An Electronic Analogous Synthetic Genetic 2-to-4 Digital Decoder and Associated Molecular Tools in Living Cell

Adapting engineering design principle in the realm of molecular cell biology, synthetic biologists developed few artificial cellular information-processing systems in recent years. Those systems can process extracellular chemical signal to count, to communicate and to show different patterns in response. One of the further challenges is to develop novel system that can process multiple extracellular chemical signals together and decode different combination of signals to make distinct decision for each and every possible combination. Here we demonstrate our recent effort in creating a population level 2-to-4 genetic decoder using synthetic gene circuits in living Escherichia coli by following digital electronics principle. A 2-to-4 decoder has two input signals and based on the combination of inputs, the device can take four distinct decisions. Here we have designed and constructed a set of synthetic genetic AND, NOR, AND (NOT) and (NOT) AND gates by creating a library of novel hybrid promoters and novel truncated proteins with non-conventional start codon and characterized them experimentally. The best candidates with digital behavior have been taken for full circuit assembly. However, assembling several genetic cascades in a single plasmid is a challenge. Here we developed a modified BIOBRICK assembly technique, where multiple genetic cascades can be assembled in a single plasmid in any direction, a characteristic lacked in previous systems. In our system we have two extra cellular chemicals as input signals and 4 different fluorescent proteins as distinct outputs. Such systems have potential application in artificial cellular communication systems, cellular robotics and programmed therapeutics.