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Etude in vitro des propriétés probiotiques de bactéries du genre Bacillus : Interaction avec l’hôte et effets de l’association avec un prébiotique

Abstract : Probiotics are live microorganisms, which when administered in adequate amounts confer a health benefit on the host. Bacillus probiotic strains are not able to colonize the gut, and are considered as transient residents of the microbiota. Prebiotic are non-digestible food ingredients that could stimulate growth of bacteria in the gut. This work investigates the in vitro effect of a prebiotic isomaltooligosaccharide (IMOS) on the growth of a probiotic strain Bacillus subtilis. This study highlights the ability of the strain to use IMOS as unique carbon source. A comparative proteomic analysis investigates the main enzymes implicated in the prebiotic metabolism, and biomarkers possibly involved in probiotic effects. This preliminary work, which studies the synbiotic association between a probiotic and a prebiotic, will lead to in vivo assays. Beneficial effects of probiotic Bacilli, mainly modulation of intestinal immune system, result from interaction between bacterial cell-wall molecules and intestinal cells. The molecular origin of immunomodulatory mechanisms are poorly understood, while understanding is needed to optimize the use of probiotics. A second part of this work consists in comparing the structure of a molecular cell-wall component named lipoteichoic acids (LTA) from three Bacillus probiotic, a molecular cell-wall component of Gram positive bacteria, and their immunological activity. A structural study, using biochemical determinations and NMR spectroscopic analysis, highlights the structural diversity between LTAs from different Bacillus species. The key role of D-alanine substituents in the biological activity of these bacterial antigens has been demonstrated.
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Submitted on : Monday, September 18, 2017 - 11:36:26 AM
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Romain Villeger. Etude in vitro des propriétés probiotiques de bactéries du genre Bacillus : Interaction avec l’hôte et effets de l’association avec un prébiotique. Autre. Université de Limoges, 2014. Français. ⟨NNT : 2014LIMO0066⟩. ⟨tel-01589104⟩

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