Characterization in <i>Helicobacter pylori</i> of a Nickel Transporter Essential for Colonization That Was Acquired during Evolution by Gastric <i>Helicobacter</i> Species

<div><p>Metal acquisition is crucial for all cells and for the virulence of many bacterial pathogens. In particular, nickel is a virulence determinant for the human gastric pathogen <i>Helicobacter pylori</i> as it is the cofactor of two enzymes essential for <i>in vivo</i> colonization, urease and a [NiFe] hydrogenase. To import nickel despite its scarcity in the human body, <i>H</i>. <i>pylori</i> requires efficient uptake mechanisms that are only partially defined. Indeed, alternative ways of nickel entry were predicted to exist in addition to the well-described NixA permease. Using a genetic screen, we identified an ABC transporter, that we designated NiuBDE, as a novel <i>H</i>. <i>pylori</i> nickel transport system. Unmarked mutants carrying deletions of <i>nixA</i>, <i>niuD</i> and/or <i>niuB</i>, were constructed and used to measure (i) tolerance to toxic nickel exposure, (ii) intracellular nickel content by ICP-OES, (iii) transport of radioactive nickel and (iv) expression of a reporter gene controlled by nickel concentration. We demonstrated that NiuBDE and NixA function separately and are the sole nickel transporters in <i>H</i>. <i>pylori</i>. NiuBDE, but not NixA, also transports cobalt and bismuth, a metal currently used in <i>H</i>. <i>pylori</i> eradication therapy. Both NiuBDE and NixA participate in nickel-dependent urease activation at pH 5 and survival under acidic conditions mimicking those encountered in the stomach. However, only NiuBDE is able to carry out this activity at neutral pH and is essential for colonization of the mouse stomach. Phylogenomic analyses indicated that both <i>nixA</i> and <i>niuBDE</i> genes have been acquired via horizontal gene transfer by the last common ancestor of the gastric <i>Helicobacter</i> species. Our work highlights the importance of this evolutionary event for the emergence of <i>Helicobacter</i> gastric species that are adapted to the hostile environment of the stomach where the capacity of <i>Helicobacter</i> to import nickel and thereby activate urease needs to be optimized.</p>