Auswahl der wissenschaftlichen Literatur zum Thema „Adaptation des pathogènes“
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Zeitschriftenartikel zum Thema "Adaptation des pathogènes"
FLEITER, Bernard. „Les interférences occlusales sont-elles pathogènes ?“ Actualités Odonto-Stomatologiques, Nr. 290 (Juni 2018): 5. http://dx.doi.org/10.1051/aos/2018045.
Der volle Inhalt der QuelleMÉRAT, P., und A. BORDAS. „Les objectifs et les critères de sélection : Interactions génotype × environnement et adaptation au milieu chez les volailles“. INRAE Productions Animales 5, HS (02.12.1992): 175–78. http://dx.doi.org/10.20870/productions-animales.1992.5.hs.4282.
Der volle Inhalt der QuelleKornreich, C. „Utilité de la dépression : une approche évolutionniste“. European Psychiatry 28, S2 (November 2013): 13–14. http://dx.doi.org/10.1016/j.eurpsy.2013.09.032.
Der volle Inhalt der QuelleBreton-Torres, Isabelle, Manon Serre, Patrick Jammet und Jacques Yachouh. „Dysfonction de l’appareil manducateur : apport de la prise en charge rééducative“. L'Orthodontie Française 87, Nr. 3 (September 2016): 329–39. http://dx.doi.org/10.1051/orthodfr/2016030.
Der volle Inhalt der QuelleBernier, Louis. „Génomique des champignons ophiostomatoïdes : un gène, c’est bien; deux, c’est mieux; deux mille, c’est encore mieux!“ Phytoprotection 85, Nr. 1 (27.08.2004): 39–43. http://dx.doi.org/10.7202/008905ar.
Der volle Inhalt der QuelleIbraheem, R. M., und A. Issa. „Prematurity as a secondary immunodeficiency disorder with increased risk of infections: A mini-review“. African Journal of Clinical and Experimental Microbiology 25, Nr. 2 (03.04.2024). http://dx.doi.org/10.4314/ajcem.v25i2.2.
Der volle Inhalt der QuelleDissertationen zum Thema "Adaptation des pathogènes"
Guillemet, Martin. „The dynamics of viral adaptation : theoretical and experimental approaches“. Electronic Thesis or Diss., Université de Montpellier (2022-....), 2023. http://www.theses.fr/2023UMONG020.
Der volle Inhalt der QuelleMost living organisms on the tree of life can be infected by viruses. The ubiquity of viruses is driven by different factors including high mutation rates, high population sizes and low generation times, which allow for quick adaptation to very different host species. The dynamics of adaptation - the rate of change of the mean fitness of the viral population - results from the interplay between multiple evolutionary forces that may promote or hamper viral adaptation. But the interactions between these different factors may often be difficult to understand. During this PhD we developed a combination of theoretical and experimental approaches to disentangle the influence of some of these factors on viral adaptation.First, we explored the dynamics of viral adaptation to a homogeneous host population. We used Fisher’s Geometric Model of adaptation and studied the joint evolutionary and epidemiological dynamics of a viral population spreading in a host population. This modeled allowed us to explore the lethal mutagenesis hypothesis: is it possible to treat viral infections with mutagenic drugs to increase the mutation load of the viral population beyond a threshold that may result in the extinction of the within-host population? We show which parameters affect the critical mutation rate leading to viral extinction and we show how epidemiology and evolution can affect the transient within-host dynamics of the viral population when a single virus life-history trait (transmission rate) is under selection. We extend this modeling framework to study the joint evolution of transmission and virulence during the adaptation of an emerging pathogen. At the beginning of an epidemic, these two traits are expected to evolve independently but a trade-off may build up with viral adaptation.Second, we studied viral adaptation in heterogeneous host populations when the virus spreads among a diversified population of resistance host. We studied the evolutionary emergence of viruses: can viruses avoid extinction by the acquisition of escape mutations allowing them to infect some of the resistant hosts in the population? We developed a simple birth-death process to predict the probability of evolutionary emergence as a function of the composition of the host population. In particular, we show how the proportion of multiple resistant hosts can reduce the risk of pathogen evolutionary emergence. We put some of these predictions to the test using bacteriophages spreading in bacterial populations. We manipulate the diversity of CRISPR immunity in Streptococcus thermophilus bacteria and we confirm the key influence of multiple resistance on the risk of viral adaptation.Third, we also studied viral adaptation in time-varying environments where the host population is allowed to coevolve with the virus. In this experimental project we monitored the adaptation of bacteriophages as they coevolved with the CRISPR immunity of S. thermophilus bacteria. We track reciprocal adaptive changes in which bacteria acquire new layers of resistance (new spacers in the CRISPR array) and phages acquire new escape mutations in the corresponding protospacers. This experiment allows us to monitor the dynamics of viral adaptation across time and space. Interestingly, we find a significant asymmetries in competitive abilities among different bacterial strain in the absence of phage predation. This asymmetric competition has dramatic consequences on the maintenance of diversity of host resistance and on the coevolutionary dynamics with the virus. This thesis demonstrates the possibility to use experimental evolution with microbial microcosms to explore the validity of some theoretical predictions on the dynamics of viral adaptation. This experimental validation is particularly important if one wants to use evolutionary models to make public-health recommendations
Michon, Anne-Laure. „Les témoins de l'adaptation des bactéries pathogènes opportunistes associées à la mucoviscidose : des opérons ribosomiques aux implications thérapeutiques“. Thesis, Montpellier 1, 2013. http://www.theses.fr/2013MON13501/document.
Der volle Inhalt der QuelleBacterial microbiotae and human beings developed mutualist interactions. All disrupting factors impacting this equilibrium can modify relationships among microbiota members with diverse consequences. In such an unstable context, opportunistic bacterial pathogens (OBPs) of endogenous or environmental origin showing great adaptability may find favorable conditions leading to ecological niche extension or to new niche colonization. This is illustrated by the diversity of atypical bacteria as well as by genetic and genomic evolution of members of the cystic fibrosis (CF) respiratory tract (CFRT) microbiota. The deficit in local innate immunity allowed colonization by endogenous and exogenous bacteria that will further develop adaptation processes to this particular ecological niche. The aim of this study was to evaluate phenotypic, genetic and genomic potential adaptation markers in different models of OBPs, particularly in CF. For this purpose, we described the variability in the multiple rrs gene copies using PCR and temperature-based denaturing electrophoresis (PCR-TTGE) on large collections of Veillonella (n=149) and Achromobacter xylosoxidans (n=164), as well as on isolates of six other species involved in the CFRT colonization (Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Staphylococcus aureus, Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae). Genome dynamics of 90 isolates from 12 patients chronically colonized by A. xylosoxidans was studied by PCR-TTGE, restriction fragment length polymorphism analysis after pulsed-field gel electrophoresis and PCR on repetitive sequences. Finally, the effect of environmental stress was evaluated on part of the growing CF microbiota and a thorough study of NaCl effect on 85 CF P. aeruginosa isolates was performed.These different approaches highlight: i) the intragenomic heterogeneity of the rrs gene copies in Veillonella (74% of isolates), H. influenzae (61%), S. maltophilia (38%), A. xylosoxidans (28%), and S. aureus (17%), ii) a clonal chronic colonization with A. xylosoxidans in 12 CF patients associated with rrs genetic and/or genomic intra-clonal evolution, iii) the effect of environmental stress such as salinity, pH and temperature on the CFRT microbiota, iv) the antimicrobial effect of NaCl on CF P. aeruginosa isolates, a 6% NaCl concentration inhibiting the growth of all the isolates and a bactericidal action being observed for 90% of the isolates with 10% NaCl, v) multiple effects of NaCl on growth, biofilm and mobility of P. aeruginosa. This study shows that rrs genes and genome dynamics witness for bacterial adaptability within microbiota according to environmental constraints and underlines the diversity and importance of adaptation processes in the long-term pathological adapted microbial communities of the CFRT. Modification of environmental factors such as salinity or pH of the CFRT niche may impact the microbiota and should be considered as targets for CF therapeutics
Talagrand, Emilie. „Diversité, complexité et adaptation au comportement pathogène au sein du genre Aeromonas“. Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT123/document.
Der volle Inhalt der QuelleAeromonas groups ubiquitous bacteria mainly living in aquatic environments. These opportunistic pathogens for human and numerous animals have a large repertoire of virulence-associated factors. Although pathotypes were proposed and despite some species are more frequently isolated in human and animal infections, their pathogenicity is still poorly understood, mostly because very few comprehensive functional studies are available and because investigations taking into account the genetic diversity and the biological complexity within the genus are lacking.We assumed that for an opportunistic bacterial pathogen of environmental origin as versatile and ubiquitous as Aeromonas, the population structure in complex of species, the outstanding genetic/genomic diversity, the polymorphism of virulence factors and the interactions within pathogenic populations can act as factors driving the adaptation to a pathogenic behaviour. To test this hypothesis, we studied i) the diversification within “A. media”, a complex of species used as a model by a population study that included multilocus genetics, phylogenetics, evolutionary features, comparative genomics, as well as phenotypics, lifestyle and habitat ii) the patho-genomics of well-known virulence factors in aeromonads (aerolysin, thermolabile and thermostable enterotoxins, exotoxin A, serine protease, components and effectors of type III secretion system, and lateral flagellin) in a population that is representative of the known taxonomic diversity in the genus (30 species) and iii) the pathogenic behaviour using an in vivo model (Caenorhabditis elegans), an in vitro model (cytotoxicity, cytoadhesion, biofilm production, motility), and intercellular signals production (type I quorum-sensing) for populations involved in mixed aeromonosis, i.e. 5% of human aeromonosis defined by the isolation of at least 2 distinct clones.The phenomenon of speciation described in the complex “A. media” that aggregates 3 genomic species demonstrates that Aeromonas harbours a population structured in complexes of closely related species whose genetic and genomic diversity, as well as evolution mode (mutations and recombinations) reveal a wide adaptative and patho-adaptative potential linked to lineage emergence. Among the complex “A. media”, the species A. rivipollensis seems to be more adapted to a host-associated lifestyle and harbours specific genes for the resistance to environmental stress. Aeromonas has a wide range of virulence-associated genes, which presented diverse evolutive history. Some of them display a phylogeny linked to the core-genome evolution. These results suggest that these genes are involved in speciation processes probably related to niches adaptation. The evaluation of performances of virulence PCRs revealed major lacks of sensitivity of tested methods mainly due to the genetic polymorphism of the virulence factors. By using in vivo models and in vitro models, we also showed that Aeromonas mixed populations recovered from clinical samples could change the course of infection, likely through a cooperative or competitive mechanism that involves cell-to-cell signalling.The high complexity of Aeromonas results from its population structure, virulence factors polymorphism and multicellular behaviours. They are all putative adaptation factors to a pathogenic behaviour that may explain at least partially the difficulties encountered to elucidate pathogenicity of these bacteria
Dionne, Mélanie. „Variation génétique et potentiel d'adaptation locale chez le saumon atlantique, Salmo salar : structure de population, adaptation immunitaire et résistance aux pathogènes“. Thesis, Université Laval, 2008. http://www.theses.ulaval.ca/2008/25929/25929.pdf.
Der volle Inhalt der QuelleOne of the central endeavors in evolutionary ecology is to understand the mechanisms responsible for natural biodiversity. Biodiversity is defined as the combined diversity of ecosystems, species, populations and the genetic diversity within a given species. Even within a species, a wide diversity of phenotypes and genotypes is often observed, resulting from the interaction between natural selection, gene flow, genetic drift and mutations. The central objective of this thesis was to assess the genetic variability and evaluate the potential for local adaptation in wild Atlantic salmon, Salmo salar. Analyses of neutral molecular markers in 51 salmon rivers revealed a hierarchical genetic structure and suggested the existence of seven regional groups in Québec, Labrador and New-Brunswick, Canada. Landscape genetic analyses suggested a predominant influence of gene flow and thermal regime adaptation in maintaining genetic differentiation. Indirect evidence also suggested that immigrants from a different regional group were less successful in establishing in the new environment compared to residents. Different extents of genetic structure were also found within some river systems, questioning the river-based management approach in Atlantic salmon. Large scale genetic variability at an immuno-competence gene, the Major Histocompatibility Complex (MHC) class IIβ gene, revealed that genetic diversity increased with increasing temperature and bacterial diversity in rivers contrary to patterns with neutral microsatelite markers. This increase in MHC diversity with temperature was more pronounced at the peptide-binding region involved in pathogen binding than at other molecular sites. These results agree with the hypothesized influence of temperature-associated pathogen diversity on local adaptation in Atlantic salmon. Finally, pathogen infections in juvenile salmon were found to be more frequent at the beginning of the summer in southern rather than northern rivers, in concordance with pathogen selection pressure in the wild. A predominant and possibly introduced pathogen, a myxozoa of the genus Myxobolus, was identified in juvenile salmon and two MHC alleles were found to be associated with resistance and susceptibility to that infection, suggesting the importance of MHC standing genetic variation for facing pathogens in a changing environment. This thesis contributes to our understanding on mechanisms maintaining genetic variability and influencing local adaptation in wild Atlantic salmon through analyses in landscape genetics, genetic population structure and patterns of spatio-temporal infectivity in nature.
Thézé, Julien. „Diversification et adaptation génomique des virus entomopathogènes“. Thesis, Tours, 2013. http://www.theses.fr/2013TOUR4006.
Der volle Inhalt der QuelleAt different timescales, the purpose of my PhD was to understand insect virus evolution through the study of the genomic diversification and adaptation of insect large DNA viruses. Firstly, I was able to estimate the ages of baculovirus and nudivirus diversifications, and to propose a long-term coevolutionary scenario between these viruses and their insect hosts. Then, on a narrower timescale, I showed that insect hosts are the major factor in baculovirus diversification, and surprisingly, I also observed that the virus biotic environment, i.e. insect host plants, plays a central role in their evolution. Secondly, punctual mutations have been linked to the local adaptation of differentiated populations of the baculovirus SeMNPV. Finally, the study of convergent genomic adaptation between entomopoxviruses and baculoviruses highlighted that horizontal gene transfers are an important source of variability for large DNA viruses, for the adaption to the same ecological niches. Genes and mechanisms identified in this PhD work provide new insights to understand how genomes are shaped by ecology
Aujoulat, Fabien. „Adaptation et spécialisation des bactéries environnementales à l'infection humaine : étude des genres Ochrobactrum et Agrobacterium“. Thesis, Montpellier 1, 2012. http://www.theses.fr/2012MON13501/document.
Der volle Inhalt der QuelleThe opportunistic bacterial pathogens (OBP) cause the main part of bacterial infectious diseases. Environmental-borne OBP should encounter dramatic changes in lifestyle in order to colonize human beings. The conditions of this adaptation should precise concepts about OBP and emerging pathogens.The genera Ochrobactrum and Agrobacterium groups bacteria with versatile lifestyles that establish diverse relationships with the eukaryotic cells. These environmental-borne OBP caused diverse infectious diseases in immune-compromised patients. In this study, we undertook an approach of multilocus genetic on large population of environmental and clinical strains of Ochrobactrum and Agrobacterium. The population structures were compared to phenotypic traits related to adaptation and virulence in man, such as growth temperature, biofilm formation and virulence tested in Caenorhabditis elegans and human macrophages models.Ochrobactrum anthropi and Ochrobactrum intermedium are the two main Ochrobactrum species to be involved in human diseases. O. anthropi displays an epidemic population structure organized in two large clonal complexes (CCs). CC4 groups only human associated strains whereas CC1 contain environmental and clinical strains. Population genetics suggested that CC4 is a human-associated clone although phenotypic, genomic and virulence traits do not differ between CC1 and CC4 strains.As O. anthropi, O. intermedium displays a high genetic diversity without correlation between the genetic structure and the origin of strains. The level of genetic diversity among clinical strains appears as high as observed in the whole population. Several data such as a low level of genomic diversity suggested that O. intermedium is associated to a narrow ecological niche. The low number of environmental strains described for this species as well as an optimal growth at 37°C suggested that human beings could be the main niche for O. intermedium. Virulence in macrophage and C. elegans models showed diverse behaviour whereas some strains are able to survive and multiply in macrophages model.Multilocus genetics in a population of Agrobacterium spp. that displays diverse lifestyles, revealed a human associated population as observed for O. anthropi. The clinical genovar A7 groups 80% of the clinical strains included in the study, this strains growing at 42°C. Data obtained in this study will be confronted to the knowledge about other environmental-borne OBP such as Pseudomonas aeruginosa, Stenotrophomonas maltophilia and bacteria belonging to the species complex Burkholderia cepacia. All these bacteria displayed sub-populations associated to man or to a particular human disease. These sub-populations suggest a specialization process that will be described in the context of the speciation of bacterial pathogen in order to revisite the concept of « opportunisme infectieux »
Tollenaere, Charlotte. „Génétique et évolution du rat noir (Rattus rattus), réservoir de la peste à Madagascar“. Montpellier 2, 2009. http://www.theses.fr/2009MON20205.
Der volle Inhalt der QuelleSelective pressure applied by pathogens can lead to extremely rapid evolutionary changes on their hosts. It could be the case for the black rat (Rattus rattus), which presents populations resistant to plague (Yersinia pestis infection), where plague have been endemic since about one century, whereas low altitude zone (where the disease is absent) populations are plague susceptible. The black rat is the only possible plague reservoir in Madagascar. This work aims to study plague resistance in R. Rattus, as this trait has important consequences for the disease transmission and maintenance. Neutral genetic patterns agree with a unique colonization of Madagascar by the the black rat, 1000-2000 years ago, from Arabian Peninsula. As for humans, rat settlement would have begun by coastal regions, and latter expanded to the central highlands. Experimental work (controlled infestations and crosses) allowed the study of the resistance phenotype and its offspring transmission. Resistance level variation between plague focus and plague-free zone was confirmed and extended to other localities. Finally candidate gene and genomic approaches lead to detect genetic markers potentially undergoing divergent selection between plague focus and plague free zone than neutral loci and/or associated with experimental plague challenge issue
Saillant, Vincent. „Comprendre le mécanisme du système senseur d’hème des bactéries pathogènes, une cible antibiotique innovante A novel Enterococcus faecalis heme transport regulator (FhtR) is a heme sensor in the gastrointestinal tract“. Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASB023.
Der volle Inhalt der QuelleHeme, a porphyrin containing an iron atom, is an essential cofactor of several bacterial functions. Heme is also toxic because of the reactivity of the iron generating reactive oxygen species. One of the main mechanisms of heme detoxification, in Gram-positive bacteria, relies on the expression of a heme efflux ABC transporter, HrtBA. The regulation of this transporter has been investigated in two opportunistic pathogens, Enterococcus faecalis and Staphylococcus aureus, two bacteria responsible for multiresistant nosocomial infections. In E. faecalis, a new TetR family regulator, FhtR, has been identified and characterized. The FhtR dependent transcriptional inhibition of hrtBA is lifted by its binding to heme. FhtR controls the intracellular heme pools as showed par the activity of the endogenous heme dependent catalase, KatA. FhtR is thus a master regulator of heme intracellular homeostasis in E. faecalis. In a mouse model of intestinal transit, HrtBA is expressed, demonstrating the relevance of this system in the gastrointestinal tract where E. faecalis is a commensal resident. In S. aureus, hrtBA transcription is controled by the two-component system, HssRS. The study of the mechanism of the membrane heme sensor HssS showed that the intracytoplasmic of the histidine kinase was responsible of the binding and heme signal transduction for HrtBA expression. Alltogether, these results demonstrate that while HrtBA is conserved among Gram positive bacteria, the regulating mechanisms leading to its expression are varied. This suggests that the host heme response is dependent of the bacteria lifestyle and underlies the importance of this cofactor in the host-pathogen relationship. Inhibiting heme effux by HrtBA or the heme sensing mechanisms could lead to new antibiotic strategies
Abad, Pierre. „Aspects moléculaires des mécanismes de résistance chez Nicotiana tabacum en réponse à des agressions induites par des agents pathogènes ou abiotiques“. Paris 11, 1986. http://www.theses.fr/1986PA112289.
Der volle Inhalt der QuellePaul-Pont, Ika. „Sensibilité et adaptation de populations de bivalves marins soumis à des stress multiples : infestation parasitaire, contamination microbienne et pollution métallique“. Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14008/document.
Der volle Inhalt der QuelleIn coastal ecosystems, man-mediated activity and natural context induce a ?multistress? situation in aquatic organisms. Amongst potential perturbation sources, three of them were studied: metal contamination, bacterial infection and parasite infestation. An integrated approach of their interactions on genetic, protein, cellular and population dynamics responses in the cockle (Cerastoderma edule) and the Manila clam (Ruditapes philippinarum) was undertaken through field and laboratory studies. A two-years monitoring was conducted in four bivalve populations from different environments to estimate the fitness of populations (parameters of population dynamics), in relation with the baseline levels of stressors (metals, parasites) and with the adaptive responses implemented by bivalves in terms of detoxification and immunity. This approach allowed describing different scenarii concerning the relationship between bivalve populations and their environment. In laboratory, co-infection experiments (trematode parasite Himasthla elongata, bacteria Vibrio tapetis) were conducted on these populations in controlled condition with or without metal contamination (cadmium). They showed that the response of bivalves to stress is species-dependent. Combinations were not intuitively deduced from the "mono - stress" responses underscoring the concept of interactions. Despite the complexity and diversity of these interactions, some mechanisms predominated regardless of the studied species. While parasite infestation was not modulated by the presence of metal or bacteria in the environment, metal bioaccumulation in turn was strongly influenced by the presence of one or several pathogens. Beyond disrupting the accumulation of pollutants, the presence of pathogens interfered with the cellular detoxification mechanisms including impairment of the metallothionein (MT) synthesis. A focus on the response of MT in cockles exposed to a metal through the expression of isoform Cemt1 and protein synthesis confirmed the complementary of these observations (gene and protein). They also highlighted the need to analyze responses at different scales to obtain an overview of existing interactive process between pollutants and pathogens. Strong interactions were found: ?Cd x parasite? in the cockle and" bacteria x parasite "in the clam, at the genetic, protein and immune levels. Finally, these experiments highlighted the important role of life history on the sensitivity of organisms to pollutant-pathogen interactions