Original: Barry James Marshall , AC , FRS , FAA ( born 30 September 1951 ) is an Australian physician , Nobel Prize laureate in Physiology or Medicine , and Professor of Clinical Microbiology at the University of Western Australia .
Simplified: In 2005 , the Karolinska Institute in Stockholm gave the Nobel Prize in Physiology or Medicine to Dr. Marshall and Dr. Warren for finding the bacterium Helicobacter pylori and its part in gastritis and peptic ulcer disease .