Escherichia coli, more commonly known by the abbreviated moniker of E. coli, is a Gram-negative, rod-shaped bacterium commonly found in the lower intestines of warm-blooded animals, including humans.
In this electron micrograph from Thomas Deerinck at UC San Diego’s National Center for Microscopy and Imaging Research, the bacterium is falsely colored in happy hues. And, in fact, most strains of E. coli are harmless, making up an estimated 0.1 percent of gut flora without generally making a peep. It’s thought the microbes earn their intestinal keep by producing vitamin K2 for the host and helping prevent the establishment of pathogenic bacteria.
Some E. coli strains, however, can cause serious gastrointestinal distress. They are a major culprit in cases of food poisoning and occasionally responsible for significant product recalls.
Typically, E. coli bacteria cells survive for only a limited time outside the body, which makes them a good, timely indicator of fecal contamination in the environment (such as sewage spills at beaches). There is growing evidence, however, that some strains are evolving the ability to persist outside hosts for longer periods of time.
Not surprisingly, the bacterium grows quickly and easily. It’s been a cheap, tried-and-true laboratory model for more than 60 years.