'The standard teaching in medicine was that ... the stomach was sterile and nothing grew there because of corrosive gastric juices. So everybody believed there were no bacteria in the stomach. When I said they were there, no one believed it.'

The 1982 discovery transformed peptic ulcer disease from a chronic, frequently disabling condition to one that can be cured by a short course of antibiotics instead of surgery, the Swedish Nobel Prize committee said in announcing the prize.

Warren was the first to observe small curved bacterium in the lower part of the stomach in many patients with ulcers. Marshall later deliberately infected himself with the microbe to show that it caused ulcers in humans.

The Prepared Mind

The breakthrough was in part accidental.

Marshall at first failed to cultivate the bacterium but he accidentally left a sample in his laboratory over the Easter holiday in 1982.

When he returned five days later, the bacterium, later denoted as Helicobacter pylori, had cultivated, said Nobel Assembly member Sten Grillner.

"It was kind of an accident," Grillner told The Associated Press. "But then many great discoveries are made by a combination of an accident and the prepared mind."

The two researchers then found that the organism "was present in almost all patients with gastric inflammation, duodenal ulcer or gastric ulcer," the assembly said.

Against Prevailing Knowledge

Warren told The Associated Press that it took a decade for others to accept their findings.

"For about a hundred years, or a thousand years, the standard teaching in medicine was that ... the stomach was sterile and nothing grew there because of corrosive gastric juices," he said. "So everybody believed there were no bacteria in the stomach."

"When I said they were there, no one believed it," he added.

Marshall is a researcher at the University of Western Australia in Nedlands, south of Perth. Warren retired in 1999 from a pathology position at the Royal Perth Hospital.

Nobel Assembly member Staffan Normark said the findings changed the way science looked at the causes of ulcers, and how to treat them.

"This was very much against prevailing knowledge and dogma because it was thought that peptic ulcer disease was the result of stress and lifestyle," Normark said at a news conference announcing the winners.

Everyday Benefits

Many other diseases, including Crohn's disease, ulcerative colitis, rheumatoid arthritis and atherosclerosis happen because of chronic inflammation, the assembly said in its citation, adding that the Australians' discovery stimulated the search for microbes as possible reasons for other inflammations.

"The work by Barry Marshall and Robin Warren produced one of the most radical and important changes in the last 50 years in the perception of a medical condition," said Lord May of Oxford, president of Britain's Royal Society.

"In 1985, Marshall showed by deliberately infecting himself with the bacterium Heliobacter pylori that it caused acute gastric illness," he said.

Today, it has been firmly established that Helicobacter pylori causes more than 90 percent of duodenal ulcers and up to 80 percent of gastric ulcers.

By the 1990s, a series of antibiotics had been produced that can completely cure ulcers, and prevent them from returning, Grillner said. Before Warren and Marshall's discovery, ulcers were often treated with surgery that removed part of the stomach.

"That is now absolutely unnecessary," Grillner said. "So the everyday benefits of this are rather substantial."

Coveted Award

The medicine prize is awarded by the Karolinska institute in Stockholm as stated in the will of Alfred Nobel, a Swedish industrialist who founded the prestigious awards in 1895.

The prize includes a check for 10 million kronor (€1 million; US$1.3 million), a diploma, gold medal and a handshake with the king of Sweden at the award ceremony in Stockholm on Dec. 10.

The coveted award honoring achievements in medical research opened this year's series of prize announcements. It will be followed by prizes for physics, chemistry, literature, peace and economics.

Previous Australian Nobel laureates include Patrick White, the author of "The Aunt's Story" and "The Tree of Man," who won the literature prize in 1973; John Warcup Cornforth who won the chemistry award in 1975; and medicine winners Sir Howard Walter Florey (1945), Sir Frank Macfarlane Burnet (1960), Sir John Carew Eccles (1963) and Peter C. Doherty (1996).