E. coli bacteria (image 6 of 14). Light micro- graph of 25 Escherichia coli (or E. coli) bacteria, growing on an agar plate at 25 degrees Celsius. These rod-shaped, gram-negative bacteria are found in the intestines of humans & animals. While E. coli is usually harmless, under certain conditions it may increase in number and cause infection. Certain E. coli types are responsible for gastroenteritis, diarrhoea & other urinary tract infections. A temperature increase of about 10 degrees Celsius will double this E. coli colony's growth rate. Magnification: x2000 at 35mm size. See images B230/171 to B230/184 for the growth of the colony in 40 minute stages.