A synthetic gene network that counts

Synthetic gene networks can be constructed to emulate digital circuits and devices, giving one the ability to program and design cells with some of the principles of modern computing. A counter is one such device that would enable a new type of memory and allow for complex synthetic programming and novel behaviors. Here we report a synthetic genetic counter in Escherchia coli that counts up to three identical induction events, expressing a unique protein species to signify each number. The counter is comprised of a transcriptional cascade in which transcription is de-coupled from translation by riboregulators. The modularity of this device permits counting of varied user-defined inputs and its open-ended architecture provides a potent biotechnology platform for counting higher numbers, which is supported by mathematical modeling.