Figure 5
Kinetics of nucleotide upon mupirocin-induced stringent response. Intracellular nucleotides of E. coli cultures growing in defined minimal medium (MOPS 0.4% glc at 37 C with vigorous aeration) were measured both prior to and after the addition of mupirocin (3-times the MIC, 150 µg/ml, added when cells reached OD600 0.5) at time point zero. The nucleotide concentrations are expressed as ratios of the guanosine, adenosine, and NTP pools as indicated in the insert; AEC stands for adenylate energy charge. Cells were harvested by filtration and the nucleotides were extracted with acetic acid. ppGpp and pppGpp were measured using isocratic SAX and the remaining nucleotides were measured using gradient IPRP. pppGpp was below the limit of detection in unstressed cells (zero time point). Error bars indicate the standard error of the mean of biological replicates (n = 8 at timepoint zero, otherwise n = 3–4). For numeric representation of the data see Table 2.
