Campylobacter jejuni (Cj) is the leading cause of bacterial food poisoning in the world. Each year about 300,000 Canadians are infected by these highly invasive bacteria through ingestion of undercooked meats or dairy products. An acute infection causes diarrhea, fever, vomiting, and, occasionally, death. Cj infection may also lead to Guillain-Barré Syndrome, an autoimmune disease that causes weakness or tingling in the legs and arms. In some cases, symptoms can become so severe that the patient is almost totally paralyzed. Most people recover, although some continue to have some degree of weakness. Ann Lin is researching how Cj bacteria cause disease in the gastrointestinal tract. Cj is predominantly found in the first and last sections of the small intestine and the colon. The bacteria penetrate layers of cells in the intestine and infect underlying tissues. Lin is examining whether this process disrupts the intercellular junctions that provide integrity for host epithelial cells. Disrupting this barrier is believed to contribute to diarrhea, but the molecular process is not well understood. Lin will determine whether Cj causes gastrointestinal disease by damaging the barrier. Ultimately, her findings could lead to the development of new methods of preventing Cj infection.