Helicobacter pylori stores nickel to aid its host colonization.

The transition metal nickel (Ni) is critical for the pathogenicity of Helicobacter pylori. Indeed the element is a required component of two enzymes, hydrogenase and urease, that have been shown to be important for in vivo colonization of the host gastric mucosa. Urease accounts for up to 10% of the total cellular H. pylori protein content, and therefore the bacterial Ni demand is very high. H. pylori possess two small and abundant histidine-rich, Ni-binding proteins, Hpn and Hpn-like, whose physiological role in the host have not been investigated. In this study, special husbandry conditions were used to control Ni levels in the host (mouse), including the use of Ni-free versus Ni-supplemented food. The efficacy of each diet was confirmed by measuring the Ni concentrations in sera of mice fed with either diet. Colonization levels (based on rank tests) of the Δhpn Δhpn-like double mutants isolated from the mice provided Ni-deficient chow were statistically lower than those for mice given Ni in their diet. In contrast, H. pylori wild-type colonization levels were similar in both host groups (e.g., regardless of Ni levels). Our results indicate that the gastric pathogen H. pylori can utilize stored Ni via defined histidine-rich proteins to aid colonization of the host.