By Nathan Seppa, Peter Weiss and Aimee Cunningham
![](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2005/10/5331.jpg?resize=150%2C150&ssl=1)
Physiology or Medicine
Two Australian scientists who showed that bacteria can cause stomach ulcers have won the 2005 Nobel Prize for Physiology or Medicine.
The researchers made their discovery 23 years ago, at a time when ulcers were thought to result mainly from excess stomach acid brought on by stress and spicy food. In 1979, J. Robin Warren, a pathologist at the Royal Perth Hospital, noticed a curved bacterium in stomach-tissue samples from a patient. A few years later, a gastroenterologist at the hospital, Barry J. Marshall, cultured the microbe—ultimately named Helicobacter pylori. The two scientists then found H. pylori in nearly all patients with ulcers and also in most patients with gastritis, an inflammation of the stomach lining.