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Leftovers lover. Helicobacter pylori sups on hydrogen gas.

Ulcer Bacteria Gas It Up

Like people chowing on sandwiches made from Thanksgiving turkeys, stomach-based microbes slurp leftover nutrients. New research in mice shows that the bacteria that cause ulcers establish colonies in stomachs using hydrogen gas produced farther along in the gut. The work, reported in the 29 November issue of Science, shows for the first time that the bugs have a taste for hydrogen, and it suggests new ways to control the misery-inducing critters.

Helicobacter pylori causes 90% of stomach ulcers. The bacterium lives quietly in many stomachs until it for some unknown reason causes painful ulcers. Another mystery is how H. pylori can subsist in the gut. Microbiologist Robert Maier of the University of Georgia in Athens and colleagues had previously discovered an enzyme in the microbe that allows it to feed on hydrogen gas, and small amounts of the combustible have been shown to leak from the colon of rodents and humans. Intrigued, they tested whether gas that floated back to the stomach could activate the enzyme.

To determine the importance of the enzyme to the bacteria's ability to set up shop in the stomach, the team disabled the enzyme in one strain of microbe. They injected this strain and a normal strain into mouse stomachs and counted how many colonies the bacteria formed after 4 weeks. Without the ability to sip hydrogen, the bacteria established 75% fewer colonies, indicating a key role for the enzyme. Maier says other infectious bacteria such as salmonella have the enzyme. "Hydrogen might play a role in setting up bad [infections]," he says.

The insight will help in the search for ways to combat infectious bacteria, says microbiologist Frank Gherardini of the Rocky Mountain Laboratory in Hamilton, Montana. "Now we can target the particular enzyme." Microbial ecologist John Breznak of Michigan State University, East Lansing, calls the work a "nice discovery" and suggests a dietary change "that minimizes how much hydrogen gas gets to the stomach" might control the ulcer-causing bug.

Related sites
Robert Maier's lab
Information about Helicobacter from the Centers for Disease Control and Prevention