文摘
Staphylococcus xylosus is a saprophytic bacterium commonly found on skin of mammals but alsoused for its organoleptic properties in manufacturing of fermented meat products. This bacterium isable to form biofilms and to colonize biotic or abiotic surfaces, processes which are mediated, to acertain extent, by cell-envelope proteins. Thus, the present investigation aimed at evaluating andadapting different existing methods for cell-envelope subproteome analyses of the strain S. xylosusC2a. The protocol selected consisted initially of a lysostaphin treatment producing protoplasts andgiving a fraction I enriched in cell wall proteins. A second fraction enriched in membrane proteins wasthen efficiently recovered by a procedure involving delipidation with a mixture of tributyl phosphate,methanol, and acetone and solubilization with a buffer containing ASB14. Proteins were separatedusing two-dimensional gel electrophoresis (2-DE) and identified using matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS). A total of 168 protein spots was identifiedcorresponding to 90 distinct proteins. To categorize and analyze these proteomic data, a rationalbioinformatic approach was carried out on proteins identified within cell envelope of S. xylosus C2a.Thirty-four proteins were predicted as membrane-associated with 91% present, as expected, withinfraction II enriched in membrane proteins: 24 proteins were predicted as membranal, 3 as lipoproteins,and 7 as components of membrane protein complex. Eighteen out of 25 (72%) proteins predicted assecreted were indeed identified in fraction I enriched in cell wall proteins: 6 proteins were predictedas secreted via Sec translocon, and the remaining 19 proteins were predicted as secreted via unknownsecretion system. Eighty-one percent (25/31) of proteins predicted as cytoplasmic were found in fractionII: 8 were clearly predicted as interacting temporarily with membrane components. By couplingconventional 2-DE and bioinformatic analysis, the approach developed allows fractionating, resolving,and analyzing a significant and important set of cell envelope proteins from a coagulase-negativestaphylococcus, that is, S. xylosus C2a.