| 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. |
