An Australian scientist who has won the 2005 Nobel prize for medicine has said his discovery was "bloody obvious".
Robin Warren and Barry Marshall's work on ulcers was pioneering
Robin Warren, who shares the prize with his colleague Barry Marshall, said he was "thrilled" to be recognised, but had always believed in their work.
The two scientists have described how they were initially shunned for insisting stomach ulcers were caused by a bacterium, not stress.
Dr Marshall finally swallowed the bacterium himself to prove his point.
The pair, who no longer live in the same part of Australia, were actually having a rare dinner together when they received the call from the Nobel committee telling them they had won.
Professor Warren said he was a "little overcome" by the award.
"It is nice to be officially recognised and it gives some sort of a stamp of approval, but we believed it within a few months because it was so bloody obvious," he told reporters.
Dr Marshall said he was shocked.
"I thought it was a new and exciting discovery but I did not believe it was the type of discovery that one got the Nobel prize for," the researcher at the University of Western Australia in Nedlands, Perth, said.
H. pylori is found in the stomach of about 50% of all humans
In developing countries almost everyone is infected
Infection is typically contracted in early childhood, and the bacteria may remain in the stomach for life
In most people there are no symptoms
However, it can trigger ulcers in 10-15% of those infected
The two men made their discovery in the early 1980s, but it took a long time to convince the medical community, who viewed them as eccentric.
"The idea of stress and things like that [as the cause of ulcers] was just so entrenched nobody could really believe that it was a bacteria," Dr Marshall told the Associated Press.
"It had to come from some weird place like Perth, Western Australia, because I think nobody else would have even considered it," he said.
Professor Warren is retired from a pathology position at the Royal Perth Hospital.
Dr Marshall, whom his wife describes as having a "dreadful sense of humour", eventually swallowed Heliobacter pylori, the bacterium they believed responsible for stomach ulcers, and became very ill.
Thanks to the their work, stomach and intestinal ulcers are often no longer a long-term, frequently disabling problem.
They can now be cured with a short-term course of drugs and antibiotics.
It is now firmly established that the bacterium causes more than 90% of duodenal (intestinal) ulcers and up to 80% of gastric (stomach) ulcers.