Figure 5: Nature Communications

Fig. 5

From: Non-canonical activation of OmpR drives acid and osmotic stress responses in single bacterial cells

Fig. 5

OmpR regulation of intracellular pH is non-canonical. a Phosphorylation of EnvZc is acid sensitive. Phosphorylation of E. coli EnvZc compared with S. Typhimurium EnvZc at pH 7.5 and 5.5. The indicated reaction times are above the panel and the percent phosphorylation (determined by densitometry) is listed below. b Representative epifluorescence ratio images (R488/440) were obtained for wild type, an ompR null, an envZ null strain, and the envZ null complemented with envZc (encoding the cytoplasmic domain of EnvZ), and an envZ null complemented with envZcC277Y in S. Typhimurium. Cells were incubated at either acidic pHe 5.6 or pHe 7.2 in the presence of 15% (w/v) sucrose. Scale bar, 3 µm. c A plot of the intracellular pH of 50 cells of wild-type and S. Typhimurium mutants at each indicated time point. Error bars represent the mean ± s.e.m. (n = 3). d, e OmpR binding to DNA is pH sensitive. AFM images of the 700 bp ompC promoter (ompC 700 ) from d S. Typhimurium and e E. coli with 30 nM OmpR at acid pH and at neutral pH (the pH used was from the measured values in Fig. 1), 30 nM OmpR~P (phosphorylated by acetyl phosphate), and 30 nM (EnvZc + OmpR) at different pHe values. The lengths of the ompC promoter in S. Typhimurium and E. coli were similar (Supplementary Fig. 9h, i)