FIG 4 .

Effect of depletion of FliH and FliI on the bulk cytoplasmic pH and local pH near the export apparatus. (A) Measurements of the bulk cytoplasmic pH of SJW1103 (wild type [WT]) and MMHI0117 (ΔfliHI flhB*) cells transformed with pYVM001 at external pH 7.0 (n = 280 cells). P values were calculated using a two-tailed t test. (B) Measurements of the local pH of the ΔfliH-fliI flhB(P28T) pH-fliG (YVM1049) (red line) and YVM1063 (flhB* pH-fliG) (blue line) cells at external pH 7.0. The local pH was measured with more than 200 fluorescent spots. The pH distribution was fitted by a Gaussian function. The local pH distribution of YVM1004 (pH-fliG) is also shown by a black dashed line as a reference. All cells were incubated at 30°C in TB until the culture medium had reached an OD₆₀₀ of ca. 1.6 to 1.8. All measurements were done at ca. 23°C. (C) Measurements of local pH of YVM1070 (ΔfliI pH-fliG) carrying pTrc99A (V, black line), pMM1702 (WT, light blue line), pKK211 (E211Q, green line), or pMM1702(E211D) (E211D, orange line) at external pH 7.0. More than 100 fluorescent spots were counted for each strain.