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Theses

Caractérisation de l'holobionte des isopodes par des approches omiques : exemple du processus de dégradation de la lignocellulose

Abstract : Isopods are good models to study interactions within the holobiont because they host a rich and diversified microbiota, whose composition is highly variable, depending on the environment and the host's life history traits. Some of their endosymbionts such as the feminizing bacteria Wolbachia, and their consequences on the evolutionary trajectory of hosts have been well characterised. A more global perspective of interactions within the holobiont and their impacts on the host’s fitness has been little considered. In this context, we used a combination of metagenomics, transcriptomics and gene expression analysis approaches to better understand the mechanisms and consequences of these interactions on the host's fitness. First, this thesis explores host-microbial interactions through the lignocellulose degradation process, which is essential for isopods’ nutrition. The host and microbiota’s enzymatic repertoires related to the degradation of lignocellulose have been identified in the woodlouse Armadillidium vulgare. The comparison of these two enzyme repertoires revealed their complementarity, suggesting a close collaboration between the host and its microbiota for lignocellulose degradation. The contribution of the host and its microbiota to this process was then quantified according to several diets with gene expression of CAZymes (enzymes specialized in lignocellulose degradation) and metabarcoding approaches. Secondly, the identification of the CAZymes repertoire in 64 transcriptomes of aquatic and terrestrial isopods provided new information on the evolutionary processes that have favoured the conquest of lands by isopods. This work was further developed by obtaining metagenomes of five isopod species to characterise lignocellulose deconstruction strategies in the holobiont. The reconstruction of bacterial genomes from metagenomes enabled us to identify other symbionts in isopods. We also have characterised a first virome of isopods, which shows that phages constitute an important part of the microbiota. They could play a crucial role as regulators of bacterial communities within the holobiont. All these studies illustrate the richness of interactions between the microbiota and the host in isopods for lignocellulose degradation, and open the way to new implications of the microbiota within the isopods’ holobiont.
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https://tel.archives-ouvertes.fr/tel-03190840
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Submitted on : Tuesday, April 6, 2021 - 4:34:09 PM
Last modification on : Wednesday, November 3, 2021 - 5:55:10 AM
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Marius Bredon. Caractérisation de l'holobionte des isopodes par des approches omiques : exemple du processus de dégradation de la lignocellulose. Biologie végétale. Université de Poitiers, 2019. Français. ⟨NNT : 2019POIT2318⟩. ⟨tel-03190840⟩

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