Local pH elevation mediated by the intrabacterial urease of Helicobacter pylori cocultured with gastric cells
J. Clin. Invest. Christoph Athmann, et al. 106:339 doi:10.1172/JCI9351 [Go to this article.]

Figure 2
Localization of pH elevation with urea addition at pH_out 5.5. H. pylori cocultured with AGS cells were perfused with medium containing BCECF-free acid and then 5 mM urea added as detailed in the text. Changes of fluorescence were then observed as a function of time using confocal microscopy at ×100 optical magnification and ×3 or ×10 electronic magnification. (a) The addition of 5 mM urea initially resulted in an increase of BCECF fluorescence clearly visible at the periphery of the wild-type organisms. (b) Higher magnification of a single wild-type organism emphasizing the peripheral increase of BCECF fluorescence obtained with urea addition. This restricted region of pH elevation is the periplasm. (c) Pretreatment with 0.01% C₁₂E₈ resulted in bacterial cytoplasmic alkalinization after the addition of urea to wild-type organisms. (d) Addition of 5 mM urea resulted in little or no change of fluorescence (pH) in the periplasm of the H. pylori ureI-ve mutant with the addition of 5 mM urea. (e) Pretreatment of the ureI-ve mutants with 0.01% C₁₂E₈ followed by urea addition increased cytoplasmic pH as monitored by the rise in BCECF fluorescence within the organism. The arrow points to a region where the image is electronically magnified to show the internal, compared with surface, fluorescence. Each bar corresponds to 3 μm as defined by the confocal software.