Essencia Coli

Schematic illustration of the setup for controlling concetration of molecule 'X'

The main idea is to synthesize a molecule 'X' and at the same time measure the concentration of this molecule outside the cell in order to keep the concentration constant. This concentration can then be modulated using light intensity. This creates a controll system with feedback from the outside concentration of molecule 'X'.

For proof of concept the molecule 'X' is set to be vanillin, in principle this can be any molecule as long as it can be synthesized and a receptor is available. The light receptor will activate transcription of A on irradiation of blue light which should stimulate synthesis of Vanillin. The concentration vanillin outside the cell is measured with a vanillin receptor this will result in transcription of B and will block the actions of A. The activation of synthesis by A and the inhibition by B is done by a key/lock setup. The translation of the Vanillin synthesizing proteins need a key in order to translate, A will provide the key. Therefore upon irradiation of blue light the required proteins will be translated. B, however, will be an anti-sense mRNA of A, blocking the actions of the key. Thus if the concentration of vanillin increases the synthesis of vanillin-synthesizing proteins will decrease untill it stops completely.

The complete setup with the corresponding biobricks can be seen on below