Transmission Electron Micrograph (TEM) of Escherichia coli. Escherichia coli, commonly known as E. coli is part of the normal fauna of the gut in humans and animals. E.coli may give rise to infection under certain conditions. Serotypes of E. coli are responsible for gastroenteritis in children, particularly in tropical countries. In adults it is the cause of "traveler's diarrhea", and the majority of urinary tract infections.