Figure 2.

Model of the T7SS machinery in S. aureus, spanning the inner membrane. EssA, EssB, and EssC form the core membrane complex. These integral membrane proteins create the secretion channel. EssC, an ATPase, drives the export of effector proteins, including EsxB, EsxC, and EsxD, which are secreted into the extracellular space. The EsaE chaperone facilitates the secretion of EsaD, a nuclease toxin, which is neutralized within the bacterial cell by EsaG to prevent self-damage. EsaB acts as a negative regulator, preventing secretion when not required. The extracellular secretion of effectors enables S. aureus to engage in bacterial competition and evade host immune responses.