Diversité écologique et fonctionnelle des champignons décomposeurs du bois : l'influence du substrat de la communauté à l'enzyme

Abstract : Saprophytic fungi are key players of dead organic matter recycling in forest ecosystems. These microorganisms possess the unique ability to degrade the integrality of wood constitutive polymers by secretion of complex oxydative and hydrolytic enzymatic systems. Communities structuration analysis during the initial stages of wood colonisation by high throughput sequencing revealed that the latter beyond being a source of nutrients, influences the distribution and dynamic of communities by its broad chemical variability. At the organism level, the different ecological groups of wood decomposing fungi possess extracellular degradation systems reflecting this chemical complexity. Genome sequencing of these organisms allowed the identification of enzymes superfamilies involved in resistance and detoxification mechanisms towards exogenous toxic compounds. Among them, the glutathione transferases superfamily exhibit extension of specific classes in wood decaying basidiomycetes. Biochemical and structural properties determination of one isoform belonging to one of these specific classes (the Etherase-like), found in Phanerochaete chrysosporium revealed unusual characteristics. This enzyme possesses an atypical dimerization mode as well as the ability to sequestrate toxic phenolic compounds resulting from wood degradation through a unique ligandin property. Properties comparison of several isoforms from this class belonging to C. cinereus and P.chrysosporium demonstrated a huge intra- and interspecific versatility of their enzymatics activities and ligandin property in response to environmental constraints arising from the great chemical heterogeneity of wood composition
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Yann Mathieu. Diversité écologique et fonctionnelle des champignons décomposeurs du bois : l'influence du substrat de la communauté à l'enzyme. Biologie végétale. Université de Lorraine, 2012. Français. ⟨NNT : 2012LORR0255⟩. ⟨tel-01749638⟩

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