Escherichia coli, commonly known as E. coli, is a bacteria that colonizes the intestines of humans and animals, and most types of it are harmless, according to the Centers for Disease Control. There are over 700 types of E. coli, notes Todar's Online Textbook of Bacteriology.
E. coli was first described in 1885 and is part of the Enterobacteriaceae family, explains Todar's Online Textbook of Bacteriology. It is a Gram-negative rod that survives with or without oxygen, depending on its environment. Generally, E. coli is able to use glucose for all metabolic processes. The bacteria may use flagella to propel movement or fimbriae to adhere.
E. coli types are categorized by O, H and K antigens in addition to unique virulence factors such as toxins. The bacteria may also have a variety of drug-resistant characteristics, such as a thick outer capsule. Pathogenic E. coli may cause urinary tract infections, neonatal meningitis and gastroenteritis in humans.