18 research outputs found
Ătude du pangĂ©nome dâune population bactĂ©rienne structurĂ©e : vers une nouvelle comprĂ©hension de lâorigine des variations intra-gĂ©nomiques
Evolutionary models associated with species concepts underlie selective sweep processes at the gene or genome scale. In this thesis, a reconsideration of the processes underlying the differentiation of free-living bacterial populations from the environment was carried out using co-occurring subpopulations of the Prochlorococcus HLII ecotype as models. The objective was to understand the evolutionary forces driving the formation and maintenance of the pangenome for environmental free-living bacterial populations.The Prochlorococcus pangenome appears to be open at the population level. The core and flexible genes that make up the pangenome form a genomic landscape characterised by conserved and variable regions. This genomic organisation is accompanied by a non-random distribution of the functions carried by the flexible genes and by differential evolutionary dynamics, illustrated by a variation in selective constraints and the identification of recombination hotspots along the genome.The results obtained in this work reveal distinct evolutionary trajectories of sets of genes, specific to particular genomic compartments, in a structured population. This is consistent with a drift-barrier model of evolution. Furthermore, the structuring of genetic information along the genome may depend on the dynamics of gene flow between subpopulations, especially for flexible genes. Rather than non-random acquisition of genes according to their genomic location, a differential probability of retention of transferred genes as a consequence of fluctuating effective population size along the genome might be considered.Les modĂšles dâĂ©volution associĂ©s aux concepts de lâespĂšce mettent en avant des processus de balayage sĂ©lectif Ă lâĂ©chelle des gĂšnes ou Ă lâĂ©chelle des gĂ©nomes. Au cours de cette thĂšse, une reconsidĂ©ration des processus Ă lâorigine de la diffĂ©renciation de populations bactĂ©riennes libres environnementales a Ă©tĂ© rĂ©alisĂ©e en prenant comme modĂšle des sous-populations cooccurrentes de lâĂ©cotype HLII de Prochlorococcus. Lâobjectif Ă©tait dâapprĂ©hender les forces Ă©volutives Ă lâorigine de la formation et du maintien du pangĂ©nome pour des populations bactĂ©riennes libres de lâenvironnement.Le pangĂ©nome de Prochlorococcus apparaĂźt ouvert Ă lâĂ©chelle populationnelle. Les gĂšnes core et flexibles qui le composent dessinent un paysage gĂ©nomique caractĂ©risĂ© par des rĂ©gions conservĂ©es et variables. Cette organisation gĂ©nomique sâaccompagne dâune rĂ©partition non alĂ©atoire des fonctions portĂ©es par les gĂšnes flexibles et dâune dynamique Ă©volutive diffĂ©rentielle, illustrĂ©e par une variation des contraintes sĂ©lectives et lâidentification de points chaud de recombinaison, le long du gĂ©nome.Les rĂ©sultats obtenus au cours de ces travaux mettent en Ă©vidence une distinction des trajectoires Ă©volutives dâensembles de gĂšnes, spĂ©cifiques de compartiments gĂ©nomiques particuliers, dans une population structurĂ©e. Ceci est conforme Ă une Ă©volution de type barriĂšre Ă la dĂ©rive. En outre, la structuration de lâinformation gĂ©nĂ©tique le long du gĂ©nome pourrait dĂ©pendre de la dynamique des flux de gĂšnes entre les sous-populations, en particulier pour les gĂšnes flexibles. PlutĂŽt quâune acquisition non alĂ©atoire des gĂšnes en fonction de leur localisation gĂ©nomique, une probabilitĂ© diffĂ©rentielle de rĂ©tention des gĂšnes transfĂ©rĂ©s comme consĂ©quence de la fluctuation de la taille efficace de la population le long du gĂ©nome peut ĂȘtre envisagĂ©e
Ătude du pangĂ©nome dâune population bactĂ©rienne structurĂ©e : vers une nouvelle comprĂ©hension de lâorigine des variations intra-gĂ©nomiques
Evolutionary models associated with species concepts underlie selective sweep processes at the gene or genome scale. In this thesis, a reconsideration of the processes underlying the differentiation of free-living bacterial populations from the environment was carried out using co-occurring subpopulations of the Prochlorococcus HLII ecotype as models. The objective was to understand the evolutionary forces driving the formation and maintenance of the pangenome for environmental free-living bacterial populations.The Prochlorococcus pangenome appears to be open at the population level. The core and flexible genes that make up the pangenome form a genomic landscape characterised by conserved and variable regions. This genomic organisation is accompanied by a non-random distribution of the functions carried by the flexible genes and by differential evolutionary dynamics, illustrated by a variation in selective constraints and the identification of recombination hotspots along the genome.The results obtained in this work reveal distinct evolutionary trajectories of sets of genes, specific to particular genomic compartments, in a structured population. This is consistent with a drift-barrier model of evolution. Furthermore, the structuring of genetic information along the genome may depend on the dynamics of gene flow between subpopulations, especially for flexible genes. Rather than non-random acquisition of genes according to their genomic location, a differential probability of retention of transferred genes as a consequence of fluctuating effective population size along the genome might be considered.Les modĂšles dâĂ©volution associĂ©s aux concepts de lâespĂšce mettent en avant des processus de balayage sĂ©lectif Ă lâĂ©chelle des gĂšnes ou Ă lâĂ©chelle des gĂ©nomes. Au cours de cette thĂšse, une reconsidĂ©ration des processus Ă lâorigine de la diffĂ©renciation de populations bactĂ©riennes libres environnementales a Ă©tĂ© rĂ©alisĂ©e en prenant comme modĂšle des sous-populations cooccurrentes de lâĂ©cotype HLII de Prochlorococcus. Lâobjectif Ă©tait dâapprĂ©hender les forces Ă©volutives Ă lâorigine de la formation et du maintien du pangĂ©nome pour des populations bactĂ©riennes libres de lâenvironnement.Le pangĂ©nome de Prochlorococcus apparaĂźt ouvert Ă lâĂ©chelle populationnelle. Les gĂšnes core et flexibles qui le composent dessinent un paysage gĂ©nomique caractĂ©risĂ© par des rĂ©gions conservĂ©es et variables. Cette organisation gĂ©nomique sâaccompagne dâune rĂ©partition non alĂ©atoire des fonctions portĂ©es par les gĂšnes flexibles et dâune dynamique Ă©volutive diffĂ©rentielle, illustrĂ©e par une variation des contraintes sĂ©lectives et lâidentification de points chaud de recombinaison, le long du gĂ©nome.Les rĂ©sultats obtenus au cours de ces travaux mettent en Ă©vidence une distinction des trajectoires Ă©volutives dâensembles de gĂšnes, spĂ©cifiques de compartiments gĂ©nomiques particuliers, dans une population structurĂ©e. Ceci est conforme Ă une Ă©volution de type barriĂšre Ă la dĂ©rive. En outre, la structuration de lâinformation gĂ©nĂ©tique le long du gĂ©nome pourrait dĂ©pendre de la dynamique des flux de gĂšnes entre les sous-populations, en particulier pour les gĂšnes flexibles. PlutĂŽt quâune acquisition non alĂ©atoire des gĂšnes en fonction de leur localisation gĂ©nomique, une probabilitĂ© diffĂ©rentielle de rĂ©tention des gĂšnes transfĂ©rĂ©s comme consĂ©quence de la fluctuation de la taille efficace de la population le long du gĂ©nome peut ĂȘtre envisagĂ©e
Ătude du pangĂ©nome dâune population bactĂ©rienne structurĂ©e : vers une nouvelle comprĂ©hension de lâorigine des variations intra-gĂ©nomiques
Evolutionary models associated with species concepts underlie selective sweep processes at the gene or genome scale. In this thesis, a reconsideration of the processes underlying the differentiation of free-living bacterial populations from the environment was carried out using co-occurring subpopulations of the Prochlorococcus HLII ecotype as models. The objective was to understand the evolutionary forces driving the formation and maintenance of the pangenome for environmental free-living bacterial populations.The Prochlorococcus pangenome appears to be open at the population level. The core and flexible genes that make up the pangenome form a genomic landscape characterised by conserved and variable regions. This genomic organisation is accompanied by a non-random distribution of the functions carried by the flexible genes and by differential evolutionary dynamics, illustrated by a variation in selective constraints and the identification of recombination hotspots along the genome.The results obtained in this work reveal distinct evolutionary trajectories of sets of genes, specific to particular genomic compartments, in a structured population. This is consistent with a drift-barrier model of evolution. Furthermore, the structuring of genetic information along the genome may depend on the dynamics of gene flow between subpopulations, especially for flexible genes. Rather than non-random acquisition of genes according to their genomic location, a differential probability of retention of transferred genes as a consequence of fluctuating effective population size along the genome might be considered.Les modĂšles dâĂ©volution associĂ©s aux concepts de lâespĂšce mettent en avant des processus de balayage sĂ©lectif Ă lâĂ©chelle des gĂšnes ou Ă lâĂ©chelle des gĂ©nomes. Au cours de cette thĂšse, une reconsidĂ©ration des processus Ă lâorigine de la diffĂ©renciation de populations bactĂ©riennes libres environnementales a Ă©tĂ© rĂ©alisĂ©e en prenant comme modĂšle des sous-populations cooccurrentes de lâĂ©cotype HLII de Prochlorococcus. Lâobjectif Ă©tait dâapprĂ©hender les forces Ă©volutives Ă lâorigine de la formation et du maintien du pangĂ©nome pour des populations bactĂ©riennes libres de lâenvironnement.Le pangĂ©nome de Prochlorococcus apparaĂźt ouvert Ă lâĂ©chelle populationnelle. Les gĂšnes core et flexibles qui le composent dessinent un paysage gĂ©nomique caractĂ©risĂ© par des rĂ©gions conservĂ©es et variables. Cette organisation gĂ©nomique sâaccompagne dâune rĂ©partition non alĂ©atoire des fonctions portĂ©es par les gĂšnes flexibles et dâune dynamique Ă©volutive diffĂ©rentielle, illustrĂ©e par une variation des contraintes sĂ©lectives et lâidentification de points chaud de recombinaison, le long du gĂ©nome.Les rĂ©sultats obtenus au cours de ces travaux mettent en Ă©vidence une distinction des trajectoires Ă©volutives dâensembles de gĂšnes, spĂ©cifiques de compartiments gĂ©nomiques particuliers, dans une population structurĂ©e. Ceci est conforme Ă une Ă©volution de type barriĂšre Ă la dĂ©rive. En outre, la structuration de lâinformation gĂ©nĂ©tique le long du gĂ©nome pourrait dĂ©pendre de la dynamique des flux de gĂšnes entre les sous-populations, en particulier pour les gĂšnes flexibles. PlutĂŽt quâune acquisition non alĂ©atoire des gĂšnes en fonction de leur localisation gĂ©nomique, une probabilitĂ© diffĂ©rentielle de rĂ©tention des gĂšnes transfĂ©rĂ©s comme consĂ©quence de la fluctuation de la taille efficace de la population le long du gĂ©nome peut ĂȘtre envisagĂ©e
L'Ătat contre ou avec le territoire ? La formation professionnelle et universitaire en tension entre logiques centrales et volontĂ© d'action des rĂ©gions. ST 12 : L'Ătat et ses territoires : nouvelles logiques, nouvelles relations ?
En ligne sur http://www.congres-afsp.fr/Le vaste domaine de l'Ă©ducation et de la formation se prĂȘte particuliĂšrement bien Ă l'examen des recompositions de l'action de l'Ătat, du dĂ©ploiement de diffĂ©rentes Ă©chelles de gouvernement et des conditions de fabrique de l'action publique territoriale (voir Faure, Muiller, 2007). En premier lieu, il reprĂ©sente la premiĂšre composante des budgets rĂ©gionaux Ă travers l'exercice de compĂ©tences lĂ©gales (lycĂ©es, apprentissage, formations professionnelles) et d'interventions volontaires - en particulier en matiĂšre d'enseignement supĂ©rieur et recherche (Aust et Crespy, 2009) - ; en outre il mobilise une configuration d'acteurs particuliĂšrement foisonnante par l'entremise de diffĂ©rents processus de coordination : dĂ©volutions et dĂ©lĂ©gations de compĂ©tences, contractualisations, dĂ©centralisation et dĂ©concentration ... au point que l'enchevĂȘtrement des responsabilitĂ©s Ă©voque plus la figure du " crumble " que celle, dĂ©sormais classique, du " mille-feuilles " institutionnel. Cette construction, hĂ©ritĂ©e de multiples rĂ©formes et nĂ©gociations, serait-elle aujourd'hui marquĂ©e par un " retour " de " l'Ătat surplombant " (Salais, 1998) compte tenu d'initiatives gouvernementales peu concertĂ©es et souvent mĂȘme imposĂ©es par une technique qui s'apparenterait plus au " coup d'Ătat " (Padioleau, 1993) qu'Ă la patiente discussion entre des parties prenantes soucieuses d'Ă©laborer des rĂšgles lĂ©gitimes et durables (Reynaud, 2003) ? S'affirmerait ainsi une configuration sociĂ©tale assez paradoxale..
A driftâbarrier model drives the genomic landscape of a structured bacterial population
International audienc
New insights into the pelagic microorganisms involved in the methane cycle in the meromictic Lake Pavin through metagenomics
International audienceAdvances in metagenomics have given rise to the possibility of obtaining genome sequences from uncultured microorganisms, even for those poorly represented in the microbial community, thereby providing an important means to study their ecology and evolution. In this study, metagenomic sequencing was carried out at four sampling depths having different oxygen concentrations or environmental conditions in the water column of Lake Pavin. By analyzing the sequenced reads and matching the contigs to the proxy genomes of the closest cultivated relatives, we evaluated the metabolic potential of the dominant planktonic species involved in the methane cycle. We demonstrated that methane-producing communities were dominated by the genus Methanoregula while methane-consuming communities were dominated by the genus Methylobacter, thus confirming prior observations. Our work allowed the reconstruction of a draft of their core metabolic pathways. Hydrogenotrophs, the genes required for acetate activation in the methanogen genome, were also detected. Regarding methanotrophy, Methylobacter was present in the same areas as the non-methanotrophic, methylotrophic Methylotenera, which could suggest a relationship between these two groups. Furthermore, the presence of a large gene inventory for nitrogen metabolism (nitrate transport, denitrification, nitrite assimilation and nitrogen fixation, for instance) was detected in the Methylobacter genome
Meta-analysis of glyphosate contamination in surface waters and dissipation by biofilms
International audienc
Analysis of bacterial and archaeal communities associated with Fogo volcanic soils of different ages
International audienc
Interdisciplinary Participative Platforms to Ensure the Wellbeing of African City Dwellers
International audienc
Interdisciplinary Participative Platforms to Ensure the Wellbeing of African City Dwellers
International audienc