FIG. 4.

The effects of the growth stage (A) and ppGpp (B) on the induction of mazEF-mediated cell death. (A) Logarithmic (Log) and stationary (Sta) E. coli MC4100 relA⁺ cells were either left untreated (a) or submitted for 10 min to high temperature (50°C) (b), UV irradiation (c), rifampin exposure (20 μg/ml) (d), or the overproduction of MazF (e). (B) Logarithmic E. coli MC4100relA⁺ and MC4100relA1 cells were submitted for 10 min to high temperature (50°C) (a), UV irradiation (b), nalidixic acid (Nal) exposure (2 mg/ml) (c), H₂O₂ exposure (15 mM) (d), rifampin (Rif) exposure (20 μm/ml) (e), chloramphenicol (Cam) exposure (50 μg/ml) (f), or the overproduction of MazF (g). Cell viability and survivor ratios were determined as described in the legend to Fig. 1. The results represent one experiment out of three independent similar experiments.