Figure 7.

Expression of rib genes in ampicillin-treated E. coli cells. (a) The promoters of lacZ (dark blue), ribA (green), ribB (violet), ribC (light blue) and ribE (orange) genes were fused to the gene coding for the fast-folding green fluorescent protein (GFP). The promoter of the lacZ gene was induced with IPTG (red). E. coli MG1655 strains (MIC ampicillin = 2 mg/L) carrying plasmids with these transcription reporter fusions were grown with a range of ampicillin concentrations. After 3 hours of incubation, GFP fluorescence (λ_ex 488/9/λ_em 525/20 nm) and OD_600 nm of treated cells and non-treated control were measured using a fluorimeter. The fluorescence increase was calculated using the non-treated control of each strain as reference. (b) Wild type BW25113 strain and its ∆yeeO derivative were treated with a range of ampicillin concentrations during exponential growth. Autofluorescence (λ_ex 440/9/λ_em 525/20 nm) and OD_600nm of treated cells and non-treated controls were measured using a fluorimeter. To calculate the increase in the autofluorescence due to ampicillin treatment, autofluorescence of treated cells was first normalized by OD_600nm and then by the normalized autofluorescence of the non-treated controls of each strain. Each value represents the mean (+/−standard error) of the fluorescence increase from six independent experiments. The asterisk represents significant differences with the lacZ control according to unpaired t-test p value: < 0.05.