SUMMARY
The gram-positive bacterium Staphylococcus aureus is a
frequent component of the human microbial flora that can turn into a
dangerous pathogen. As such, this organism is capable of infecting
almost every tissue and organ system in the human body. It does so by
actively exporting a variety of virulence factors to the cell surface
and extracellular milieu. Upon reaching their respective destinations,
these virulence factors have pivotal roles in the colonization and
subversion of the human host. It is therefore of major importance to
obtain a clear understanding of the protein transport pathways that are
active in S. aureus. The present review aims to provide a
state-of-the-art roadmap of staphylococcal secretomes, which include
both protein transport pathways and the extracytoplasmic proteins of
these organisms. Specifically, an overview is presented of the exported
virulence factors, pathways for protein transport, signals for cellular
protein retention or secretion, and the exoproteomes of different
S. aureus isolates. The focus is on S. aureus, but
comparisons with Staphylococcus epidermidis and other
gram-positive bacteria, such as Bacillus subtilis, are
included where appropriate. Importantly, the results of genomic and
proteomic studies on S. aureus secretomes are integrated
through a comparative “secretomics” approach, resulting
in the first definition of the core and variant secretomes of this
bacterium. While the core secretome seems to be largely employed for
general housekeeping functions which are necessary to thrive in
particular niches provided by the human host, the variant secretome
seems to contain the “gadgets” that S. aureus
needs to conquer these well-protected
niches.
Virulence factors on the surface of Gram-positive pathogens and mechanisms of host-pathogen recognition
