Escherichia coli (molecular biology)

Escherichia coli (/ˌɛʃᵻˈrɪkiə ˈkoʊlaɪ/; commonly abbreviated E. coli) is a Gram-negative gammaproteobacterium commonly found in the lower intestine of warm-blooded organisms (endotherms). The descendants of two isolates, K-12 and B strain, are used routinely in molecular biology as both a tool and a model organism.

Escherichia coli is one of the most diverse bacterial species with several pathogenic strains with different symptoms and with only 20% of the genome common to all strains. Furthermore, from the evolutionary point of view, the members of genus Shigella (dysenteriae, flexneri, boydii, sonnei) are actually E. coli strains "in disguise" (i.e. E. coli is paraphyletic to the genus).

In 1885, Theodor Escherich, a German pediatrician, first discovered this species in the feces of healthly individuals and called it Bacterium coli commune due to the fact it is found in the colon and early classifications of Prokaryotes placed these in a handful of genera based on their shape and motility (at that time Ernst Haeckel's classification of Bacteria in the kingdom Monera was in place).

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