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Scanning electron micrograph (SEM) of Photocomposite, E. coli on the surface of human skin and hair follicle. Human skin (epidermis) with hair emerging from hair follicle. Numerous desquamating cells are concentrically arranged around the base of the hair shaft. Escherichia coli is a Gram-negative, facultatively anaerobic, enteric, rod prokaryote. This bacterium is normally a part of the human and animal microbiota. Most E. coli strains are harmless, but some strains can cause serious problems such as: food poisoning, urinary tract infections, traveller's diarrhoea and nosocomial infections. The E. coli 0157:H7 strain is fatal to humans if contracted when contaminated meat is cooked inadequately. Magnification: bacteria x 800; follicle x260 when shortest axis printed at 25 millimetres. (KEYSTONE/SCIENCE PHOTO LIBRARY/DENNIS KUNKEL MICROSCOPY/SCIENCE PHOTO LIBRARY)