Effects of bismuth exposure and iron limitation on H. pylori intracellular ATP levels. ATP levels per microgram of bacterial dry weight were determined for H. pylori 60190, SS1, and Tx-30a following growth in the presence of normal growth conditions (control), iron-limiting conditions (De), MICCBS (Bi), MICCBS plus protective iron (Bi + Fe), and protective iron alone (Fe). Data are the means and standard errors of two independent experiments performed in duplicate. An asterisk indicates that the result is statistically significantly different (P < 0.05) from that for control (untreated) bacteria.