Decreased survival of mutants upon treatment with a bacteriostatic antibiotic chloramphenicol. Shown is the number of viable cells (colony forming units [CFU]) in 1 ml cell culture before addition of antibiotic (black bars) or after 18 hours of incubation in the presence of 80 μg/ml chloramphenicol (gray bars). Values shown are the average of two independent experiments. Error bars correspond to the standard deviation and are shown only if they are larger than the resolution of the figure. wt: wild-type E. coli.