Team:Grenoble/Projet/Intro

Introduction :

With industries growth, wastes are accumulating and presence of pollutant and toxic products is becoming an international concern.

Our project is oriented in this problematic, Mercuro-Coli is a mercury biosensor which allows to detect and quantify mercury contained into polluted water. Intended to fieldwork studies, the device should be very easy to used :

• Ideally, the device should be a plate carried into a packaging.
• Once unpacked, the sample just has to be added.
• Finally, the result would be given by a red strip : its presence testifying that the sample contains mercury and its position on the plate acquainting about the quantity.

Specifications :

At the beginning of the project, specifications were defined about the final device. To get a better understanding on how the device should run, those are going to be taken back step by step.

• Operating living cell : E. Coli: BW 25 113
• Only one type of bacteria :

Once our genetic circuit achieved, it will be introduce to our E. Coli strain. Newly obtained bacteria strain will be then spread on the plate forming a bacteria film on the top of it.

• Comparative measure :

The comparative measure will be made by comparing mercury concentration to IPTG concentration. IPTG concentration will is the reference. So, an IPTG gradient concentration will be made beforehand constituting our scale of quantification.

By adding uniformly the polluted sample, two different bacteria behaviors will come up depending on the predominant concentration :

On the left side, where the mercury concentration is the uppermost, bacteria with a secretory behavior will appear. They have the ability to release in the external medium AHL molecules thanks to the expression of CinI protein. On the right, where the IPTG concentration is the uppermost, bacteria with a receiving behavior will come up. They express internal protein CinR able to receive AHL molecules.

So, we will have the emergence of two distinctive areas separated by one boundary that can move from one side to the other depending on the quantity of mercury. For example, if the sample contains less mercury the boundary will move to the left.

So, an IPTG gradient concentration will be made beforehand constituting our scale of quantification.

• A visual result :

The two different behaviors were chosen in purpose.

At the boundary, AHL molecule released by secreting bacteria will be received by the front of receiving bacteria. The complex formed by AHL molecule and CinR protein will then induce the coloration of the front receiving bacteria.

Let's go further to understand how such evolution of this system is possible with only one strain ?