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Mode de reconnaissance hôte symbionte en milieux extrêmes : cas du modèle symbiotique Rimicaris exoculata

Abstract : Deprived of light, the deep-sea hydrothermal vents are extremes ecosystems sustained by micobial chemosynthesis. These environments are colonized by animal species living in close relationships with these chemoautotrophic micro-organisms, eating them or establishing long term interactions with them, may they be trophic or not only. The shrimp Rimicaris exoculata is an endemic hydrothermal species of the Mid-Atlantic Ridge (MAR) sites. This crustacean represents the predominant macrofauna of some sites of the MAR. It lives in symbiotic association with two distinct microbial communities qualified as ectosymbiosis. One is located in its gill chamber and one in its gut. First, this work focused on the study of bacterial communication (Quorum Sensing or QS) within the ectosymbiontic communities during the molting and life cycles of R. exoculata. Then, we focused on an antimicrobial peptide (AMP) identification and search for its function in R. exoculata immunity and in controlling symbionts. Two QS genes (luxS and luxR) were identified in the R. exoculata ectosymbiontic community at different shrimp molt stages and life stages at the Rainbow, TAG, Snake Pit and Logatchev vent sites.As these genes are more divergent than that of 16S rRNA, they could be then used as biogeographical genetic markers tools to trace back the origin of individuals to a location or between locations along its life cycle. This work reports also the first description of an AMP in an extremophile arthropod (namely Recrustin). Data suggest a participation of this AMP in the control of the ectosymbiosis in Rimicarisexoculata. All this work provides new hypotheses wich are discussed in the manuscript, dealing with the interaction between symbionts and Rimicaris exoculata.
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Simon Le Bloa. Mode de reconnaissance hôte symbionte en milieux extrêmes : cas du modèle symbiotique Rimicaris exoculata. Microbiologie et Parasitologie. Université de Bretagne occidentale - Brest, 2016. Français. ⟨NNT : 2016BRES0119⟩. ⟨tel-02003354⟩

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