Iron acquisition and virulence in <i>Helicobacter pylori</i>: a major role for FeoB, a high‐affinity ferrous iron transporter

<jats:p>The genome sequence of <jats:italic>Helicobacter pylori</jats:italic> suggests that this bacterium possesses several Fe acquisition systems, including both Fe<jats:sup>2+</jats:sup>‐ and Fe<jats:sup>3+</jats:sup>‐citrate transporters. The role of these transporters was investigated by generating insertion mutants in <jats:italic>feoB</jats:italic>, <jats:italic>tonB</jats:italic>, <jats:italic>fecA1</jats:italic> and <jats:italic>fecDE</jats:italic>. Fe transport in the <jats:italic>feoB</jats:italic> mutant was ≈ 10‐fold lower than in the wild type (with 0.5 μM Fe), irrespective of whether Fe was supplied in the Fe<jats:sup>2+</jats:sup> or Fe<jats:sup>3+</jats:sup> form. In contrast, transport rates were unaffected by the other mutations. Complementation of the <jats:italic>feoB</jats:italic> mutation fully restored both Fe<jats:sup>2+</jats:sup> and Fe<jats:sup>3+</jats:sup> transport. The growth inhibition exhibited by the <jats:italic>feoB</jats:italic> mutant in Fe‐deficient media was relieved by human holo‐transferrin, holo‐lactoferrin and Fe<jats:sup>3+</jats:sup>‐dicitrate, but not by FeSO<jats:sub>4</jats:sub>. The <jats:italic>feoB</jats:italic> mutant had less cellular Fe and was more sensitive to growth inhibition by transition metals in comparison with the wild type. Biphasic kinetics of Fe<jats:sup>2+</jats:sup> transport in the wild type suggested the presence of high‐ and low‐affinity uptake systems. The high‐affinity system (apparent <jats:bold>K</jats:bold><jats:sub>s</jats:sub> = 0.54 μM) is absent in the <jats:italic>feoB</jats:italic> mutant. Transport via FeoB is highly specific for Fe<jats:sup>2+</jats:sup> and was inhibited by FCCP, DCCD and vanadate, indicating an active process energized by ATP. Ferrozine inhibition of Fe<jats:sup>2+</jats:sup> and Fe<jats:sup>3+</jats:sup> uptake implied the concerted involvement of both an Fe<jats:sup>3+</jats:sup> reductase and FeoB in the uptake of Fe supplied as Fe<jats:sup>3+</jats:sup>. Taken together, the results are consistent with FeoB‐mediated Fe<jats:sup>2+</jats:sup> uptake being a major pathway for <jats:bold><jats:italic>H. pylori</jats:italic></jats:bold> Fe acquisition. <jats:bold><jats:italic>feoB</jats:italic></jats:bold> mutants were unable to colonize the gastric mucosa of mice, indicating that FeoB makes an important contribution to Fe acquisition by <jats:bold><jats:italic>H. pylori</jats:italic></jats:bold> in the low‐pH, low‐O<jats:sub>2</jats:sub> environment of the stomach.</jats:p>