FIG. 4.

Effects of nickel supplementation on the transcription of selected genes in wild-type H. pylori 26695 and the HP1512::cat mutant. The levels of transcripts of four nickel-related genes were quantified after 18 h of growth in BBF supplemented with three different concentrations of NiCl₂ (1, 5, and 10 μM). HP1010, encoding polyphosphate kinase (ppk), served as a housekeeping gene control. For each transcript measured, three comparisons were made. First, for each gene investigated, its response to nickel supplementation was determined by comparing the relative levels of transcripts in wild-type H. pylori 26695 grown in 1, 5, and 10 μM supplemental NiCl₂ to the transcript level of cells grown in unsupplemented BBF (left three bars). Second, to determine whether mutation of HP1512 affected the ability of H. pylori to respond to nickel supplementation, comparisons were made between transcript levels in the HP1512 mutant with nickel supplementation of 1, 5, and 10 μM NiCl₂ relative to that in cells grown in unsupplemented BBF (right three bars). Finally, at each supplemental nickel concentration (0, 1, 5, 10 μM), the relative transcript level in the HP1512 mutant was compared to that of wild-type (wt) H. pylori 26695 to measure the effect of HP1512 mutation on nickel responsiveness (middle four bars). The values (changes [n-fold]) are reported as the averages from three independent assays.