False-colour transmission electron micrograph of the bacteria Salmonella typhimurium in the early stages of division. A Gram-negative flagellate. S. typhimurium is a major cause of food poisoning (salmonellosis) in humans. Salmonella bacteria are transmitted in food. Infections are common in poultry & eggs. Inadequately cooked pork & beef are also potential sources. Oysters farmed near sewage outlets may become contaminated with faecal bacteria. Rats & mice are also common carriers. Clinical symptoms are headache, fever, abdominal pain & diarrhoea. Magnification: x12,500 at 35mm size.