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From 2014.igem.org

Pattern Formation

We want to form a pattern (a motif) on a grid of bacterial colonies. Our output signal is binary: a bacterial colony is either in an on-state or in an off-state. The on-state can be read out by the green fluorescence.

Each bacterial colony has two parents. Those parents emit a signal, if they are on. The bacterial colony can differentiate the two signals it gets from its parent. Depending on theignals received by a bacterial colony, it will switch on or off. This is the principle of a logic gate.

In our project, we are using a particular logic gate, named XOR. Here is an example : imagine your bacterial colonies are either happy or unhappy. If they are happy, they send a signal to their children, inviting them to a party. If a colony is invited to one party (by either of its parents), it becomes happy. If it is not invited to any party, it is unhappy. If a colony is invited by both its parents, it becomes unhappy (because there is here a dilemma).