False-colour scanning electron micrograph (SEM) of a colony of Staphylococcus aureus, a species of spherical, Gram-positive, non-motile bacteria. Many species of Staphylococcus cause disease in man through secretion of exotoxins: S. aureus is commonly present on skin & mucous membranes & causes boils & internal abscesses, and is the commonest cause of pyogenic (pus-forming) infections in man. Other species produce toxins causing food poisoning. Staphylococcal enteritis, which is severe & potentially fatal, results from use of broad-spectrum antibiotics which allows S. aureus to proliferate in the intestines. Magnification: x3,000 at 35mm size.