Hydrogen is produced in the gastrointestinal tract of both rodents and humans as a by-product of colonic fermentation, but the potential for molecular hydrogen to serve as an energy reservoir for pathogenic bacteria has been poorly investigated. In November 29 Science, Jonathan Olson and colleagues at the Department of Microbiology, University of Georgia, Athens, USA, show that Helicobacter pylori — the pathogen that causes peptic ulcers in humans — use molecular hydrogen as an energy source (Science, 298:1788-1790, November 29, 2002).

Olson et al. used a mouse H. pylori colonization assay and observed that hydrogen was available in the gastric mucosa of mice and that its use greatly increased stomach colonization by H. pylori. In addition, they showed that a hydrogenase mutant strain of H. pylori, which cannot use hydrogen as an energy source, was much less efficient in its colonization of the...