Heterogeneity in ess transcriptional organization and variable contribution of the Ess/Type VII protein secretion system to virulence across closely related Staphylocccus aureus strains

Holger Kneuper, Zhen Ping Cao, Kate B. Twomey, Martin Zoltner, Franziska Jäger, James S. Cargill, James Chalmers, Magdalena M. van der Kooi-Pol, Jan Maarten van Dijl, Robert P. Ryan, William N. Hunter, Tracy Palmer (Lead / Corresponding author)

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    Abstract

    The Type VII protein secretion system, found in Gram-positive bacteria, secretes small proteins, containing a conserved W-x-G amino acid sequence motif, to the growth medium. Staphylococcus aureus has a conserved Type VII secretion system, termed Ess, which is dispensable for laboratory growth but required for virulence. In this study we show that there are unexpected differences in the organization of the ess gene cluster between closely related strains of S. aureus. We further show that in laboratory growth medium different strains of S. aureus secrete the EsxA and EsxC substrate proteins at different growth points, and that the Ess system in strain Newman is inactive under these conditions. Systematic deletion analysis in S. aureus RN6390 is consistent with the EsaA, EsaB, EssA, EssB, EssC and EsxA proteins comprising core components of the secretion machinery in this strain. Finally we demonstrate that the Ess secretion machinery of two S. aureus strains, RN6390 and COL, is important for nasal colonization and virulence in the murine lung pneumonia model. Surprisingly, however, the secretion system plays no role in the virulence of strain SA113 under the same conditions.
    Original languageEnglish
    Pages (from-to)928-943
    Number of pages15
    JournalMolecular Microbiology
    Volume93
    Issue number5
    Early online date8 Jul 2014
    DOIs
    Publication statusPublished - 30 Jul 2014

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