Gut bacterium reproducing Coloured transmission electron micrograph TEM of a single bacterium dividing into two identical clone daughter bacteria Under optimal conditions some bacteria can grow and divide extremely rapidly and bacterial populations can double as quickly as every minutes This bacterium is a member of the family Enterobacteriaceae which comprises Gramnegative rodshaped bacteria that often have flagellae hairlike strands that are used for movement Many are a normal part of the gut flora found in the intestines but some are pathogenic such as Salmonella enterica and certain strains of Escherichia coli and can cause foodborne illnesses Magnification x when printed centimetres wide