RNA expression levels of JMUB217-derived mutants. qRT-PCR results for (A) mecA, (C) purF, and (D) guaA in six JMUB217-derived mutants with reduced oxacillin susceptibility: rpiA (JMUB217-7 RpiAA64E), fruB (JMUB217-13 FruBA211E), rpoB1 (JMUB217-23 RpoBH929P), rpoB2 (JMUB217-22 RpoBQ645H), rpoC1 (JMUB217-19 RpoCG950R), and rpoC2 (JMUB217-24 RpoCG498D); three mutation-repaired strains (rpiA, rpoB2, and rpoC2); and two reference MRSA strains COL and USA300_C02 with or without exposure to 100 ng/mL oxacillin. The data are shown as means ± SD of three biological replicates. *, **, ***, and ns indicate P < 0.05, 0.01, 0.001, and not significant, respectively, given by the Student’s t-test. (B) Purine biosynthesis pathway of S. aureus JMUB217.