<unk>  (), also known as<unk>  (), is a Gram-negative, facultative anaerobic, rod-shaped,<unk> form bacterium of the genus<unk>  that is commonly found in the lower intestine of warm-blooded organisms. Most<unk>  strains are harmless, but some serotypes (EPEC, ETEC etc.) can cause serious food poisoning in their hosts, and are occasionally responsible for food contamination incidents that prompt product recalls. The harmless strains are part of the normal microbiota of the gut, and can benefit their hosts by producing vitamin K2, and preventing colonisation of the intestine with pathogenic bacteria, having a mutualistic relationship.<unk>  is expelled into the environment within fecal matter. The bacterium grows massively in fresh fecal matter under aerobic conditions for three days, but its numbers decline slowly afterwards.<unk>  and other facultative anaerobes constitute about 0.1% of gut microbiota, and fecal–oral transmission is the major route through which pathogenic strains of the bacterium cause disease. Cells are able to survive outside the body for a limited amount of time, which makes them potential indicator organisms to test environmental samples for fecal contamination. A growing body of research, though, has examined environmentally persistent<unk>  which can survive for many days and grow outside a host. The bacterium can be grown and cultured easily and inexpensively in a laboratory setting, and has been intensively investigated for over 60 years.<unk>  is a chemoheterotroph whose chemically defined medium must include a source of carbon and energy.<unk>  is the most widely studied prokaryotic model organism, and an important species in the fields of biotechnology and microbiology, where it has served as the host organism for the majority of work with recombinant DNA. Under favorable conditions, it takes as little as 20 minutes to reproduce.
Escherichia coli
Salmonella
Enterobacter cloacae
Helicobacter
Vibrio cholerae
Entamoeba coli
Citrobacter koseri
Salmonella enterica subsp. enterica