Fig. 2.
Fitness advantage of agr mutants. (A) Aerobic growth of HG001, agr, agrCR238H (constitutive agr), and agrAR165H in tryptic soy broth (TSB). Error bars represent SD (n = 3). (B) HG001 and agrCR238H evolved for 2 and 3 d with and without sub-MIC of ciprofloxacin (0.125 µg/mL). Percentage of nonhemolytic and hemolytic subpopulations was determined based on colony phenotype on blood agar. Error bars indicate SEM (n = 3). Statistical significance determined by two-way ANOVA with Tukey’s posttest. *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, and ****P ≤ 0.0001.