Fig 4. Protection from antibiotics in growth-arrest-prone media.

(A) Survival curves of bacteria grown at indicated lactose concentrations in ampicillin-treated cultures (100 μg/ml). (B) Culture conditions favoring growth arrest enhance the presence of antibiotic tolerant cells after 20 h treatment of 32 μg/ml doxycycline (blue bars; ANOVA p = 0.003) or 100 μg/ml ampicillin (yellow bars; ANOVA p = 0.004). Survival ratios are normalized by cell densities of untreated cultures in corresponding conditions. N = 3 for each condition and the survival curve points, reporting mean ± SEM. In the final timepoint of the survival curve for 0.1 mg/ml lactose, two of the replicates were below the level of detection; the remaining replicate value is plotted.