E. coli bacterium. Colored transmission electron micrograph (TEM) of an Escherichia coli bacterium from a urinary tract infection. This rod-shaped (bacillus) Gram-negative bacterium moves using its hair-like flagellae. It is an enterobacter, a normal and usually harmless inhabitant of the human intestine. Under certain conditions however, it may increase in number and cause infection. Types of E. coli are responsible for gastroenteritis in children, particularly in tropical countries. In adults it is the cause of 'travellers' diarrhoea' and of the majority of urinary tract infections. Magnification: x5,500 at 5x7cm, x2750 at 35mm size.