Présentation
Methanogenesis is an archaeal-specific metabolism that could have been active as early as 3.5 Gy ago with a direct impact on the evolution of the Earth’s climate system, as well as on current global changes. Methanogens are present in all types of anaerobic environments, from marine sediments to the human gastrointestinal tract, and are key players in the anaerobic degradation of organic matter. They are also essential for the valorisation of urban, industrial and agricultural waste into methane (used as a source of energy) and they are promising biotechnological tools for biosynthesis of molecules with high added value. Our knowledge of methanogenesis has been revolutionized over the past two years by the identification of a large number of novel uncultured lineages of methanogens only distantly related to previously known ones. This has led to the discovery of several novel metabolic pathways using the canonical MCR complex, involved in methane formation and depletion, or a divergent MCR complex (MCR-like complex), recently characterized and involved in short-chain-alkane oxidation. This important diversity of methane-related metabolisms and their wide phylogenetic distribution represent an ideal starting point to identify which one was the ancestral type of all, and to reconstruct the evolutionary and functional transitions that led to such diversity. The large number of these recent discoveries also suggests that other lineages of archaea with methane-related metabolism remain to be unveiled. Moreover, most of the recently described lineages are still poorly known as they were only studied through a small number of metagenome-assembled genomes (MAGs), having sometime a low completeness level. This could have led to incomplete or erroneous metabolic predictions and hampers large scale analysis of the evolution of these metabolisms. Moreover, it is now essential to culture representatives of these lineages in order to test the metabolic predictions derived from genomic analyses and to deepen our knowledge on the novel pathways and associated enzymes. METHEVOL is an interdisciplinary project coupling bioinformatic, molecular and cultural approaches. It has three main objectives: 1) Obtain high-quality MAGs corresponding to new and poorly known lineages of archaea with an MCR/MCR-like complex, to characterize them and gain insight into their energetic metabolism. 2) Use this newly generated data to reconstruct the origin of methane/short alkane metabolisms, and to study the evolutionary transitions that led to their diversity and their loss in some lineages. 3) Experimentally characterize the first member of a novel lineage of uncultured archaea, “Ca. Methanoliparia”, that we recently identified and for which we proposed a new type of metabolism coupling short-chain alkane oxidation and methanogenesis. This project will generate novel fundamental knowledge for the wide scientific community working on methanogens as key players of the biogeochemical cycles and climate regulation. Moreover, the genomic and experimental characterization of these new archaea can provide important information for the development of future biotechnological applications, in the production of biofuels, the degradation of organic matter in natural and anthropogenic environments or the biosynthesis of molecules with high added value.