a species of Gram-negative bacteria normally present in the intestines of all vertebrates and widely used in biological research: its presence in water in certain quantities indicates fecal pollution that can cause diarrhea
See E. coli in American Heritage Dictionary 4
(ē kōˈlī)
noun
A bacillus (Escherichia coli) normally found in the human gastrointestinal tract and existing as numerous strains, some of which are responsible for diarrheal diseases. Other strains have been used experimentally in molecular biology.