FIG 7.
Urea increases the intracellular pH in acidic medium. Cultures of H. pylori strains G27/PcagA-KapA-Δtat-EGFP (A) and G27/PcagA-TorA-EGFP (B) were harvested and suspended in 5 mM HP medium buffers, adjusted to pH 7.5, 6.5, and 5.0. At 60 s, 5 mM urea was added, and the fluorescence signal was converted to pH units, as described in Materials and Methods. Signals were averaged for three independent cultures under each condition. Error bars at 60, 70, and 210 s represent standard deviations of means (n = 3), and they are within the data point if not visible. pHex indicates external pH.