Biochemistry Graduate Program

Hydrogen sulfide (H2S) is thought to protect bacteria from oxidative stress, but a comprehensive understanding of its function in bacteria is largely unexplored. In this study, we show that the human pathogen Staphylococcus aureus (S. aureus) harbors significant effector molecules of H2S signaling, reactive sulfur species (RSS), as low molecular weight persulfides of bacillithiol, coenzyme A, and cysteine, and significant inorganic polysulfide species. We find that proteome S-sulfhydration, a post-translational modification (PTM) in H2S signaling, is widespread in S. aureus. RSS levels modulate the expression of secreted virulence factors and the cytotoxicity of the secretome, consistent with an S-sulfhydration-dependent inhibition of DNA binding by MgrA, a global virulence regulator. Two previously uncharacterized thioredoxin-like proteins, denoted TrxP and TrxQ, are S-sulfhydrated in sulfide-stressed cells and are capable of reducing protein hydrodisulfides, suggesting that this PTM is potentially regulatory in S. aureus. In conclusion, our results reveal that S. aureus harbors a pool of proteome- and metabolite-derived RSS capable of impacting protein activities and gene regulation and that H2S signaling can be sensed by global regulators to affect the expression of virulence factors.