Escherichia coli is an Enterobactericeae bacteria. This family name is derived from the fact that nearly all species in it, more or less, constantly inhabit the intestines of humans and animals. Because of its widespread presence in the environment and its ability to promote disease in humans, one of the most prominent members of this family is the species Escherichia coli. This bacterium is so common that its name has come to describe all similar bacteria as "coliform" or coli-like.
These enterobacteria are gram-negative, nonspore-forming straight rods, aerobic and facultative anaerobes, ranging from 1 to 2 mm in diameter and are from 3 to 10 mm in length. All species ferment glucose, which allows for a testing method known as "presumptive E. coli," and all microscopically, are indistinguishable. …
