FIG 1.

Antibiotic persistence increases when quality control is present, and the stringent response is disrupted. Persistence assays were done with wild-type pheS/pheT, pheT G318W, pheS A294G, and pheS A294S in both E. coli MG1655 relA⁺ (solid bars) and a XΔrelA -36292-8262-3643 strain (striped bars). Persistence was measured and quantified after 3 h of exposure to 100 μg/ml ampicillin and is shown on a log scale set relative to wild-type pheS/pheT in the relA⁺ background grown in medium A. Medium A (blue) is a supplemented M9 minimal medium that contains 40 μg/ml of all 20 proteogenic amino acids, and medium B (green) is a supplemented M9 minimal medium with 40 μg/ml of 18 proteogenic amino acids, 10 μg/ml Tyr, 40 μg/ml m-Tyr, and no Phe. Error bars represent standard deviations from 3 biological replicates. WT pheS/pheT relA⁺ in medium A and medium B is significant to pheS A294G ΔrelA in medium B with a P value of <0.03. All data sets are significant to pheS A294S ΔrelA in medium B with a P value of <0.0001, except for pheS A294G ΔrelA in medium B with a P value of 0.0008. Statistical analysis was performed using two-way analysis of variance (ANOVA).