FIG. 1.
pHin of H. pylori measured after 8 min of incubation in citrate-phoshate buffer at the appropriate pHout. (A) Apparent pHin; (B) pHin after correction for binding as described by Zaritsky et al. (38); (C) ΔpH (corrected values). Open circles, cells in the absence of urea; solid circles, cells in the presence of 20 mM urea; gray circles, cells with urea and 1 mM 2,4-DNP. The ratio of accumulation of 14C in the cells to accumulation of 14C in the medium (ATin/ATout) was 280 ± 67 for pH 1 in the presence of urea, while it was only 10 ± 1 at pH 1 in the presence of urea and 2,4-DNP. At pH 7 ATin/ATout was around 2 ± 0.5, irrespective of the presence of urea or 2,4-DNP, indicating that the pHin approximately matched the pHout.