The family Enterobacteriaceae is a large group of Gram-negative, non-spore-forming bacteria that includes many of the more familiar pathogens, such as Salmonella, Escherichia coli (E. coli), Yersinia pestis, Klebsiella and others. They are facultative anaerobes, meaning they can survive in both oxygen-rich and oxygen-poor environments, and most can reduce nitrate to nitrite. Many species have flagella and are therefore mobile. They are a normal part of the gut flora found in the intestines of humans and animals. Some types can cause disease in the host organism.
