We report on a new tool to study proteins synthesized by Staphylococcus aureus during infection of a live mouse. Traditional proteomics approaches are often unsuitable to study pathogens in vivo because highly abundant host proteins predominate. To circumvent this issue, we engineered several strains of S. aureus to have the ability to incorporate a non-canonical amino acid with a bio-orthogonal handle. Only these engineered strains of S. aureus can incorporate this amino acid into newly synthesized proteins, thus rendering these proteins chemically distinct from the host proteome, and allowing us to selectively tag and enrich for pathogenic proteins. Before enrichment of proteins tagged in vivo, we found relatively few S. aureus proteins in samples isolated from a skin infection model. After enrichment, we were able to identify 4x more proteins in total, with far greater spectra and sequence coverage per protein. We compared enriched samples from S. aureus labeled in vivo to the proteome synthesized prior to infection (in vitro). Over 1000 proteins were found in the in vitro lysates, while 484 were identified in the in vivo samples. These results represent the highest number of S. aureus proteins identified in vivo to date and, in addition to confirming many previously identified virulence factors, generate new candidates to examine for contributions to virulence.

Bio-orthogonal chemistry enables proteomic analysis of Staphylococcus aureus during mammalian infection

251st National Meeting (2016)

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