Modelling

AHL diffusion in LB agar medium

To build a binary full adder our system must be able to communicate if necessary a carry. We chose to use a molecule, 3-oxohexanoyl-homoserine lactone (AHL). The AHL is a messenger in our system.

Different systems can be devised to implement the expression and diffusion of the AHL.

The system of Figure 1 operates as follows:
A petri dish containing colonies, which are equidistant from each other. The lights provide information on addition to perform, and the expression and the diffusion of AHL from one colony to another allows the carry propagation.

This system is quite simple but nevertheless raises a certain number of problems:

Production of AHL

To overcome the problem of the amount of AHL required for rapid diffusion of the messenger, we can well imagine a system in which liquid precultures may be deposited. So we get a higher cell density and a greater production of AHL.

Inoculation of cultures

The gradual inoculation of wells during the addition allows, first, to the AHL to diffuse into the medium, and second, not to fall in cell death.

The ideal distance between well

In order to find the ideal distance between two colonies we have searched a model which allow us to know: how does AHL diffuse into the medium and how many time the diffusion need to pass one colony to another.

One dimension model:
To overcome the problem of the amount of AHL required for rapid diffusion of the messenger, we can well imagine a system in which liquid precultures may be deposited. So we get a higher cell density and a greater production of AHL.