Team:INSA Toulouse

Abstract, let's count with ''E. Calculus''

Transposition of Boolean operators into genetic devices is one of the various goals of Synthetic Biology. The common problem with genetic Boolean operators is their inherent inability to make a clear difference between the 0 and 1 state. A new way to build one-way logical gates using Serine recombinases will be implemented, taking advantage of specific recombination sites to avoid the reversibility of recombination. Furthermore, we will also implement a strong genetic switch to avoid transcriptional background and this will lead to a perfectly controlled transcription of the recombinases. These systems should approach as much as possible a two digit device and help setting strong and robust genetic logical gates. To demonstrate the validity of these two state logic gates, we will create a n-bits full-adder using recombinase-based AND and XOR logical gates. The E. calculus strain should be able to execute full n-bits counting, taking in account the carry at each stage.
Irreversibility of recombination allows us to get great signal amplification (devices should be transmitted to next generation), with only two possible states. The general idea of those kinds of genetic logical gates is the use of genetics elements placed in different ways (forward or reverse) between specific recombinational sites. Expression or not of recombinase (input signals) should induce change (or not) state of the gate, which allow us to get an answer (output signal). We also try to link different gates between them, aiming finally to construct a full adder. We know that recombinases are actives at even in low concentration in cell (3 or 4 recombinases are enough to operate recombination). We have to control strenghtly recombinases expression. We choose traductional control with use of fresh-designed riboswitches, avoiding this way probables leaks of a transcriptional control.