Recherche avancée
Affichage des résultats 701 à 720 sur 1453 au total
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Sensibilisation à l'identification des violences sexistes et sexuelles au travail
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Soutenance d'HDR Etienne Rajon
Emergence et évolution du métabolisme
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Modelling microbial evolution: from ecological interactions to developmental programs
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Rapid evolution of robustness following colonization of a new environment
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Soutenance de thèse de Jessica Cachelou
Vers une meilleure compréhension de la démographie des populations naturelles : le sanglier comme cas d’étude
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Soutenance d'HDR Damien de Vienne
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Decoding the Secrets of Asexual Evolution and Extreme Survival in bdelloid rotifer Adineta vaga
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Soutenance d'HDR Matthieu Boulesteix
Les éléments transposables dans les populations en expansion : dynamique et contribution à l’adaptation
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The identity of ecosystems: an evolutionary approach
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Can we do more with less ? Qualitative discrete-event models of ecological systems and their formal analysis
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Soutenance HDR Laure Ségurel
How are species adapting to their environment: Positive selection, balancing selection, and gut microbiota
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Retraite du laboratoire / Lab retreat
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Host phylogeny and diet drive the structure of mammalian microbial communities at different phylogenetic scales
Bacterial communities (microbiota) living in Mammal guts are composed of thousands of bacterial species that are essential for host physiology, immunity and diet. It has been shown that host phylogeny (genetics and immune system of the host) and diet are the two major factors driving the composition of gut microbiota. However, major questions remain: (i) the relative contribution of host phylogeny and diet at short and long time scales is highly debated and the two processes are not well characterized, (ii) host phylogeny may drive the composition through co-evolution with bacterial lineages or through niche selection, with closely-related hosts retaining similar bacteria from the environment. Here, we show that host phylogeny and diet are for the most part independent processes and do not drive the bacterial composition at the same taxonomic scale. Diet determines what lineage is present or not at deep bacterial phylogenetic levels through gain or loss of lineages creating nested communities. Host phylogeny, however, selects the lineages at finer scales through true turnover of lineages, consistent with a more stringent selection of tolerated antigens. Finally, it appears that co-speciation between hosts and bacterial lineages plays a minor role in driving the correlation between community composition and host phylogeny, suggesting that environmental filtering by host genetics is the dominant process at selecting bacterial lineages. Our results shed light on the long-timescale evolutionary dynamic of gut bacterial communities, which are multi-layered phylogenetic structures shaped very differently by host phylogeny and diet.
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Gathering, updating, and calibrating phylogenies for The Open Tree of Life
The Open Tree of Life project is a collaborative effort to synthesize, share, and update a comprehensive phylogeny of all 2.3 million named species. We have completed a draft synthesis of a single tree from hundreds of phylogenetic estimates using taxonomy as a scaffold. This synthesis is not static but rather will be continually revised as new data become available. This undertaking requires development of both novel infrastructure and analysis tools. I will discuss three components of this project: Phylesystem, an open database and web application for community curation of phylogenies using a git-based datastore, PhyScraper, a pipeline to continually update phylogenetic estimates as new data is generated, and FastDate, an algorithm to rapidly generate maximum a posteriori estimates of time-calibrated trees, even for phylogenies with hundreds or thousands of tips. Together, these developments reduce impediments to accessing, analyzing and reusing the phylogenetic information which is essential to biological research today.
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Transitions between combined and separate sexes in plants
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Characterisation of the bacterial replicons
The genome of bacteria is classically separated into essential, stable and slow evolving replicons (chromosomes) and accessory, mobile and rapidly evolving replicons (plasmids). This paradigm is being questioned since the discovery of genomic elements that possess both chromosomal and plasmidic features. These Extra-Chromosomal Essential Replicons (ECERs), be they called "megaplasmids", "secondary chromosomes" or "chromids", are found in diverse lineages across the bacterial phylogeny and are generally believed to be modified plasmids. However, their true nature and the mechanisms permitting their integration within the sable genome are yet to be formally determined. The relationships between replicons, with reference to their Genetic Information Inheritance Systems (GIIS), were explored under the assumption that the inheritance of ECERs is integrated to the cell cycle and highly constrained in contrast to that of standard plasmids. A global comparative genomics analysis including all available complete bacterial genome sequences, was performed using GIIS functional homologues as parameters and applying several analytical procedures. GIIS proved appropriate in characterizing the level of integration within the stable genome, as well as the origins, of the replicons. The study of ECERs thus provides clues to the genetic mechanisms and evolutionary processes involved in the replicon stabilization into the essential genome and to the continuity of the genomic material.
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A turtle view of the evolution of genomes and sex determination
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