Figure 4.

Superoxide dismutases affect TisB-dependent persister formation and recovery. Mid-exponential cultures were treated with ciprofloxacin (1,000x MIC, 10 µg mL⁻¹) and plated on LB agar with 10 mM thiourea but without antibiotics to monitor CFU counts and colony growth. (a) CFU counts were determined at 0 hours and 4 hours to calculate persister levels in wild type (wt), strain Δ1-41 ΔistR (ΔΔ), and respective sodA and sodB deletions (SodAB⁻). Data represents the mean and error bars depict the standard deviation (n ≥ 7). For statistical analysis robust ANOVA⁵⁸ was performed. Significance levels are indicated (ns: not significant, **P < 0.01). (b) ScanLag analysis of colony growth on LB agar after 4 hours of ciprofloxacin treatment. Appearance time indicates the first detection events of individual colonies (see Methods). Corresponding colony growth time can be found in Supplementary Figure S8. Pairwise Wilcoxon rank sum test was applied (**P < 0.01). Wild type (wt, n = 339), wt SodAB⁻ (n = 314), Δ1-41 ΔistR (ΔΔ, n = 1076), and ΔΔ SodAB⁻ (n = 561). (c) Killing kinetics of persister subpopulation. CFU counts were determined at 4, 8, 12, and 24 hours. Persister levels were calculated relative to 4-hours samples for strain Δ1-41 ΔistR (ΔΔ) and ΔΔ SodAB⁻. Student’s t-test compares ΔΔ versus ΔΔ SodAB⁻ for each time point (ns: not significant, *P < 0.05, **P < 0.01).