Figure 3
The frequency of E. coli persisters is not affected by (a) non-biological ionophores (CCCP and DNP) before ciprofloxacin treatment or (b) indole before novobiocin treatment. (a) Percentage survival of exponential-phase (OD600 = 0.15) BW25113 ∆tnaA E. coli in LB medium treated for 20 min with 100 µM CCCP or 800 µM DNP, then washed and resuspended in fresh LB and treated for five hours with 100 × MIC ciprofloxacin. Data for the percentage survival of BW25113 wild-type and ∆tnaA, with and without an indole pulse (Figs. 1 and 2), are included for comparison. All data are the mean ± SD of a minimum of three biological replicates. (b) Percentage survival of exponential-phase (OD600 = 0.15) wild-type (indole-positive) and ΔtnaA (indole-negative) strains of BW25113 E. coli in LB medium treated for five hours with 100 × MIC novobiocin. For indole supplementation, prior to antibiotic addition, ΔtnaA cultures were supplemented with 0.5 mM indole. To mimic an indole pulse prior to antibiotic addition, ΔtnaA cultures were treated for 20 min with 5 mM indole then washed and resuspended in fresh LB. All data are the mean ± SD of a minimum of three biological replicates.
