Affichage des résultats 1441 à 1460 sur 1465 au total
Thèse de Marion Roussel le vendredi 27 novembre 2015 à 9 h - amphithéâtre CNRS (Villeurbanne)
Vibrios have been associated with successive mortality outbreaks ofCrassostrea gigas) in France that have resulted in losses up to 100% of production. Given the near monoculture of C. gigas in Europe, there is an urgent need to understand the epidemiology of these outbreaks, particularly the role of Vibrio in the diseases.The study of the Vibrios distribution on fine phylogenetic and spatial scales has demonstrated that vibrios coexisting in the water column can be divided into closely related populations, which pursue different lifestyles i.e. ecological population (Hunt et al., 2008). However, a link between ecological populations and pathogenicity has not been demonstrated, and it is unclear whether pathogenicity is a trait primarily linked to clones or to populations comprising a large number of distinct genotypes.In the presentVibrio populations in an intensive oyster cultivation area. We demonstrate that Vibrio populations do not assemble neutrally in oysters from water column populations i.e. specific genotypes colonize the oysters. Combining experimental ecology, high throughput infection assay and genome sequencing, we showed that the onset of disease in oysters is associated with progressive replacement of diverse, benign colonizers by members of a phylogenetically coherent virulent population together with quorum sensing pheromone producers. Analyses of oyster mortality following experimental infection suggest that disease onset can be facilitated by the presence of non-virulent strains. Oyster disease may thus represent a new form of polymicrobial disease, in which non-pathogenic strains contribute to increased mortality.Hunt DE, et al. (2008) Resource partitioning and sympatric differentiation among closely related bacterioplankton. Science 320(5879):1081-1085.Lemire A, Goudenège D, Versigny T, Petton B, Calteau A, Labreuche Y, Le Roux F. (2014) Populations, not clones, are the unit of vibrio pathogenesis in naturally infected oysters. ISME J. Dec 9. doi: 10.1038/ismej.2014.233
Thèse de Sabine Patot - vendredi 10 juillet - 14h00 - Amphi du CNRS
HDR de Julien VARALDI le jeudi 13 décembre 2018 à 14 h, amphithéâtre Déambuatoire 1 (La Doua)
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UMR 5600 - Laboratoire Environnement Ville Société (EVS)
abstract: This talk introduces some of the ideas behind cophylogenetic analysis, which aims to recover ancient coevolutionary events between ecologically linked taxonomic units such as hosts and parasites, hosts & symbionts, species and genes. It describes some of the current challenges in this area, in terms of theoretical results, implementation, and some real examples.bio: M Charleston is an Associate Professor at the University of Sydney in Australia. He did his PhD at Massey University, and has worked at U.T. Austin, University of Glasgow, and University of Oxford. His research is mainly in evolutionary biology and bioinformatics.
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Conflicts between wolves and livestock have continued to escalate since wolf re-introduction in the Northern Rockies, USA. We will provide an overview wolf re-introduction, including trends in populations and predation rates. We will also review how wolves have (or have not) affected livestock management practices and ranch profitability. We will then review the legal framework for wolf control in Wyoming, including predation compensation policies. Compensation policies have attempted to reduce the impact of wolf-livestock conflicts by compensating producers for lost livestock. Compensation schemes, however, focus only on direct predation (i.e., confirmed losses) despite a growing body of evidence that predation pressure also have indirect effects on prey, particularly domesticated livestock (e.g., slower weight gain, higher disease rates, or lower reproduction rates). We will then discuss our research, which uses an economic model of livestock production to estimate the economic impact of both direct and indirect effects of wolf predation. Our results suggest that short-run (i.e., year-to-year) financial impacts of wolf indirect effects may be as large as or larger than the direct effects. Including indirect effects implies that the compensation ratio (i.e., number of calves compensated per confirmed depredation) necessary to fully offset the financial impacts of wolves would need to be two to three times larger than current 7:1 compensation ratio used in Wyoming.