© Top: Wikimedia Commons, Public Domain. Author: Timreid, 26 February 2007. Center and bottom: Reprinted by permission from Macmillan Publishers Ltd: Nature 403, 335-338 (20 January 2000).
The represillator is a simple synthetic biological network developed by Michael Elowitz and Stanislas Leibler. The network induces E. coli cells to periodically produce green fluorescent protein that can be observed under a microscope. It consists of three genes in a feedback loop, each of which represses the other genes, leading to oscillatory gene expression over time. The top image shows the equivalent circuit diagram for the repressilator. The center photographs show the total population of cells (bottom) compared to the green fluorescent portion of the population (top). The plot shows the total amount of green fluorescence over time: an oscillation superimposed on a general upward trend that matches population growth. (Unit: 9)