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Etude des mécanismes physiologiques et moléculaires permettant la prise en charge des substrats hydrophobes par la levure Yarrowia lipolytica au niveau pariétal

Abstract : Yarrowia lipolytica can grow on many hydrophobic substrates and metabolize them via the β-oxidation pathway or store them into lipid bodies. The first contact between the cell and the hydrophobic substrates is by the cell wall. In this step, cell-wall proteins (CWP), β-glucane and chitin of the cell wall could play an important role for the adhesion and uptake of hydrophobic substrates. The aim of this work was to study the effect of a hydrophobic carbon source (compared with glucose) and the culture medium composition on the cell wall composition and the melanin production by Y. lipolytica. The results of our biochemical and molecular analysis showed that the presence of methyl oleate and the nutrients composition of the culture media have induced some modifications at the cell wall level. These modifications were linked with the adhesion or not of the lipid droplets to the cell surface; with a modified content of the cell wall components; with a resistance to compounds that are toxic for the cell wall, and with the modification of the expression patterns of 27 CWP genes analyzed in this work. The identity of the over-expressed CWP genes suggests the participation of their proteins in the cell wall integrity, in the adhesion of lipid droplets and in the stress response to methyl oleate and/or the nitrogen starvation. Our results have also shown that the presence of the lipids methyl oleate, castor oil and methyl ricinoleate induced the production of DHN-melanin by a mutant strain in which the β-oxidation is affected
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Cynthia Romero Guido. Etude des mécanismes physiologiques et moléculaires permettant la prise en charge des substrats hydrophobes par la levure Yarrowia lipolytica au niveau pariétal. Sciences agricoles. Université de Bourgogne, 2012. Français. ⟨NNT : 2012DIJOS022⟩. ⟨tel-00825481⟩

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