Characterization of prokaryotic microbial communities in Pyrenean peatlands : diversity, distribution and functional role

• Main Author: Richy, Étienne
• Other Authors: Institut des sciences analytiques et de physico-chimie pour l'environnement et les materiaux (IPREM), Université de Pau et des Pays de l'Adour (UPPA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Université de Pau et des Pays de l'Adour, Béatrice Lauga, François Rigal
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2021
• Subjects: Peatland; Microbial diversity; Ecology; Genomics; Carbon cycling; Physico-chemical parameters; Tourbière; Diversité microbienne; Écologie; Génomique; Cycle du carbone; Paramètre physico-chimique; [SDV.BC]Life Sciences [q-bio]/Cellular Biology; Austral; Subarctic
• Online Access: https://tel.archives-ouvertes.fr/tel-03685188; https://tel.archives-ouvertes.fr/tel-03685188/document; https://tel.archives-ouvertes.fr/tel-03685188/file/thesisrichy.pdf

Microorganisms are the key factors in plant litter decomposition, and directly influence the storage and release of carbon. In peatlands, microbial activity is inhibited by the concomitant anoxic, acidic, and poor nutrient conditions. As a result, peatlands store one-third of global soil carbon pool, while they occupy only 3% of the global land surface. Although smaller than boreal, austral, and subarctic peatlands, mountain peatlands located at lower latitudes are less studied but deserve also our full attention. Thus, to investigate the diversity and the role of the microorganisms in the functioning of these unique ecosystems, we collected samples from four peatlands located in the Pyrenees. In a first study, we observed similar patterns in the structure of microbial communities in three high-altitude peatlands (Andorra and Spain), with the microbial diversity being highly stratified over the depth gradient and related also to the carbon/nitrogen mass ratio, bulk density and water content. In a second study carried out at the Bernadouze peatland (Ariège, France), and thanks to an intensive sampling, we showed that the season and microhabitats (e.g. hummock, hollow) had little influence on the structure of the microbial communities. Conversely, pH, distance to the water table and, to a lesser extent, the carbon/nitrogen mass ratio were identified as the major determinants of the variations in microbial community diversity and composition, reflecting a non-random spatial distribution of bacteria and archaea throughout the landscape. These results were confirmed by a genome-centric approach developed in a third study. The assembly of 290 unique genomes distributed in 27 different lineages showed that Acidobacteria were key bacteria in the functioning of the Bernadouze peatland, with the metabolic potential to degrade complex organic matter. Finally, a new lineage of a very abundant methanogenic archaea was discovered, suggesting that methanogenesis could be an important process in the Bernadouze peatland. Les ...