Barry James Marshall , AC , FRS , FAA ( born 30 September 1951 ) is an Australian doctor and winner of the 2005 Nobel Prize in Physiology or Medicine . He is Professor of Clinical Microbiology at the University of Western Australia . 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 .