Potential solution

Our goal and its advantages
Our project goal is to degrade the most abundant microplastics present in the Mediterranean sea, namely polyethylene, polystyrene and polypropylene found in our everyday waste. This project found its origin in the desire to protect the marine ecosystem from human pollution by reducing the amount of microplastics in the sea and therefore protecting marine biodiversity and our health. The project, if it works, can become a solution for several problems, in France but also in the world. In France, it can reduce the amount of microplastics of the Mediterranean, one of the most polluted seas. The project can also be reengineered to be applied all over the world depending on the type of plastic that is mostly found ; that way the plastic pollution of all of the oceans, seas, rivers etc can be reduced.

In order to implement our project in real life some points needs to be addressed :

• Which “receiving” bacteria could be used ?
• How could the microplastics be collected ?
• How would the treatment work ?
• How can we assure biosafety ?

Which “receiving” bacteria could be used ?
The receiving bacteria or “the chassis” could be Escherichia Coli. In fact, E. coli is a rod-shaped (bacillus) Gram-negative bacterium that is frequently used as a model organism. Factors such as its ability to grow fast using cheap media and availability of molecular tools to perform genetic manipulations are favorable for using E. coli as a model organism in molecular genetics and synthetic biology.

How could the microplastics be collected ?
During the Delta event in which we participated we were able to meet and exchange with IADYS (https://www.iadys.com/en/). IADYS is a startup committed to preserving the marine ecosystem with their Jellyfish Bot presented in Figure 1. The Jellyfish Bot is a robot that is able to collect everyday waste on the surface of the Water. After exchanging with them we found out that their robot used a net capable of capturing microplastics which would be the perfect instrument to collect them from the ocean and treat them after that. They proposed to either lend us their robot so that we could collect microplastics in the mediterranean sea by ourselves or put us in touch with laboratories that they work with and send the microplastics they collect too.

How would the treatment work ?
Once the microplastics arrive at our plant using the jellyfish bot robot, we will feed our genetically modified E. coli with these microplastics. In fact the bacteria will be stored in a big biocontainer with all the nutrients necessary to their survival except for a carbon source, and will be able to survive by using microplastics as a carbon source. In fact, the modified bacteria will be able to attach to this microplastics thanks to their modified type IV pili, to secrete the plasticosome that will attach to the microplastics and then to degrade it thanks to the degrading enzymes. Because there will not be another carbon source for the bacteria to survive, it will be forced to degrade the microplastics to use them as carbon sources.

How can we assure biosafety ?
The biosafety of our project can be ensured mainly because the bacteria are not supposed to leave the biocontainer. But we also know that sometimes accidents haven, and the population is still very skeptical about the use of GMOs. We therefore will have to implement a biocontainment approach. We can opt for a system in which we can make the bacteria deficient of an essential gene for their metabolism, and without an external contribution the bacteria wouldn’t be able to survive. That way, even if the bacteria finds a way out of the biocontainer, it won’t survive because we will be giving to it a nutrient that she needs because she can’t synthyse it herself, and that it’s not found very easily in the environment. In addition, in order to face people's opinions on our solution, we will have to set up a project on scientific vulgarization to educate people on how GMOs can be used efficiently and safely.