Fig 3. Optimization of an assay to select for mutant fitness during NO· stress.

Known NO· sensitive mutants in S. aureus LAC were mixed with WT at a ratio of 1:100. Mixed cultures were serially passaged either A. aerobically or B. with 5mM DETA/NO. Every 12-hrs (for NO· exposed) or 5-hrs (for aerobic), cultures were diluted 1:100 into fresh media (with or without DETA/NO) and were plated on selective media for cfu enumeration. Asterisks indicate the generation at which the mutant becomes significantly underrepresented from the initial 1:100 ratio (n = 3 for each mutant, Student’s t-test).