Escherichia coli (commonly abbreviated E. coli; pronounced /ˌɛʃɨˈrɪkiə ˈkoʊlaɪ/, named after Theodor Escherich) is a Gram negative rod-shaped bacterium that is commonly found in the lower...
Because E. Coli is short for it's scientific name, Escherichia Coli. And you wouldn't want to have to say that constantly in science class, would you? :)