Novel Approaches

Artificial regulation networks

Metabolic engineering, one of the branch of Synthetic Biology, consists of producing molecules via biosynthesis, either from assembling existing, natural pathways or via the design of completely artificial metabolic paths. For both natural and artificial pathways, there exist a clear advantage to design genetic logic gates capable of perfectly controlled decisions at the cellular level. The recombination-based genetic logic gates have the capability to permanently switch the state of the gate and therefore is not sensitive to metabolic variations, to retrocontrolled transcriptionnal induction or repression or to changes in metabolic induced changes in enzyme activities.

Complex tree decision in cells

Natural metabolic regulation is by essence homeostatic. For example: the regulation of a natural metabolite operates through constant variation (usually very small) around an average value, and the gene regulation works the same way. Building an artificial and complex network of metabolic paths requires that some of the decisions and orientations of the recreated metabolism are controlled by the engineer and not by the cell. Logic gates such as AND, OR, XOR, NOR etc. are perfectly fit to do this kind of user controlled decision tree.

A simple example (to finish convincing you!!)

A brewer would like to ferment aromatized beer with mint taste. The pathway for producing menthol was introduced in yeast, but is highly toxic for the cells. Hence, the production should occur only after fermentation (when the beer is at 6% alcohol). Furthermore, two essentials metabolites (A and B) will be used for producing menthol. This can be translated as a triple AND door like in the following scheme.