For their discovery of ulcer-causing bacteria, Australian doctors J. Robin Warren and Barry Marshall have received the 2005 Nobel Prize in Physiology or Medicine.

Until Warren and Marshall's finding in 1979, physicians thought that excess stomach acid caused by stress ate away at the stomach lining and lead to ulcers. The treatments prescribed ranged from a bland diet to drugs that blocked stomach acid production to, finally, surgery. Then, while examining tissue samples from the stomachs of ulcer patients, Warren noticed the presence of spiral-shaped bacteria. No one expected that such organisms could withstand the harsh acidic conditions in the stomach. But these crafty microbes appeared to live under the thick mucus layer of the stomachs lining and, in Warren's observations, suspiciously close to areas of inflammation. It took Warren, with the help of young trainee, Barry Marshall, until 1982 to finally cultivate the bacterium in the laboratory. Eventually, with the involvement of other researchers, the microbe was named Helicobacter pylori.

Researchers now know that about 50 percent of humans host the bacteria in their stomachs. Fortunately, not every person who has the microbe in residence will experience ulcers, but symptoms do occur in some 10 to 15 percent of those who do. H. pylori creates problems, because it naturally releases chemicals that attract cells that induce stomach irritation. The organism is also a good swimmer and easily evades the stomach's muscle contractions, which work to flush out other contents. Without treatment, the bacteria can cause large ulcers and also predispose a person to stomach cancer.

Today, the most effective remedy for ulcers is a regimen of antibiotics. There is some debate that eradicating the bacteria could lead to other diseases, including those of the esophagus. But the finding that a common disease of the stomach is linked to a microbe holds the promise of pinpointing the source of other chronic inflammatory conditions such as Crohn's disease, ulcerative colitis, rheumatoid arthritis and atherosclerosis.