Fig. 5.

The SR and SOD activity confers membrane impermeability, a key determinant of stationary-phase tolerance. EtBr internalization in the presence of CCCP in A of exponential (EXP) or stationary-phase (STAT) cells, (B) stationary-phase WT and ΔSR cells carrying the pBAD-sodB (+sodB) or control (+vc) vector, or in stationary-phase WT cells ±50 µg/mL PMBN. (C) Killing of stationary-phase WT with 5 µg/mL ofloxacin ± PMBN pretreatment. All results are shown as mean ± SEM (n ≥ 6). **P < 0.01 vs. “WT+vc” or vs. “+PMBN”. (D) Correlation between bacterial viability of stationary-phase cells after ofloxacin challenge and membrane permeability, as measured by the EtBr internalization assay of the same culture before ofloxacin challenge (5 µg/mL for 10 h). Data from different strains (WT, ΔSR, ΔSR +sodB, ΔSR +sodA, +SR) noted as ● or WT +50 µg/mL PMBN noted as □, were combined and each data point (n ≥ 40) represents an independent replicate. The correlation coefficient R² was calculated using linear regression.