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 preventive tree-cutting which has a huge cost 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. Indeed, using a bacterium vector naturally present in the trees, our team offers an alternative solution originated from synthetic biology. Thanks to different genetic modules, the engineered bacterium called SubtiTree is first able to head towards the pathogen, then to bind to its cell wall in order to finally deliver different fungicides to save the tree from its invaders. Taking into account the ecological and ethical matters, our team thinks about how to limit the spreading of the optimized microorganism through different strategies. Although our project was born from a local problematic, it is transposable to other tree vascular diseases.

Choice of the chassis

Bacillus subtilis has been reported to be an endophytic bacterium of a large variety of plants and trees. 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 so as to fight Canker Stain from the inside of the tree. Injected directly in the tree sap, our smart bacterium will act as a curative and preventive drug.

Chemotaxis Show more

First, the bacterium targets the pathogen thanks to 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 by 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

To finish, our designed bacterium fights against the pathogen by setting up a powerful treatment based on the production of three different fungicides.

Spreading Show more

Our team worked on different aspects to keep control on SubtiTree. The aim is to prevent horizontal transfers between different bacteria and to contain the engineered bacterium inside the tree during one season.

Context project

Chemotaxis