Salmonella bacterium. Coloured transmission electron micrograph (TEM) of a single Salmonella enteritidis bacterium. This Gram-negative rod- shaped bacillus causes food poisoning (Salmonello- sis) in humans. Hair-like flagellae are used for motility. Salmonella enteritidis produces entero- toxins which act on the small intestine. Infection occurs when numbers of these bacteria are ingested in contaminated food, particularly meat, milk and chicken eggs. Typical Salmonella food poisoning occurs with symptoms including vomiting, nausea, abdominal pain and diarrhoea. The infection is usually controllable and is rarely fatal. Magnification x13,000 at 6x7cm size.