Synthetic Genetic Devices for Higher-Order Artificial Signal Processing and Computation in Living Cells

Biology is a complex arena that involves a multitude of inputs and outputs occurring at the right levels, time and combination to achieve the fine tuning called life. These interaction networks implement robust genetic circuitries created over time. Today, Synthetic Biology demands Synthetic Genetic networks that can function involving larger sets of inputs and outputs and perform more complex decision-making regimes. Despite the plethora of synthetic circuits already designed, we are still far behind the genetic complexity of nature and thus far from attaining the full potential of engineering genomes and cellular robotics. Towards this, we have been trying to develop a few complex genetic computational circuits- namely a biological 1-2 multiplexer (input selector) and a 2-1 de-multiplexer (output selector) amongst others- conceived from electronic circuit design principles. Attaining desired regulation through external chemical inducers, transcription factors and translational control, these circuits have required designing and characterizing libraries of synthetic Promoters and RBS's. Fine tuning of the transcriptional- translational regulatory machinery has culminated in satisfactory Boolean response. Furthermore, we have also explored ­ how minimalistically can one increase the input-output complexities of a synthetic gene circuit through developing a 3 input-3 output combinatorial genetic system. It orthogonally senses three small molecule signals as inputs and responds through three fluorescent proteins in accordance with input logical states. Consensus of the Mathematical models and experimental validations of the systems show good predictability. These circuits may be integrated in future into larger circuits and are stepping stones to more complex application-oriented genetic networks.