Which bacterium is associated with stomach ulcers and was identified by Barry Marshall and Robin Warren?

Helicobacter pylori is the bacterium associated with stomach ulcers and identified by Barry Marshall and Robin Warren.

H. pylori colonizes the stomach lining, an environment once thought too acidic for bacteria to persist. Its urease enzyme helps it survive by producing ammonia that locally raises the pH around the cell. Persistent infection can cause chronic gastritis and is strongly linked to peptic ulcer disease.

Australian doctors Barry Marshall and Robin Warren reported the organism’s importance in the early 1980s. Their work overturned the older belief that ulcers were mainly caused by stress, spicy food, or excess acid alone. They received the 2005 Nobel Prize in Physiology or Medicine.

Treatment usually combines antibiotics with acid-suppressing medicine, although resistance patterns matter. H. pylori is not the same organism as the bacteria that commonly cause acute food poisoning, and many infected people have no symptoms.