FIG 4.

Medium composition modulates the effects of mupirocin and ampicillin treatment on wild-type, relaxed, and ppGpp⁰ BW25113 E. coli. Experiments were performed using either filtered LB (A and C; beige shading) or MOPS medium supplemented with 0.4% glucose and a full set amino acids at 400 μg/ml (for serine) or 25 μg/ml (for the remaining 19 amino acids) (B and D; blue shading). The colony count (i.e., the CFU) was determined either as a function of a 30-min treatment with either 70 μM mupirocin compared to mock treatment (A and B) or as a function of time after the addition of ampicillin to a final concentration of 200 μg/ml (C and D). Error bars indicate the standard errors of the mean (three to five biological replicates). Where indicated by brackets, the P values were calculated using a two-tailed Welch's t test either between wild-type and mutant strains (A and B) or relative to the killing time course of an untreated culture (C and D).