A common bacterium used in laboratory tests to assess antimicrobial effects.Escherichia coli (E. coli) is a rod-shaped bacterium that naturally lives in the lower intestine of warm-blooded organisms, including humans. Most strains are harmless and even beneficial, aiding in digestion and producing essential vitamins. However, certain strains, such as O157:H7, can cause severe food poisoning. In science, E. coli is the workhorse of microbiology and molecular biology, serving as the standard model organism for studying bacterial genetics, metabolism, and the effects of antimicrobial agents.
E. coli was first described in 1885 by the German pediatrician Theodor Escherich, who isolated it from the feces of healthy infants. It was initially named Bacterium coli commune and later renamed in honor of its discoverer.
E. coli grows rapidly in simple laboratory media, doubling in number every 20 minutes under optimal conditions. Its genetic material is easily manipulated, allowing researchers to insert, delete, or modify genes with precision. For antimicrobial testing, a culture of E. coli is exposed to a candidate substance, and the inhibition of bacterial growth is measured—either by observing clear zones on agar plates or by tracking optical density in liquid cultures. Its well-characterized biology makes it a reliable and reproducible system for such assays.
E. coli is used extensively in biotechnology to produce recombinant proteins, including human insulin and vaccines, and in laboratories worldwide as a standard organism for testing antibiotic efficacy and disinfectant safety.
A single E. coli cell contains about 4,000 genes, but only a fraction are essential for survival—under ideal conditions, it can lose over 90% of its genome and still grow.





