Diseases
• Bacterial Pathogenesis

Background:

• Staphylococcus aureus, particularly community-associated methicillin-resistant strains (CA-MRSA), causes significant human infections.
• Bacterial survival hinges on evading host innate immune defenses, including antimicrobial peptides (AMPs).

Purpose of the Study:

• To investigate the role of the aps sensor/regulator system in mediating CA-MRSA resistance to AMPs.
• To elucidate the specific resistance mechanisms induced by AMPs in S. aureus.
• To compare the aps system's function in S. aureus versus S. epidermidis and assess its in vivo relevance.

Main Methods:

• Induction of resistance mechanisms in CA-MRSA by AMPs.
• Analysis of teichoic acid d-alanylation and bacterial membrane modifications.
• Functional characterization of the vraFG transporter in AMP resistance.
• Comparative analysis of the ApsS sensor protein structure and AMP binding.
• Evaluation of the aps system's role in a murine infection model.

Main Results:

• AMPs induce d-alanylation of teichoic acids, lysyl-phosphatidylglycerol incorporation, and increased lysine biosynthesis in CA-MRSA.
• The vraFG transporter was identified as a functional component of AMP resistance.
• S. aureus's aps response is AMP-selective due to structural variations in the ApsS sensor, unlike in S. epidermidis.
• The aps regulatory system is essential for S. aureus virulence in a murine infection model.

Conclusions:

• The aps system is a key regulator of AMP resistance in S. aureus, employing multiple defense strategies.
• Interspecies differences in AMP-Sensing highlight the specificity of bacterial host defense evasion.
• Targeting the aps system could be a strategy to combat S. aureus infections.