Unidentified curved bacilli on gastric epithelium in active chronic gastritis.

In 2005 Marshall and Warren shared the Nobel prize in Physiology or Medicine "for their discovery of the bacterium Helicobacter pylori and its role in gastritis and peptic ulcer disease."

See also their follow-up paper published in 1984: "Unidentified curved bacilli in the stomach of patients with gastritis and peptic ulceration", Lancet, 323 (8390) 1311-15, 1984.