Petri dish culture of colonies of Escherichia coli, a species of motile, rod-shaped, gram negative bacteria found as part of the normal fauna in the human gut. On the lower half of the dish, the colonies have been streaked, on the upper half they have been used to write the name of the bacterium. Under certain conditions E.coli may become pathogenic causing infection to the urinogenital tract & diarrhoea in children. E. coli has played an important role in genetic engineering and the emergence of the biotechnology industry. A large amount of experimental work on genetic manipulation was performed using DNA from E. coli.