Discovered in the human colon in 1885 by German bacteriologist Theodor Escherich, the bacterium Escherichia coli, E. coli for short, is magnified 30,000 times in this transmission electron micrograph. The small, fine hairs help it to stick to the cells of the intestine, while its long whip-like flagella propel it along in search of food. Most strains of Escheria coli are harmless - millions live naturally in our digestive system where they synthesize vitamins, suppress more harmful bacteria and aid digestion. Some strains, however, can cause urinary tract infections and food poisoning, which can be fatal.