Barry James Marshall is an Australian physician, Nobel Laureate in Physiology or Medicine, Professor of Clinical Microbiology and Co-Director of the Marshall Centre at the University of Western Australia. Marshall and Robin Warren showed that the bacterium Helicobacter pylori plays a major role in causing many peptic ulcers, challenging decades of medical doctrine holding that ulcers were caused primarily by stress, spicy foods, and too much acid. This discovery has allowed for a breakthrough in understanding a causative link between Helicobacter pylori infection and stomach cancer. The Nobel Prize in Physiology or Medicine 2005, announced October 3, 2005. Barry J. Marshall and J. Robin Warren, “for their discovery of the bacterium <i>Helicobacter pylori</i> and its role in gastritis and peptic ulcer disease”. Barry J. Marshall: born 1951, Kalgoorlie, Australia. J. Robin Warren: born 1937, Adelaide, Australia. Wiki link Wiki link Data: the Nobel Foundation (CC0).