Gut bacterium. Coloured transmission electron micrograph (TEM) of a bacterium from the family Enterobacteriaceae. This family comprises Gram- negative rod-shaped bacteria, most of which have flagellae (hair-like 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: x27,200 when printed 10 centimetres wide.