Biological Modules

The first question we had to face for the E.calculus project was the transposition of an electronic device into a reasonable biological system.
The diagram of an electronic full adder (see below) can be divided into three independant parts: Input and Output signals (A, B, C_in, S, C_out) and logic gates (XOR, AND, OR). The rationale for doing this classification was: logic gates can be universal but input and output signals must be adaptable for diverse applications and microorganisms.

Input

For the input, we needed a signal that could easily represents "ON" and "OFF" states. Light came as a natural solution because it is easily switchable to "ON" and "OFF" states and color can be varied to represent several inputs (A and B).

Output

The output needed to be a signal that can be easily seen without any complicated device or apparatus, something visual like the color of the organism bearing the full adder.

Carry

The carry (C_in and C_out), belongs to both the input and output modules. We thought of a molecule that could transmit a message from one colony to the other.

Logic Gates

An electronic full adder is composed of 5 logic gates. Transcriptionally regulated logic gates exist and have already been described. However, a major breakthrough in Synthetic Biology appeared during 2013 with two publications related to recombination-based logic gates. They inspired us and are the basis of our work.

Full Adder

The full adder is the integration of the signals (input, ouput, carry) with the logic gates. Its biological description can be found here.