Team:Toulouse/Project/Overviews

Among many other things, Southern France is well-known for the gorgeousness of its landscapes. Plane trees (Platanus sp.) are widely present and participate to the charm of this area, especially along the famous “Canal du Midi”. It is impossible to imagine this UNESCO World Heritage masterpiece without its trees. Unfortunately, these trees are threatened by a severe fungal infection called Canker Stain, and today the only treatment consists in a costly preventive tree-cutting and implies significant ecological troubles.

Facing this emergency, the students from the iGEM Toulouse Team decided to be committed to the protection of their local heritage. Using a bacterium vector naturally present in the trees, our team offers an alternative solution originated from synthetic biology. Using different genetic modules, we engineered a bacterium (SubtiTree) capable of heading towards the pathogen, binding to its cell wall and finally delivering different fungicides to save the tree from its invaders. Our team also began to design genetic modules preventing any accidental spreading of the optimized microorganism, thus limiting the ecological and ethical footprints of SubtiTree. Although our project originated from a very local and specific tree disease, it could be transposable to other plant diseases.

Choice of the chassis

Bacillus subtilis has been reported to be an endophyte bacterium of a large variety of plants and trees. Therefore, this model organism is a perfect chassis for our project. Already used to treat plant diseases and fungal pathogens, we aim to engineer Bacillus subtilis to fight Canker Stain inside of the tree. Injected directly in the tree sap, our smart bacterium will act as a curative and preventive drug.

Figure 1: Schema of our general strategy

Chemotaxis Show more

First, the bacterium targets the pathogen with a chemotaxis module which recognizes the soluble molecules released by the fungus' cell wall (N-acetylglucosamine).

Binding Show more

Then, SubtiTree binds onto the pathogen using a chimeric protein anchored to the bacterium peptidoglycan and which can make a bridge between bacterial cell wall and fungal chitin, the main component of the pathogen's cell wall.

Fungicides Show more

In the third step, our designed bacterium fights the pathogen by production of a powerful treatment based on the release of three different fungicides.

Spreading Show more

Our team worked on different aspects to control SubtiTree released in the environment. The aim is to prevent horizontal transfers between different bacteria and limit the growth and survival of the engineered bacterium inside the tree during one season.

Context project

Chemotaxis