Spatial and temporal variations of microbial communities in alpine tundra soils

• Main Author: Zinger, Lucie
• Other Authors: Laboratoire d'Ecologie Alpine (LECA), Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry ), Max Planck Institute for Marine Microbiology, Max-Planck-Gesellschaft, Université Joseph-Fourier - Grenoble I, Roberto Geremia([e-mail]), MicroAlp
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2009
• Subjects: microorganisms; community ecology; seasonal dynamics; snow cover regimes; biogeography; biogéographie; micro-organismes; CE-SSCP; écologie des communautés; dynamiques saisonnières; régimes d'enneigements; [SDV.EE]Life Sciences [q-bio]/Ecology; environment; Tundra
• Online Access: https://tel.archives-ouvertes.fr/tel-00421411; https://tel.archives-ouvertes.fr/tel-00421411/document; https://tel.archives-ouvertes.fr/tel-00421411/file/These_Lucie_Zinger.pdf

Microorganisms play a crucial role in ecosystem processes. Understanding the spatio-temporal distribution of microbial communities is thus a central issue, especially in a context of global changes. Microorganisms are largely diverse, but given that the great part of them is still uncultured, the use of suitable tools is required to evaluate their huge diversity and the factors responsible for the community assembly. Alpine ecosystems display strong mesotopographical and snow cover regime gradients. These environmental gradients create a strong spatial heterogeneity in plant cover and ecosystem processes at reduced scales. Alpine tundra are also submitted to strong temporal contrasts, due the very low temperatures occurring during winter. These ecosystems are thus well suited to study the dynamic and spatial patterns of soil microbial communities. This work first focused on the improvement of a molecular fingerprint technique, CE-SSCP, but also on the development of statistical tools for the analysis of DNA sequences. Soil bacterial, fungal and crenarchaeal communities were followed up over two years by using CESSCP and cloning/sequencing, in two habitats contrasted by their snow cover regimes. This study was then extended at the landscape scale, under different plant covers. This work shows that microbial communities' assembly in alpine soils varies throughout seasons and that winter conditions constitute a strong selective event. This study also shows that microbial communities are spatially distributed according to snow cover regimes and plant cover. The factors directly involved in such patterns are discussed. Les micro-organismes jouent un rôle crucial dans les processus écosystémiques. L'étude de la distribution spatio-temporelle des communautés microbiennes est donc nécessaire, particulièrement dans un contexte de changements globaux. Les micro-organismes étant très diversifiés et majoritairement non cultivables, l'étude de leur diversité et des facteurs responsables de l'assemblage des communautés ...