Coloured timelapse microscope footage of Escherichia coli bacteria multiplying in culture. Each bacterium can divide every 20-30 minutes in optimum conditions. E. coli is a Gram-negative bacillus that is found as part of the healthy flora in the human large intestine, although some strains can be pathogenic. E. coli can also be cultured easily in the laboratory, which has led to its widespread use as a model organism in biological research. Each cell measures around 2x0.5 microns. This footage has been speeded up 440 times.