The Type VII Secretion System of Staphylococcus

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Molecular Biology

Background:

• The type VII protein secretion system (T7SS) in *Staphylococcus aureus* is encoded by the *ess* locus.
• EssC, a membrane-bound ATPase, mediates T7SS substrate recognition and protein transport.
• Four distinct EssC sequence variants exist in *S. aureus* strains, each associated with specific substrate proteins.

Purpose of the Study:

• To investigate the role of *Staphylococcus aureus* T7SS in virulence and inter-bacterial competition.
• To characterize the diversity of T7SS variants and their associated substrates.
• To explore the conservation and function of T7SS across staphylococci.

Main Methods:

• Genomic survey of staphylococci to identify T7SS and associated toxin/immunity genes.
• Analysis of *ess* gene regulation during persistent infection.
• Examination of T7SS contribution to virulence in disease models and intraspecies competition.

Main Results:

• The *ess* genes are upregulated during persistent *S. aureus* infections.
• T7SS contributes to virulence and mediates intraspecies competition through toxin secretion.
• Genomic analysis reveals widespread conservation of T7SS across staphylococci, often with diverse toxin and immunity gene arrays.

Conclusions:

• The *S. aureus* T7SS, particularly EssC variants, plays a significant role in pathogenesis and bacterial antagonism.
• T7SS-mediated secretion of toxins and immunity proteins is crucial for inter-strain competition.
• The conservation of T7SS across staphylococci suggests a fundamental role in their ecological interactions and virulence.