PR000199 (Project)

Description:Staphylococcus aureus is a significant cause of morbidity and mortality in both hospital settings and the community at-large, and methicillin-resistant S. aureus (MRSA) has been recently categorized by the CDC as a significant antibiotic-resistant threat. As such, there exists an on-going critical need to study S. aureus genes that promote growth and resistance to host immune responses, so that their encoded products can eventually be evaluated for potential as novel antimicrobial targets. In this respect, S. aureus nitric-oxide (NO) synthase (saNOS) and NO-reductase (saNOR) have been recently shown to dramatically affect the physiology of this pathogen. Specifically, nos mutants have displayed decreased virulence in both subcutaneous abscess and sepsis models of infection, and our own research has suggested that NO produced via saNOS has a negative effect on endogenous reactive oxygen species (ROS) accumulation under growth conditions promoting aerobic respiration and may regulate metabolism in an as-yet unknown fashion. Our research has also demonstrated a role for saNOR in modulating cellular NO levels when exposed to exogenous NO donor and may contribute to cellular metabolism under conditions of nitrosative stress. Therefore, overall hypothesis of this proposal is that modulation of exogenous and endogenous NO levels (by saNOR and saNOS, respectively) represent novel metabolic adaptations that contribute to S. aureus survival during infection. To this end, a global untargeted metabolomics approach will be employed to complete two research aims: Aim 1: Compare the effect of saNOR on S. aureus metabolism when grown in the presence and absence of exogenous NO. Aim 2: Identify the effects of endogenous NO produced by saNOS on S. aureus metabolism when grown under conditions promoting aerobic respiration. These proposed studies will help catalogue the exact metabolic changes that occur as a function of saNOS and saNOR, which will help unravel the upstream regulatory circuits and downstream cellular targets of both of these enzymes.