“The green yeast”

Chlamydomonas reinhardtii is in some way the “green” equivalent of yeast. Just like this fungus, it is unicellular, small and easy to cultivate in a laboratory. A simple Petri dish – a small plastic container with a gelled nutritional liquid in the bottom – is sufficient for it to multiply significantly. It is also possible to grow cultures in a liquid medium.

Furthermore, its genome is easy to manipulate. Researchers can easily produce mutants. Far from being monsters straight out of a horror film, these genetically modified organisms allow us to study the exact function of proteins. By eliminating or altering one of the genes, scientists can completely change the “translation” of these DNA fragments into effective proteins. Subsequently, these genes will no longer play their usual role. It is these changes of “behaviour” in these Chlamy mutants that allow researchers to find out which protein plays which role.

But what is the purpose of finding out such in-depth information on an organism which most people have not heard about? Besides satisfying the curiosity of scientists, the final goal, of course, is to make discoveries that could be used in order to more or less improve our living conditions.

Close-up on Chlamy’s breathing

In the Genetics of Microorganisms Laboratory, Pierre Cardol’s mission was to determine the componants of the protein complexes at the basis of Chlamy's breathing mechanisms. While everyone knows that plants are photosynthetic organisms, they are often unaware that they breathe! This breathing occurs in the mitochondria, intercellular organelles. In fact, this involves the transformation of nutriments obtained during photosynthesis: from this organic matter and in the presence of oxygen, the alga will produce carbon dioxide and water by releasing energy. This process requires the intervention of numerous protein complexes which are still relatively unknown. Pierre Cardol therefore attempted to find out more. He analysed a hundred genes linked to breathing. “We discovered that the first complex contains more than 40 proteins,” explains the researcher, “30 of which are present in all eukaryote organisms”. An observation that allows us to confirm that these proteins are important, and maybe even essential, for the correct functioning of the eukaryote cell. It is thanks to the use of mutants (see above) that the genetic of microorganism team managed to pinpoint certain interesting proteins. The use of systematic comparison computer program has then permitted to spot the presence of similar proteins in other organisms, including man.

“This research aims to bring therapeutic uses to the fore,” continues Pierre Cardol, “Chlamy also serves as a model to study the impact of mutations responsible for certain deficiencies in man. By revealing these mutations, we can advance in the elaboration of possible treatments”.