Campylobacter jejuni is a microaerophilic, Gram-negative, human pathogen that is the major cause of bacterial food-borne diarrhoea (gastroenteritis). It is most frequently responsible for a form of post-infection neuromuscular paralysis known as Guillain Barre' syndrome. It also leads to an immunoproliferative small intestine disease that is a rare malignant lymphoma of the intestine. Motility is essential for pathogenicity.