FIG 2 .
Measurements of the bulk cytoplasmic pH and local pH near the cytoplasmic membrane at external pH 7.0. (A) The bulk pH was measured with 280 wild-type cells transformed with pYVM001 [pHluorin(M153R)]. (B to D) The local pH was measured with more than 100 fluorescent spots observed with the YVMN001 cells [ΔfliMN pHluorin(M153R)-fliG], in which neither the complete export gate nor the MotAB proton channel complex associates with the MS ring (B), and more than 200 wild-type cells transformed with pYVM093 [pHluorin(M153R)-Flk] (C) or pYVM094 [pHluorin(M153R)-MinDMTS] (D). The pH distribution was fitted by a Gaussian function. Cells were incubated at 30°C in TB until the cells had reached an OD600 of ca. 1.6 to 1.8. Intracellular pH measurements were done at ca. 23°C. The pH values were determined by the standard curves obtained from purified pHluorin(M153R) and pHluorin(M153R)-FliG-His for bulk cytoplasmic pH and local pH, respectively.