Team:Sorbonne U Paris/Plant
Plant
Our environmental issue:
Human activities are responsible for significant deterioration in fluvial ecosystems. The Seine basin covers a total area of 78 000 km², while the Seine river and its affluents flow through agricultural, industrial and high population density areas. On one hand, runoff waters get contaminated by several pollutants before joining the fluvial circulation. On the other hand, sewage arising from running water is also highly polluted. Nowadays, sewage is not directly released into the river but goes into water treatment plants that ensure its depollution up to a certain level. However, wastewater treatment plants are not efficient enough to rid water from particular pollutants like pesticides, antibiotics and synthetic hormones.
Our photosynthetic chassis:
Chlamydomonas reinhardtii is a photosynthetic green microalgae that has been massively studied and used as a model organism in plant biology. Its physiology and metabolism are well known, and both its nuclear and chloroplast genomes have been sequenced in 2007. Since Chlamydomonas reinhardtii is very well known and rather easy to modify genetically, it is an ideal chassis for synthetic biology. In addition, because of its autotrophic metabolism, the system created can be autonomous. Thus, we could imagine a system of water biofiltration by microalgae grown in a bioreactor with the products of CO2 fixation by photosynthesis as the only source of carbon. The use of phototrophic organisms in water treatment applications thus brings both the advantage of creating a low energy cost system, but also promotes the fixation of atmospheric carbon.
Our project:
We have focused our efforts on the bioremediation of the pesticide atrazine which, despite being banned by the EU in 2003, remains very persistent in the environment due to its chemical stability. To do so, we created a genetically modified strain of
Chlamydomonas
capable of degrading atrazine into cyanuric acid by expressing three enzymes involved in the degradation pathway of atrazine found in the bacterium
Pseudomonas sp. ADP
strain.
To prevent any environmental pollution due to an accidental spread of our engineered CR strain, we also imagined a kill switch device, based on a UV light sensible programmed cell death. This safeguard relies on the release of a nuclease anchored on the plasma membrane induced by COP1 and URV8 dimerisation. It will allow the assembly of the N-ter and C-ter of the TEV protease, addressing the nuclease to the nucleus. Thus, a UV light highpass filter would have to be implemented in our bioremediation filter.
Conclusion
We built our iGEM project around a photosynthetic chassis,
Chlamydomonas reinhardtii, to solve a current environmental issue. During this project, we achieved the design and cloning of most of our biobricks. We led literature/bibliographic research and experimental tests to highlight the relevancy of using microalgae for the bioremediation of hazardous compounds. Unfortunately we were not able to test the functionality and efficiency of our composite parts.
We hope that future iGEM teams get inspired by our project and push further the development of
Chlamydomonas reinhardtii
as
a bioremediation tool.