Musings of a Political Scientist

Escherichia coli

EColi by Bryan Brandenburg

Escherichia Coli (E Coli)

Escherichia coli, usually abbreviated to E. coli, (coli is latin for “of the colon”) discovered by Theodor Escherich, a German pediatrician and bacteriologist, is one of the main species of bacteria that live in the lower intestines of mammals, known as gut flora. Specimens have also been located on the edge of hot springs. According to US Department of Health and Human Services Centers for Disease Control and Prevention, the E. coli strain O157:H7, one of hundreds of strains of the bacterium E. coli, causes illness in humans. Presence in surface water is a common indicator of fecal contamination. It belongs among the Enterobacteriaceae, and is commonly used as a model organism for bacteria in general. One of the root words of the family’s scientific name, “enteric”, refers to the intestine, and is often used synonymously with “fecal”.

The number of individual E. coli bacteria in the feces that a human excretes in one day averages between 100 billion and 10 trillion. All the different kinds of fecal coli bacteria, and all the very similar bacteria that live in the ground (in soil or decaying plants, of which the most common is Enterobacter aerogenes), are grouped together under the name coliform bacteria. Technically, the “coliform group” is defined to be all the aerobic and facultative anaerobic, non-spore-forming, Gram-negative, rod-shaped bacteria that ferment lactose with the production of gas within 48 hours at 35 °C (95 °F). In the body, this gas is released as flatulence. E. coli cells are elongated, 1–2 µm in length and 0.1–0.5 µm in diameter.

As Gram-negative organisms, coli are unable to sporulate. Thus, treatments which kill all active bacteria, such as Pasteurization or simply boiling, are effective for their eradication, without requiring the more rigorous sterilization which also deactivates spores.

As part of their adaptation to mammalian intestines, coli grow best at the higher temperatures characteristic of such an environment, rather than the cooler temperatures found in the soil or other environment.

See also: Bacteriophage – PHI X 174