Introduction to Type VII Secretion System (T7SS) of Staphylococcus aureus

Abstract

The aim of this chapter was to investigate the genetic diversity of the T7SS across Staphylococcus aureus strains and its role in virulence and interbacterial competition. The ess locus is responsible for encoding the type VII protein secretion system (T7SS) in Staphylococcus aureus. A crucial player within this system is EssC, a membrane-bound ATPase with multiple domains crucial for substrate identification and protein transport via the T7SS. Moreover, it plays a pivotal role in intraspecies competition by secreting toxins capable of depolarising membranes and nucleases, thereby inhibiting the growth of strains lacking neutralising immunity proteins. The findings from the genomic analysis revealed that the T7SS is situated within genomic clusters housing an array of toxin and immunity genes, indicating robust conservation of this system among staphylococci species. Notably, in species like Staphylococcus warneri, where the T7SS is absent, there are genomic islands harbouring diverse immune protein-encoding genes. This observation underscores the pivotal role of the secretion system in mediating bacterial antagonistic interactions within microbial communities. The T7SS is a crucial system for Staphylococcus aureus, contributing to its virulence and enabling it to outcompete with other strains through the secretion of toxins and nucleases.