title: Heterogeneity in ess transcriptional organization and variable contribution of the Ess/Type VII protein secretion system to virulence across closely related Staphylocccus aureus strains.
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.
authors.affiliation: Division of Molecular Microbiology, College of Life Sciences, University of Dundee, Dundee, UK.
authors.forename: Holger
authors.initials: H
authors.lastname: Kneuper
authors.forename: Zhen Ping
authors.initials: ZP
authors.lastname: Cao
authors.forename: Kate B
authors.initials: KB
authors.lastname: Twomey
authors.forename: Martin
authors.initials: M
authors.lastname: Zoltner
authors.forename: Franziska
authors.initials: F
authors.lastname: Jäger
authors.forename: James S
authors.initials: JS
authors.lastname: Cargill
authors.forename: James
authors.initials: J
authors.lastname: Chalmers
authors.forename: Magdalena M
authors.initials: MM
authors.lastname: van der Kooi-Pol
authors.forename: Jan Maarten
authors.initials: JM
authors.lastname: van Dijl
authors.forename: Robert P
authors.initials: RP
authors.lastname: Ryan
authors.forename: William N
authors.initials: WN
authors.lastname: Hunter
authors.forename: Tracy
authors.initials: T
authors.lastname: Palmer
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D058947:Bacterial Secretion Systems; D005260:Female; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity*; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems