Genetically-altered bacteria. Coloured Trans- mission Electron Micrograph (TEM) of Escherichia coli bacteria which have been genetically engin- eered to produce human insulin. Diabetics need insulin to control their blood sugar level. The bacteria are mostly magenta, whilst their insulin- production sites are orange. E. coli is a normal inhabitant of the human gut. Genetic material can be inserted into E. coli using viruses or special strands (plasmids) of genetic material. The new genes alter the behaviour of the bacteria, and are passed on to their offspring. The bacteria are raised in a culture and pure insulin is extracted from them. Magnification: x4000 at 35mm size.