FIG 2 .
Induction of the SOS response in stationary-phase persisters and nonpersisters is equivalent. (A) GFP induction from SOS transcriptional reporters with ofloxacin. Unshaded curves, ΔrecA mutant controls treated for 5 h with ofloxacin; shaded curves, samples treated for 5 h with ofloxacin. Events in gates C and D were considered to have responded to ofloxacin because ≤2% of the events from ofloxacin-treated ΔrecA mutant controls fell within those gates. Controls for each reporter are provided in Fig. S1 and S4 in the supplemental material. (B) Survival fractions of ofloxacin-treated cells from gates designated in panel A. T, total-population control passed through the sorter (all gates); α and β, samples diluted to postsorting cell density before and after sorting that did not themselves travel through the sorter. Sorting did not significantly reduce sample culturability. This was determined by a lack of significant difference in survival between the total sorted population (T) and the presorting (α) or postsorting (β) controls (by Student’s t test, two tails with unequal variance) for any of the SOS reporters tested. Survival fractions were calculated relative to the cell density of sorted samples, 3 × 105 cells/ml. Differences between the survival of PsulA (fractions or controls) and the other three SOS reporters were not significant for the majority of the comparisons, as determined by Student’s t test (two tails with unequal variance). Biphasic killing was observed for all strains (see Fig. S2 in the supplemental material), and reanalysis of FACS-segregated populations is provided in Fig. S5 in the supplemental material.