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Apports des spectroscopies infrarouge et de fluorescence couplées à la chimiométrie pour la caractérisation de la structure de matrices fromagères et des relations structure-texture

Abstract : The intestinal microbiota constitutes a rich and varied enzymatic activities tank. Its expression is an integral part of the organism's physiology and has an influence on its health. The methanogenic Archaea, whose detection by classic cultural methods is difficult, are so far represented only by two hydrogenotrophic Methanobacteriales in this microbiota : Methanobrevibacter smithii and Methanosphaera stadtmanae. The purpose of this thesis was to bring a molecular vision of the diversity of the methanogenic Archaea of the microbiota and to look for the influence of age on this community. The research has been led by the analysis of the mcrA cistron, a specific molecular marker of methanogenesis, and of the 16S rRNA gene. It has revealed that the archaeal diversity colonizing this ecosystem is increased by new phylotypes which cannot be attached to any of the 5 previously described methanogenic orders, and may correspond to other methanogens affiliated to Thermoplasmatales or cohabiting with unknown Thermoplasmatales. Their frequency appears to be associated with their host's age, according to a study carried out on 63 individuals of different age-groups : 23 newborns (3 weeks to 10 months), 20 adults (from 25 to 45 years) and 20 elderly (from 70 to 90 years). A relation with the host's ageing is therefore possible. Finally, the potentiality of a 6th order of methanogenic Archaea distantly related to a group of Archaea which anaerobicaly oxidized methane, the ANME 1, and its surprising association recovered with unknown Archaea affiliated with Thermoplasmatales, raises the question on the phylogenetic origin of these various microorganisms and underlines our current relative ignorance of one ofthe three domain of life.
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Tahar Boubellouta. Apports des spectroscopies infrarouge et de fluorescence couplées à la chimiométrie pour la caractérisation de la structure de matrices fromagères et des relations structure-texture. Alimentation et Nutrition. Université Blaise Pascal - Clermont-Ferrand II, 2008. Français. ⟨NNT : 2008CLF21906⟩. ⟨tel-00726362⟩

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