Regulatory Requirements for Staphylococcus aureus Nitric Oxide Resistance

The ability ofStaphylococcus aureus to resist host innate immunity augments the severity and pervasiveness of its pathogenesis. Nitric oxide (NO˙) is an innate immune radical that is critical for the efficient clearance of a wide range of microbial pathogens. Exposure of microbes to NO˙ typically results in growth inhibition and induction of stress regulons.S. aureus , however, induces a metabolic state in response to NO˙ that allows for continued replication and precludes stress regulon induction. The regulatory factors mediating this distinctive response remain largely undefined. Here, we employ a targeted transposon screen and transcriptomics to identify and characterize five regulons essential for NO˙ resistance inS. aureus : three virulence regulons not formerly associated with NO˙ resistance, SarA, CodY, and Rot, as well as two regulons with established roles, Fur and SrrAB. We provide new insights into the contributions of Fur and SrrAB during NO˙ stress and show that theS. aureus ΔsarA mutant, the most sensitive of the newly identified mutants, exhibits metabolic dysfunction and widespread transcriptional dysregulation following NO˙ exposure. Altogether, our results broadly characterize the regulatory requirements for NO˙ resistance inS. aureus and suggest an intriguing overlap between the regulation of NO˙ resistance and virulence in this well-adapted human pathogen.IMPORTANCE The prolific human pathogenStaphylococcus aureus is uniquely capable of resisting the antimicrobial radical nitric oxide (NO˙), a crucial component of the innate immune response. However, a complete understanding of howS. aureus regulates an effective response to NO˙ is lacking. Here, we implicate three central virulence regulators, SarA, CodY, and Rot, as major players in theS. aureus NO˙ response. Additionally, we elaborate on the contribution of two regulators, SrrAB and Fur, already known to play a crucial role inS. aureus NO˙ resistance. Our study sheds light on a unique facet ofS. aureus pathogenicity and demonstrates that the transcriptional response ofS. aureus to NO˙ is highly pleiotropic and intrinsically tied to metabolism and virulence regulation.