FIGURE 6.
GltA is not involved in intracellular acidification. S. Typhimurium and E. coli cultures were incubated with 20 μM BCECF for 60 min before imaging. Representative epifluorescence ratio images (R488/440) of emission channel 525 nm upon 488 and 440 nm excitation were obtained for wild type, an ompR null mutant, a gltA null mutant, an ompR/gltA null strain and a gltA over-expressed strain of (A) S. Typhimurium and (C) E. coli incubated at either acid pHe (5.6), pHe (7.2), or pHe (7.2) plus 15% (w/v) sucrose. Using ImageJ software, ratio images were color coded blue (ratio = 0.1) to white (ratio = 1). Scale bar, 3 μm. A plot of the intracellular pH of 50 cells of wild-type and mutants of (B) S. Typhimurium and (D) E. coli at each indicated time point. Error bars represent the mean ± s.e.m. (n = 3).