FIG 5 .

ChePep regulates H. pylori chemotaxis response in a pH gradient. (A) A microscopic pH gradient generated by a microinjection needle is visualized by Lysosensor dye fluorescence (pseudocolor image) (see Fig. S4 in the supplemental material for details). (B) A sample frame from a movie of WT bacteria and their motility tracings after 20 s in the pH gradient is shown. Rings are 10 µm apart. (C) The distance of each H. pylori cell to the acid point source is plotted before (−) or 10 s after (+) exposure to the pH gradient; ChePep* is ∆ChePep complemented in trans. NS, no statistical difference. (D) Plot of the percentage of H. pylori cells remaining within 60 µm of the micropipette tip over time. One hundred percent is defined as the number of bacteria within this radius directly before addition of acid. Error bars indicate standard deviations from the mean of five independent movies. Results for the ∆ChePep mutant and WT strains are significantly different (P < 0.0001, F test). (E) Bacterial motility paths of WT versus different mutants 2 s before (upper panels) and after 10 s in the pH gradient (bottom panels) (see Movie S5 in the supplemental material).