Micromagnétometrie à sonde Hall – DREP

Our conceptual perception of the functioning of aquatic pelagic ecosystems has significantly increased during the past decennia, with continuous technical and analytical advances. In particular, molecular approaches have allowed discovery of unknown biological entities or organisms in the three main Domains of the life (Archaea, Bacteria, and Eukarya) and in the proposed additional Domain of 'Akamara' that comprises infectious biological agents such as viruses. Using similar approaches, we have recently published a pioneer paper (Lefèvre et al. 2007) where fungi, belonging primarily to the endemic aquatic phylum of chytridiomycota, are unveiled as important members of the biological diversity in the plankton. We provide evidence that both vegetative (sporangia) and dispersal (flagellated zoospores) life stages of these organisms have been mis-identified as picoflagellated protists, i.e. the main bacterivores in the plankton, in previous studies. This raises an interesting new hypothesis in the context of carbon fluxes in pelagic systems and the related biogeochemical cycles: the carbon reservoir of heterotrophic protists and the related major pathway of carbon transfer via bacterivory are biased due the interference from fungi. The present project aims to explore the biodiversity, population dynamics and functional roles of fungi in pelagic systems, in order to propose improved mathematical models of carbon fluxes that include fungi as a new biological compartment. Further development of analytic (Fourier transformed infrared) and molecular techniques (probes, FISH, Clone-FISH, RT-PCR, DNA-SIP, functional genomic) is foreseen in the frame of DREP, to get inside of astonishing fungal pool in pelagic systems and to mine for novel knowledge of ecological importance. The application of analytical, biochemical, microbiological, molecular biological studies for detailed characterization of pelagic fungi and their potential roles in microbial trophic networks is foreseen in the frame of the DREP proposal. DREP is thus within the innovative and exploratory frame of the 'ANR Blanc' Program, and will allow consideration of a 'novel' compartment of eukaryotic microorganisms in the structure, dynamics and metabolism of pelagic ecosystems.