Escherichia coli, E. coli, in short, is a rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms.
Figure 1: Colored scanning electron micrograph of E. coli cells.
Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in their hosts, and are occasionally responsible for product recalls due to food contamination. The harmless strains are part of the normal flora of the gut, and can benefit their hosts by producing vitamin K2, and prevent colonization of the intestine with pathogenic bacteria.
E. coli can be grown and cultured easily and inexpensively in a laboratory setting. This makes it one of the best-studied model organisms. E. coli is also an important species in the fields of biotechnology and microbiology, where it has served as the host organism for the majority of work with recombinant DNA. Under favorable conditions it's generation time is only 20 minutes.