Color enhanced Transmission Electron Micrograph (TEM) of Escherichia coli (E. coli) O157:H7 showing flagella (pseudoreplica technique). The bacterium is a known cause of foodborne illness. The strain of E. coli, O157:H7, was first recognized in 1982 during an outbreak of severe diarrhea that was caused by contaminated hamburgers. Infection can be prevented by making sure that meat is cooked thoroughly. Escherichia coli is a gram-negative, facultatively anaerobic, rod-shaped, coliform bacterium of the genus Escherichia that is commonly found in the lower intestine of warm-blooded organisms (endotherms). Magnification: unknown.