Proteomic exploration of SSR42 and its impact on Staphylococcus aureus virulence

Perhaps the most pivotal feature contributing to Staphylococcus aureus pathogenicity is the production of a wealth of virulence factors such as secreted toxins, adhesive proteins, and factors that aid in host immune evasion. The abundance and activity of these factors is tightly regulated by a multitude of effectors, including two-component systems, alternative sigma factors, DNA binding transcription factors, and regulatory RNAs. SSR42 is a ~1,200-nt long regulatory RNA that has been previously shown to be highly stable and abundant in stationary phase growth. To explore the role of SSR42 within the S. aureus cell, we created a full deletion mutant for this gene and performed mass spectrometry analysis on all protein fractions after 15h of growth. Following standardized bacterial growth and sample processing, peptides were analyzed using a hybrid Quadrupole-Orbitrap instrument and spectra were assigned with MaxQuant to the USA300 pan-proteome (UP000001939). When compared to wild-type, the SSR42 mutant exhibited profound changes in its proteomic landscape, suggesting that SSR42 has myriad regulatory targets across niches of function.