Дисертації з теми "Interaction hôte agent pathogène"
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He, Le. "Interactions hôte-pathogène entre Caenorhabditis elegans et le champignon Drechmeria coniospora." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4080/document.
We have successfully adapted a PEG-mediated transformation protocol for D. coniospora. Together with the ccdB and Gibson based plasmid construction method, we established a system to genetically manipulate this fungus which serves as an important tool for host-pathogen interaction study. We identified the specific pathogenic lifestyle of D. coniospora based on its genomic sequence. Comparative genomic analysis revealed a list of potential fungal effectors which engage with the host immunity, for instance SapA (G3895). We further constructed a reporter strain for SapA and identified its host target SPP-5, an antimicrobial peptide. Our study focusing particularly on the pathogen provides an insight for the host-pathogen interaction between C. elegans and D. coniospora. Despite the successful generation of 5 D. coniospora transgenic strains. Nevertheless, the remaining problems such as multiple transferring during protoplasts preparation and slow growth of D. coniospora after transformation still need to be resolved. One of the solutions is to substitute the general medium with a medium resembling the host environment.We show that D. coniospora SapA protein interacts with worm immune effector, SPP-5 in vitro indicating its potential role to suppress the host immunity. Due to the fact that SapA is also highly expressed at the late stage of infection, we cannot rule out the other possible functions of this protein. We could employ Mass spectrometry technique to identify other host proteins which interact with SapA in vivo
Cellier, Mathieu. "Elaboration de modèles expérimentaux pour l'étude des stress cellulaires dans les interactions hôte - agent pathogène." Montpellier 2, 1992. http://www.theses.fr/1992MON20205.
Ayach, Maya. "Interaction hôte-pathogène : mécanisme d’inhibition de la synthèse protéique humaine par la protéine circumsporozoïte de Plasmodium falciparum, agent du paludisme." Strasbourg, 2011. http://www.theses.fr/2011STRA6100.
During my PhD, I was concerned by the study of the host-parasite interaction and its consequences on protein synthesis in human and Plasmodium falciparum (parasite responsible of the malaria) respectively. I have developed two major aspects : (i) The study of the aminoacylation reaction of transfer RNA and thus by comparison of human and parasite systems and (ii) the understanding of the mechanism of inhibition of protein synthesis in human by the Circumsporozoite protein of the parasite, a transmembrane protein which is secreted during the parasite infection of host hepatocytes. The plasmodial cytosolic tyrosyl-tRNA synthetase is a classical synthetase concerning its structural organization. It possesses two functional domains, catalytic domain and tRNA binding one. The kinetic characteristics of the aminocylation reaction (Km, Kcat and plateau) were determined. I have clearly shown that plasmodial TyrRS animoacylates both transcripts of plasmodial and human tRNATyr with the same efficiency. On the other hand, only a small fraction of modified human tRNATyr was aminoacylated by the parasite enzyme. These results indicate that crossaminoacylation reactions between the parasite and human are possible, but their efficiency varies from one system to another. Concerning the apicoplastic TyrRS, this enzyme, at the opposite of the cytosolic one, it presents two insertions. These insertions are characteristic of some parasite proteins and are called LCR (Low Complexity Region). The presence of such sequences in the apicoplastic TyrRS but also in other parasite proteins makes their expression in heterologous systems a difficult obstacle in the study of the parasite. During my PhD work, I did participate to the collaboration of a new hypothese concerning the function and the role of these insertions in the production of soluble proteins. These LCRs play a key role in the co-translational folding of the parasite proteins. Finally, the big part of my work concerns the study of consequence of the host-parasite interactions on protein synthesis in human liver cells during the hepatic stage of the infection. During this stage, the parasite is covered by a transmembrane protein called the Circumsporozoite protein (CSP). Previous study in 1997 showed that CSP is secreted by the parasite, and co-localizes with endoplasmique reticulum where it does probably inhibit host translation. I have demonstrated by using rabbit reticulocytes lysate, that CSP inhibits efficiently translation and that by inhibiting the formation of pre-initiation complex 48 S. This inhibition involves a direct interaction between the CSP and the small ribosomal particle 40 S. This work shows for the first time that parasites, like some virus, could affect directly host protein synthesis. My work is part of large project concerning the study of hepatic stage of the infection; in this manuscript I will discuss the role and the consequences of such translation inhibition on the parasite life cycle
Burette, Mélanie. "Etude de la réplication intracellulaire et de la persistance de Coxiella burnetii, agent pathogène de la Fièvre Q." Thesis, Montpellier, 2020. http://www.theses.fr/2020MONTT053.
Intracellular replication and persistence strategies of the Q fever pathogenCoxiella burnetiiCoxiella burnetii is the causative agent of human Q Fever, considered as one of the most relevant re- emerging zoonosis in Europe. C. burnetii infects humans through the inhalation of contaminated aerosols, causing epidemics with serious economic and health consequences. Following internalisation, C. burnetii subverts host cell functions to inhibit the innate immune response and generate a replicative niche called CCV (Coxiella-containing vacuole) characterised by a unique protein and lipid composition. My thesis project focuses on the study of the host/pathogen interactions underlying the persistence and intracellular replication of C. burnetii.First, the function of the effector protein NopA was discovered showing how this protein inhibits the innate immune response in infected cells. The results obtained during my PhD have shown that NopA interacts with Ran and triggers an imbalance in its nucleocytoplasmic gradient, thereby perturbing the nuclear import of eukaryotic proteins and the expression of pro-inflammatory cytokines. In parallel, the role of lipid metabolism in the establishment of the CCV was investigated. By using a wide array of lipid probes and confocal microscopy, the lipid signature of CCVs was determined and revealed that PI(4)P and LBPA are actively subverted by C. burnetii during infection. Lipid pulldown assays then led to the identification of C. burnetii candidate effector proteins interacting with host cell lipids. One of them, CBU0635, is a putative phosphoinositide phosphatase that diverts the secretory pathway to the forming Coxiella- containing vacuole while CBU2007 manipulates lysobisphosphatidic acid metabolism to recruit the ESCRT machinery and block the biogenesis of multivesicular bodies. These results help to better understand intracellular replication and persistence strategies of C. burnetii and could allow the development of new antimicrobials and the therapeutic repurposing of C. burnetii proteins
Cesbron, Sophie. "Interaction entre des mutants hrp d'Erwinia amylovora, agent du feu bactérien, le parent pathogène et la plante hôte : recherche de mécanismes modulant la compatibilité." Phd thesis, Université d'Angers, 2009. http://tel.archives-ouvertes.fr/tel-00455109.
Delaunay-Cesbron, Sophie. "Interaction entre des mutants hrp d'Erwinia amylovora, agent du feu bactérien, le parent pathogène et la plante hôte : recherche de mécanismes modulant la compatibilité." Angers, 2009. http://www.theses.fr/2009ANGE0017.
Erwinia amylovora is the causal agent of fire blight, a disease that affects Maloideae. This gammaproteobacteria requires a type three secretion system (T3SS) for its pathogenicity. Previous work has shown that avirulent hrp mutant strains of E. Amylovora affected in regulatory functions (hrpL and hrpS) protect apple seedlings from developping fire blight symptoms. We investigated molecular mechanisms leading to this protection. In a first part of our work, we studied molecular responses of the protected plant, according to major defense pathways (salicylic acid, jasmonic acid, ethylene) and in the phenylpropanoid pathway. Results show that none of these pathways is particularly induced by Ea hrpL or Ea hrpS mutants. Then, the hypothesis of a direct effect of mutants on the wild type strain has been denied. We tried to trace differential transcripts and proteins between these bacteria through targeted and global approaches (targeted genes vs cDNA-AFLP). Results show that HrpL and HrpS are able to differentially regulate other genes that hrp genes : HrpL negatively regulates flagellar system, chemotaxis and genes related to GSP, and positively regulates one gene of T1SS and one OMP ; HrpS negatively regulates quorum sensing and positively regulates one gene implicated in the synthesis of ethylene. We were particularly interested in flagellar system of E. Amylovora. An in silico analysis of flagellar genes led to the discovery that E. Amylovora possesses two flagellar systems with distincts flagellins (32 vs 50KDa). The 32KDa flagellin, overexpressed in hrpL mutant, does not display the flg22 peptide classically implicated in elicitation and is not necessary for protection. On the whole, our work does not entirely explain the origin of the plant protection, induced by regulatory hrp mutants, nevertheless it provides new key information on E. Amylovora and on the regulation of several genes during the interaction with the host plant
Barbosa, Cavalcante Maria de Jesus. "Imagerie cellulaire de l'interaction Musa acuminata : mycosphaerella fijiensis." Montpellier SupAgro, 2009. http://www.theses.fr/2009NSAM0031.
Consentino, Laurent. "Mécanismes d'acquisition du fer de l'hôte chez Bacillus cereus : rôle du couple bacillibactine-FeuA et expression des gènes impliqués dans l'homéostasie du fer in vivo durant l’infection intestinale chez l’insecte." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLA018/document.
Iron acquisition is essential for most living organisms, including many pathogenic bacteria. However, free iron is toxic: it is bound into storage or transport proteins (e.g. ferritin, hemoproteins…) and iron homeostasis is tightly regulated. To scavenge iron from these sources, bacteria possess several systems to acquire the bound iron, by surface proteins or siderophores. Bacillus cereus is a sporeforming Gram-positive bacterium, opportunistic human pathogen, 2nd cause of food-borne disease in France. It has been demonstrated that the B. cereus surface protein IlsA and the siderophore bacillibactin (BB) are involved in iron acquisition from ferritin and that these two molecules are important for infection of the insect model G. mellonella. My thesis project focused on two parts: first the study of the BB-Fe3+ complex import into the cell by the siderophore binding protein FeuA highlights the central role of both BB and FeuA. The deletion of the genes encoding for these two molecules limits iron acquisition by B. cereus from ferritin, heme, hemoglobin and inorganic iron in vitro. On the other hand, the virulence phenotype during intra-haemocelic infection of G. mellonella is similar to the Wild-type strain. These results suggest a possible feedback on the expression of virulence factor genes when B. cereus is unable to synthetize both BB and FeuA, and therefore are under high stress. The second part of my work focused on the expression of genes involved in iron homeostasis in vivo, during gut infection of germ-free larvae of G. mellonella. We chose to perform a microgenomic approach, using laser-capture microdissection to get small samples in targeted areas, and then analysing the expression of chosen genes by RT-qPCR and ddPCR at two time points post ingestion The results show that : i) the colonisation of G. mellonella gut is impacted when B. cereus is deprived of both BB and FeuA ; ii) ilsA is expressed during gut infection ; iii) iron homeostasis is involved in adaptation and pathogenicity from the early step of infection of the insect gut ; iv) only weak gene expression modulation occured between the two timepoints This work gives new fundamental knowledge about B. cereus iron homeostasis, and highlights the use of new techniques regarding the in situ study of host-pathogen interactions
Baurès, Isabelle. "Caractérisation moléculaire de l’éliciteur et analyse des partenaires requis pour la résistance à des virus contrôlée par le gène Rx de pomme de terre chez les plantes cultivées." Thesis, Evry-Val d'Essonne, 2008. http://www.theses.fr/2008EVRY0001.
In potato, the resistance gene (Rx) encodes a protein that confers resistance against Potato virus X (PVX). The trigger of the resistance is the recognition of PVX coat protein (CP). The mechanisms of this resistance are not well understood. In this project we investigate two different aspects of this interaction. The first goal of this project is to characterize the CP elicitor. In the first approach we mutagenized key amino acids in the PVX CP and showed that the affinity between elicitor and receptor modulates the intensity of the Rx response. In the second approach we showed that other viruses related to PVX with natural sequence variations in the CP are able to induce Rx mediated resistance. The second goal of this project is to identify genes required for Rx mediated resistance a collection of EMS mutants tomato (cv Micro-Tom) carrying the Rx gene has been generated and screened for restored susceptibility to PVX. Three mutants were identified and characterized
Blisnick, Adrien. "Caractérisation de IrSPI, un inhibiteur de sérine protéase impliqué dans la prise du repas sanguin et l’infection bactérienne des tiques Ixodes ricinus." Thesis, Paris, Institut agronomique, vétérinaire et forestier de France, 2019. http://www.theses.fr/2019IAVF0005/document.
Ixodes ricinus tick species, the most abundant and widespread tick in Europe, is an important vector of pathogens affecting both animal and human health. To replace the use of acaricides that generate environmental contamination and resistances, new environmentally sustainable approaches providing broad protection against ticks and tick-borne pathogens (TBP) are urgently needed. Such development requires improved understanding of the biology of ticks and more particularly of their interactions with vertebrate hosts and TBP. Tick saliva is an essential biofluid for ticks, as its proteolytic, anticoagulant, immunomodulatory, analgesic and anti-inflammatory activities allow ticks to acquire their blood meal under optimal conditions. Moreover, injection of saliva during blood feeding represents the principal route by which TBP are transmitted to the host. To understand the molecular mechanisms involved in TBP transmission, as well as to identify putative vaccine candidates against I. ricinus, salivary glands from bacteria infected and uninfected ticks were previously compared by high throughput transcriptomics. The most up-regulated transcript following infection was IrSPI, which belongs to the Kunitz/BPTI inhibitor family. Functional analyses via RNAi knockdown experiments revealed that IrSPI enhances both blood feeding and bacterial burden in the salivary glands. This present PhD work concerns then the structural, biochemical and functional characterization of IrSPI as a molecule involved in tick-host-pathogen interactions. Our aim was first to define the structure of IrSPI gene but, unfortunately, while our results have led to progress on this issue, we have not been able to get the full sequence. Then, the dynamic of IrSPI expression was evaluated during both tick feeding and colonization of ticks by pathogens, showing that its expression is induced by blood feeding and TBP but not by Escherichia coli that is not transmitted by I. ricinus. In addition, our results shown the expression of IrSPI in several tick organs, suggesting its implication in several functions in tick physiology. Among them, the discovery of the injection of IrSPI, through the saliva, to the vertebrate host allowed us to consider a role in host responses to tick bite. Evaluation of IrSPI effect on host showed no impact on coagulation through extrinsic pathway, as determined by analysis of thrombin generation time and by fibrinolysis, or in angiogenesis. However, it inhibited the proliferation of mitogen-stimulated CD4+ lymphocytes and increased unstimulated-B cell proliferation. In addition, IrSPI also modulated cytokine production from macrophages and splenocytes, repressing significantly most of proinflammatory cytokines and chemokines. Thus, we demonstrated that IrSPI plays a role in modulating the host immune response during blood feeding. Finally, preliminary results in the identification of the protein’s interactants open many research perspectives for understanding how IrSPI acts in tick physiology and counteracts host responses to tick injury and pathogen transmission
Hatsch, Didier. "Interaction hôte/pathogène:étude du modèle Humulus lupulus/Fusarium graminearum : Identification,génomique et transcriptomique du pathogène." Université Louis Pasteur (Strasbourg) (1971-2008), 2004. https://publication-theses.unistra.fr/public/theses_doctorat/2004/HATSCH_Didier_2004.pdf.
Fusarium graminearum is a pathogen of first importance for cereal crops. This species is not described as a hop (Humulus lupulus L. ) pathogen, however it was found in Alsace on this plant during decay episodes. An identification method of the species of the genus Fusarium based on the cellobiohydrolase-C and combining CAPS (Cleaved Amplified Polymorphic Sequence) analysis and western blot has been developed. This method allows the quick and reliable identification of 11 species of Fusarium. We investigated another molecular marker: the topoisomerase II. These two novel markers showed a better accuracy in the determination of Fusarium species than the rDNA. Through a genomic strategy, 22 genes coding putatively for xylanases were predicted and validated. A transciptomic approach, allowed the determination of gene expression profile of the predicted genes and underlined the major implication of 4 xylanases in cell wall degradation. The construction and random sequencing of a subtractive suppressive library highlighted several CWDE (Cell Wall Degrading Enzymes) and confirmed the implication of the major xylanases in the degradation of plant cell walls. Moreover gene candidates putatively implicated in pathologies have also been revealed. This work is a first step in the study of the Humulus lupulus / Fusarium graminearum system as a model. The two novel molecular markers allow a new insight in fungal communities on hop plants. The identification of CWDE putatively implicated in pathologies will lead to the design of inhibitors in order to understand and control the pathological process
Vigneux, Fabienne. "Interaction hôte-pathogène : apoptose induite par une nouvelle cytotoxine secrétée par la bactérie entomopathogène "xenorhabdus nematophila"." Montpellier 2, 2005. http://www.theses.fr/2005MON20173.
Vodovar, Nicolas. "Analyse génétique et génomique de l' interaction entre Drosophila melanogaster et Pseudomonas entomophila." Paris 6, 2005. http://www.theses.fr/2005PA066366.
Varela, Chavez Carolina. "Caractérisation fonctionnelle d’une cyclomoduline pro-apoptotique nommée Cif (Cycle Inhibiting Factor) chez les bactéries entomopathogènes du genre Photorhabdus." Montpellier 2, 2009. http://www.theses.fr/2009MON20183.
Pourpre, Renaud. "Caractérisation de protéines nucléaires ciblées par la bactérie pathogène Listeria monocytogenes." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS394.
Listeria monocytogenes is an optional intracellular pathogen responsible for a severe foodborne infection called listeriosis. The study of the cellular infection process of this bacterium has shed light on various mechanisms involved in host-pathogen interactions and in the functioning of the eukaryotic cell. In particular, L. monocytogenes has emerged as one of the pioneering models in the discovery of microbial targeting of chromatin and nuclear regulators. The study of a virulence factor of L. monocytogenes, LntA, allowed the identification of one of these regulators : BAHD1. By recruiting proteins involved in the formation of heterochromatin, such as HDAC1/2 and HP1, BAHD1 stimulates the formation of a compact chromatin with a repressive effect. When epithelial cells are infected with L. monocytogenes, BAHD1 suppresses the immune response stimulated by interferons, a function inhibited by LntA. Since BAHD1 is still under-researched, the first objective for my thesis was to further characterize this epigenetic regulator. In addition, preliminary data suggested that a recently discovered virulence factor of Listeria, InlP, had the potential to be, like LntA, a nucleomodulin. My second objective was to explore this hypothesis.The results of my first axis show that BAHD1 interacts with MIER1 and that this interaction is crucial for the association of BAHD1 with HDAC1/2. We also report that BAHD1 modifies chromatin by changing histone methylation and acetylation, as well as DNA methylation, at a target gene, ESR1. These results allow us to propose that BAHD1 form, with MIER1, a scaffold assembling a new chromatin remodeling complex associated with HDAC1/2 : the BAHD1 complex. We then studied the role of BAHD1 in an organ targeted by Listeria, the brain. Our results indicate that a total deficiency in BAHD1 alters the overall transcriptome of this organ in mice. Most of the overexpressed genes are involved in nervous system functions, metabolism and neurological disorders. The predominantly downregulated genes are involved in innate immunity pathways, including interferon response genes. In addition, a haplodeficiency in Bahd1 causes behavioral problems. Compared to Bahd1+/+ mice, Bahd1+/- mice suffer from increased anxiety and changes in acoustic startle reflex. These results suggest that deregulation of BAHD1, through environmental or infectious stimuli, may have neuro-pathological effects.The second axis of my thesis focused on the study of InlP interactions with host nuclear proteins, identified by a double-hybrid screen. First, we show that InlP is an atypical internalin, with leucine-rich repeats characterized by an LPX2 motif. We then identify two nuclear proteins targeted by InlP: the splicing factor and tumor suppressor RBM5 and the corepressor RERE. When InlP is produced ectopically in human cells, it is localized in the nucleus, where it alters the formation of nuclear bodies enriched in RERE. In RBM5-overexpressing cells, InlP inhibits the pro-apoptotic effect of RBM5 and stimulates the formation of dense nuclear bodies associated with RBM5. These results suggest that InlP is a nucleomodulin acting on the assembly and disassembly of target protein storage compartments involved in the synthesis and splicing of host RNAs.This work opens perspectives in the understanding of host-pathogen interactions and in a better knowledge of patho-epigenetic mechanisms, as well as in cell biology and the understanding of membraneless nuclear organelles dynamics
Duperthuy, Marylise. "Effecteurs moléculaires de lassociation Crassostrea gigas / Vibrio splendidus. Rôle de la porine OmpU dans les mécanismes de résistance et déchappement à la réponse immunitaire de lhôte." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20060.
Vibrio splendidus LGP32 is a bacterial pathogen associated to the summer mortality outbreaks that have affected the production of Crassostrea gigas oysters over the past decades. We showed here that the OmpU porin is a major effector of the V. splendidus / C. gigas interaction. For that, we have constructed a ΔompU mutant of V. splendidus, and shown that the OmpU porin is implicated (i) in the resistance of V. splendidus to antimicrobials, including those of oyster, (ii) in its in vivo fitness, and (iii) in its virulence in oyster experimental infections (mortalities have been reduced from 56 % to 11 % upon mutation). In agreement, we have shown that the ompU deletion modified the expression of secreted proteins controlled by the virulence (ToxR) and the membrane integrity (SigmaE) regulation pathways. Furthermore, we have shown that OmpU has a major role in the recognition of V. splendidus by oyster hemocytes. Indeed, (i) in vivo, hemocyt e genes displayed differential responses to an infection with the wild-type or the ΔompU mutant, and (ii) in vitro, OmpU was necessary for hemocyte invasion by V. splendidus. This invasion process required the hemocyte b-integrin and the oyster plasma extracellular SOD, which was found to act as an opsonin recognizing OmpU. Thus, OmpU is a major virulence factor that allows infection of hemocytes in which V. splendidus is able to survive by inhibiting the production of reactive oxygen species and the formation of acidic vacuoles. Resistance of V. splendidus to hemocyte antimicrobials, which is also OmpU-dependant, is probably an additional determinant of V. splendidus intracellular survival
Golovkine, Guillaume. "Franchissement des barrières épithéliales et endothéliales par le pathogène opportuniste Pseudomonas aeruginosa." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAV009/document.
P. aeruginosa is one of the main pathogens responsible for nosocomial infections. Acute infections by this bacterium are associated with high rates of morbidity and mortality, especially when bacteria disseminate in the bloodstream. In most situations, blood infection is the consequence of the crossing of two essential tissue barriers by P. aeruginosa: the epithelium for the mucosa and the endothelium for the blood vessel. Although these events are critical steps for systemic spread of bacteria, the mechanisms involved in the penetration of the pathogen in the organism are poorly understood. For the endothelium, we demonstrate that P. aeruginosa induces the cleavage of VE-cadherin, a protein of endothelial junctions, by the action of LasB, a protease secreted by the bacteria. VE-cadherin cleavage induces a loss of integrity of the endothelium, allowing bacterial access to the cellular basolateral domain. Once in this location, the Type 3 secretion system may inject toxins into the cell, triggering a major intoxication process. Crossing of the epithelial barrier involves a very different mechanism. Using real-time confocal microscopy, we show that P. aeruginosa uses a paracellular route to transmigrate, exploiting junctional weaknesses at sites of cell division and cell death. This transmigration process requires the coordinate actions of Type IV pili, the flagellum and toxins of the Type 3 secretion system
Bellini, Valeria. "Toxoplasma gondii : approches moléculaires (mutants knocked-out) pour l'étude de la fonction des protéines des granules denses dans l'interaction hôte-parasite." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAV019/document.
Toxoplasmosis, which is caused by the intracellular parasite Toxoplasma gondii is characterized by a life-long chronic infection. The parasites replicate inside a parasitophorous vacuole (PV), which evolves into a persistent cyst. The molecular mechanisms governing the differentiation process are poorly characterized. It is known that the dense granules proteins (GRA) are major components of both the PV and the cyst wall, enabling their interaction with the host cells. Using a Prugniaud cystogenic type II strain in which the gra5 gene was invalidated and a combination of cellular and proteomic approaches, we discovered that GRA5 regulates i) the molecular content of the PV, ii) the PV interaction with the host endoplasmic reticulum and iii) host cell homeostasis,that is necessary to ensure the formation of a stable cyst wall
Vanhove, Audrey. "Survie intracellulaire, effets cytopathiques et virulence de Vibrio tasmaniensis LGP32, pathogène de l’huître Crassostrea gigas." Thesis, Montpellier 1, 2014. http://www.theses.fr/2014MON13518.
Vibrio strains belonging to the Splendidus Clade have been repeatedly found in juvenile diseased oysters affected by summer mortalities. V. tasmaniensis LGP32 is an intracellular pathogen of oyster hemocytes which has been reported to alter the oxidative burst and inhibit phagosome maturation. We show here that LGP32 behaves as an intravacuolar pathogen that survives within large cytoplasmic vacuoles. LGP32 induces cytotoxic effects such as membrane disruptions and cytoplasmic disorders. Cytotoxicity was shown to be entirely dependent on LGP32 entry into hemocytes. Moreover, LGP32 releases outer membrane vesicles (OMVs) inside the phagosome. LGP32 OMVs were found to be protective against host defenses and to serve as vehicles for the delivery of LGP32 virulence factors to oyster immune cells. Indeed, OMVs conferred a high resistance to antimicrobial peptides. They also displayed a high content in hydrolases (25 % of total proteome) among which a serine protease, named Vsp for vesicular serine protease, was found to be specifically secreted through OMVs. Vsp was shown to participate in the virulence phenotype of LGP32 in oyster experimental infections but did not degrade AMPs entrapped in OMVs. By developing a transcriptomic approach, we identified a series of Vibrio antioxidant and copper efflux genes whose expression is strongly induced within oyster hemocytes. Construction of isogenic deletion mutants showed that resistance to reactive oxygen species and copper efflux are two important functions required for LGP32 intracellular survival, cytotoxic effects and virulence. Their high conservation among vibrios suggests they could contribute to intracellular survival of other Vibrio species
Manzoni, Giulia. "Malaria liver infection : entry pathways for Plasmodium sporozoites." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066676.
Plasmodium sporozoites are transmitted by Anopheles mosquitoes and first infect the liver where the parasite replicates as a pre-requisite to the development of the pathogenic blood stage infection. Sporozoites infect hepatocytes by forming a parasitophorous vacuole differentiating into liver stages. Invasion involves parasite and host proteins but the underlying mechanisms remain unknown. To facilitate monitoring of sporozoite invasion, we generated novel transgenic fluorescent parasites, using a new selection strategy termed GOMO (Gene Out Marker Out). Using fluorescent P. yoelii strains and a robust cellular system we further characterized the temporal and molecular mechanisms of sporozoite invasion. We document that sporozoite productive invasion is preceded by a phase of cell traversal, and show that during cell traversal sporozoites enter transient vacuoles, which are distinct from parasitophorous vacuoles. We also uncovered that the perforin-like protein mediates sporozoite egress from transient vacuoles and escape from degradation by the host cell lysosomes. We studied the role of host factors implicated during the productive invasion of rodent and human Plasmodium species. We knew that P. falciparum and P. yoelii sporozoites require CD81 for infection and that P. berghei and P. vivax can infect cells lacking CD81. We identified two members of CD36 superfamily, SR-BI and CD36, as host entry factors defining a CD81-independent entry route. These results pave the way toward the elucidation of the mechanisms of sporozoite invasion and the identification of parasite ligands that mediate host cell entry, which would constitute potential targets for a malaria vaccine
Montarry, Josselin. "Réponse adaptative des populations de Phytophthora infestans, agent du mildiou de la pomme de terre, au déploiement en culture de son hôte Solanum tuberosum." Phd thesis, Agrocampus - Ecole nationale supérieure d'agronomie de rennes, 2007. http://tel.archives-ouvertes.fr/tel-00133363.
Brelle, Solène. "Phosphorylation et interaction hôte/pathogène : analyse de deux facteurs bactériens sécrétés, la kinase CstK de Coxiella burnetii et la phosphatase PtpA de Staphylococcus aureus." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS094/document.
Bacterial pathogens have developed diverse strategies towards host signalling pathways, in order to subvert the immune response and/or create permissive niches for their survival. One such strategy is based on the secretion of bacterial signalling proteins into the target host cells, thereby directly modulating the status of host signalling networks. Because the mechanisms involved are largely intractable to most in vivo analyses, very little is known about the signals, sensors, and effectors mediating these adaptations. Sensing the host environment is a key component to execute appropriate developmental programs, and the eukaryotic-like phosphosignaling systems in prokaryotes are emerging as equally important regulatory systems as the well-known eukaryotic systems, but the study of their functions is still in its infancy. The innovative aspect of this project resides in the study of the emerging role of secreted Ser/Thr kinases and phosphatases in the control of host-pathogen interactions thus modifying the global host response during infection. During my thesis, I first investigated the role of a novel bacterial protein kinase identified in Coxiella burnetii that we named CstK (Coxiella serine threonine Kinase). C. burnetii, the etiological agent of the emerging zoonosis Q fever, subverts host cell defenses, permitting its intracellular replication in specialized vacuoles within host cells. Secretion of a large number of bacterial effectors into host cell is absolutely required for rerouting the Coxiella phagosome. We demonstrated that this putative protein kinase identified by in silico analysis of the C. burnetii genome is able to autophosphorylate and undergoes in vitro phosphorylation. Moreover, we identified specific host cell proteins interacting with CstK, by the use of the model amoeba Dictyostelium discoideum, an eukaryotic professional phagocyte amenable to genetic and biochemical studies. In the second part of my project, I was interested in the role of a putative secreted protein tyrosine phosphatase (PtpA) during Staphylococcus aureus infection. Well-known in hospital-acquired diseases, this bacteria produces multiple virulence factors that lead to various severe diseases, and the increase of multi-resistant strains is a major concern. This pathogen has the ability to invade and persist in a number of different human host cell types, secreting effector proteins to modulate cellular responses. Here we demonstrated that PtpA is secreted during the bacterial growth. We also determined that PtpA presents a tyrosine phosphatase activity that is regulated by the tyrosine protein kinase CapA1B2 of S. aureus. At last, using the D. discoideum model, we identified some host proteins that interact with PtpA, but their link with infection still remain to be studied
Wong, Sak Hoi Joanne. "Caractérisation fonctionnelle de CLSTE12, un facteur de transcription impliqué dans la régulation du pouvoir pathogène Colletotrichum lindemuthianum, agent fongique responsable de l'anthracnose du haricot." Toulouse 3, 2007. http://www.theses.fr/2007TOU30070.
STE12-like proteins are transcription factors that regulate invasive growth in Saccharomyces cerevisiae and pathogenicity in parasitic fungi. These proteins harbour a homeodomain involved in DNA binding. In filamentous fungi, an additional domain is found, containing a couple of C2H2/Zn2+ fingers, whose role is unknown. Recently, a STE12-like gene (CLSTE12) was isolated from the fungal bean pathogen, Colletotrichum lindemuthianum. Gene expression studies revealed the presence of two mRNAs, resulting from the alternative splicing of an exon. The skipping of the exon leads to the deletion of one zinc finger in the corresponding protein. At the onset of pathogenesis, both transcripts were induced rapidly, then the expression level of the shorter transcript suddenly decreased during the formation of a specialized infection structure -the appressorium-, whereas that of the full-length transcript remained high. .
De, Decker Sophie. "Approches multifactorielles pour l'étude d'interactions entre l'huître creuse Crassostrea gigas et deux Vibrio pathogènes, V. splendidus et V. aestuarianus : épidémiologie, variabilité de la sensibilité de l'hôte et pathogenèse." Phd thesis, Université de La Rochelle, 2010. http://tel.archives-ouvertes.fr/tel-00556612.
Juan, Pierre-Alexandre. "Identification du système de transformation naturelle de Legionella pneumophila." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10315.
Under certain growth conditions, some bacteria are able to develop a « competence » state for natural transformation, that is, to express a panel of genes involved in the assembly of a DNA uptake system that allows bacteria to take up and recombine free exogenous DNA, leading to a genetic and phenotypic transformation. Natural transformation may have played a role in the evolution of the L. pneumophila genome.Thus, the main objective of this work was to describe the main components of the L. pneumophila DNA uptake system and to investigate its role regarding the host-pathogen interaction. Transcriptomic analysis and directed mutagenesis permitted to identify the main components of the system which is not involved in bacterial virulence. The system include a transformation pilus that is a structure frequently found in transformable species. The role of the structural protein MreB has also been investigated.By describing a first model of the natural transformation system of L. pneumophila, this work paves the way to a deeper analysis of the system dynamics and, more generally, to a better understanding of natural transformation in Gram-negative species
Lucas, Cécily. "Rôle de l'autophagie dans la réponse de l'hôte suite à l'infection par des Escherichia Coli producteurs de colibactine isolés de patients atteints d'un cancer colorectal." Thesis, Université Clermont Auvergne (2017-2020), 2018. http://www.theses.fr/2018CLFAS016/document.
Several studies have shown a role of intestinal microbiota in CRC etiology, which is the third cause of death by cancer in the world. Especially, colonic mucosa of CRC patient is abnormally colonized with E. coli strains which often carry the pathogenic pks island, leading to the synthesis of a genotoxin called by colibactin. Colibactin-producing E. coli strains induce DNA double strand breaks, chromosomic aberration and senescence in host cells enhancing the cellular proliferation and tumorigenesis in mouse models of CRC. The aim of this study is to investigate the role of autophagy, a key process in cellular homeostasis, in host defense against infection by pks-harboring E. coli (E. coli/pks+). We showed the increased expression of different autophagy-related genes in the mucosa of CRC patients colonized with E. coli/pks+ compared to that of patients colonized with E. coli without the pks island. In vitro and in vivo, we showed that autophagy is activated in intestinal epithelial cells upon infection in order to limit the pro-tumoral effects of E. coli/pks+. In a murine model of CRC, the ApcMin/+ mouse model, deficient for the Atg16l1 autophagy gene specifically in intestinal epithelial cells, we have shown a complex role of autophagy in colorectal carcinogenesis. Indeed, in uninfected conditions, autophagy plays a pro-tumoral role. However, following infection with the E. coli/pks+ 11G5 strain, mice deficient for autophagy exhibit increased tumorigenesis, accompanied by increased DNA damage, cell proliferation, and inflammation. These results suggest that autophagy is necessary to inhibit the pro-tumoral effects of E. coli/pks+ strains and thus limit the colorectal carcinogenesis induced by the latter. Future works using mouse models of CRC are required to study the role of autophagy in colonic tumorigenesis suppression following infection with E. coli/pks+. Different mechanism such as inhibition of cellular proliferation and immune response, modification of the composition of the gut microbiota will be analyzed. Together, those results will highlight the role of autophagy as a host defense mechanism against the pro-tumoral effects of pks-harboring E. coli strains. This work could also open the door to new therapeutic options in the treatment of CRC and therefore have a great impact on public health
Delevoye, Cédric. "Identification de protéines sécrétées par Chlamydia et étude fonctionnelle d'une protéine insérée dans la membrane de la vacuole, à l'interface entre les bactéries et leur hôte." Paris 11, 2006. http://www.theses.fr/2006PA112017.
Chlamydiae are obligate intracellular pathogens of humans and animals. Depending on the species, they are responsible for ocular and genital infections, and respiratory diseases. After inducing their own entry, the bacteria develop in a membrane-bound compartment, called the inclusion. During the infectious cycle, they translocate a subset of proteins via a type three secretion (TTS) apparatus into the host cytosol. Among these, the Inc proteins remain anchored in the inclusion membrane where they face the host cytosol. My work has focused on bacterial proteins secreted into the host cell. By a global approach, we have identified 24 new proteins secreted by the TTS apparatus of Chlamydia. This work has opened the functional studies of these bacterial proteins that are in contact with the host cell cytosol. More specifically, we have studied the function of an inclusion protein, IncA. We have shown that IncA, from different chlamydial species, share structural and functional homologies with the SNARE family of eukaryotic proteins, which are essential factors for cellular membrane fusion events. We have shown that IncA interact with SNAREs in both a cellular and an in vitro model. Moreover, in liposome fusion assays, IncA inhibit membrane fusion induced by a cognate SNARE complex specific from the late endosomal compartment. We propose that IncA, by mimicking SNAREs proteins, participate in the control of the interactions between the inclusion membrane and intracellular compartments of the host cell
Gazanion, Elodie. "Activité ambivalente du nicotinamide chez le parasite Leishmania : adjuvant thérapeutique dans le traitement des leishmanioses et précurseur majeur du NAD+ chez le parasite." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20191.
Nicotinamide is a vitamin provided by food that is already used in human therapy. In Leishmania protozoan parasites, this molecule shows toxic activity against parasites and has synergistic activity with antimonials, the main drugs used to treat leishmaniasis. By investigating the mode of action of this cheap vitamin, we discovered that nicotinamide is in fact the main precursor of NAD+ synthesis in Leishmania, a redox cofactor essential for all living cells. Leishmania are indeed devoid of a de novo NAD+ pathway and must synthesize it by scavenging precursors from their environment (nicotinamide, nicotinic acid and nicotinamide riboside). This NAD+ auxotrophy reveals a mixed pattern of activity of nicotinamide in Leishmania, i.e. toxic at high concentrations but also essential for parasite survival through its role in NAD+ synthesis. All enzymes of the Leishmania NAD+ salvage pathway were then identified from genome databases. We focused on a putative nicotinamidase, which has no homolog in mammals and governs the conversion of nicotinamide to nicotinic acid, the first step in the NAD+ salvage pathway. Since this enzyme could be considered as an attractive therapeutic target to develop specific parasite inhibitors, we performed a functional analysis of the corresponding gene. Targeted deletion of the nicotinamidase encoding gene induced a marked drop in parasite NAD+ content and a phenotype with strongly delayed growth. Additionally, these mutants are unable to establish durable infections in mice. The crystal structure of the nicotinamidase from L. infantum will allow us to develop specific inhibitors against this new therapeutic target
Miot, Sandrine. "Rôle de la variabilité de Melampsora larici-populina, agent de la rouille des peupliers, et de la structure de la population hôte sur l'évolution des populations de l'agent pathogène." Nancy 1, 1999. http://www.theses.fr/1999NAN10288.
Poplar rust due to Melampsora larici-populina, causes premature defoliation and storage disturbances of cultivated poplars, reducing log production. Poplar cultivars were selected for numerous criteria particularly complete resistance to M. Larici-populina. During the past 20 years, plantation of poplar cultivars expressing different specific resistances regularly resulted in the apparition of new rust races. In 1994, a new group of races, called E4, was detected. These races are now responsible for important damages in young poplar plantations. The number of E4 races increased between 1994 and 1999. Studies on aggressiveness and competitivity of these races demonstrated an important inter and intra-race variability for these biological factors. An increased aggressiveness was observed for recent isolates, compared with early isolates, collected from an abundantly cultivated clone. Furthermore, aggressiveness and competitivity seemed not to be affected by virulence number. Cross-protection, by avirulent races, resulting in a lower infection by a virulent race, was described for the first time on poplar foliar discs. We studied the effects of poplar clone mixtures on rust infection and on plant growth, in comparison with monoclonal plots. The mixture only induced a weak infection reduction, compared with monoclonal plots, and this reduction varied with clone, year, site and racial composition of the pathogen's population. Since the populations of M. Larici-populina are increasingly complex, the interest of poplar clone mixtures in order to control rust epidemics has still to be demonstrated. Furthermore, poplar clone mixtures may induce additional constraints for the poplar growers and the peeling industry
Michard, Céline. "La protéine kinase LegK2 de Legionella pneumophila et le complexe ARP2/3 de la cellule hôte : un nouveau paradigme dans le détournement du cytosquelette d'actine par un pathogène." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10181.
Legionella pneumophila is an opportunistic bacterium that emerges from the environment after multiplication in protozoans and can accidentally infect human alveolar macrophages leading to a severe pneumonia, the legionellosis. The L. pneumophila ability to survive within host-cells is strictly dependent on the Dot/Icm Type 4 Secretion System that translocates a large repertoire of effectors into the host cell cytosol. Deciphering the individual contribution of each bacterial protein translocated by the Dot/Icm system in the L. pneumophila infectious cycle remains a major challenge to understand the molecular basis of Legionella virulence. My works contribute to this objective by characterizing the cellular pathway targeted by the protein kinase LegK2. Interaction and phosphorylation assays identified the actin nucleator ARP2/3 complex as the target of LegK2. Following the LegK2 addressing to the vacuole surface after its translocation into host cytosol, LegK2- ARP2/3 interplay inhibits the actin polymerization on the phagosome. This inhibition allows Legionella to decrease the late endosome/lysosome trafficking towards the phagosome and promotes the phagosome evasion from endocytic degradation pathway. LegK2-ARP2/3 interplay highlights an original mechanism of virulence wherein the local actin cytoskeleton remodeling of host cell allows bacteria to hijack the vesicles trafficking in order to escape host-cell defenses
Abnave, Prasad. "Exploring mammalian immunity against intracellular bacteria through planarian flatworms." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM5049.
Host-pathogen interaction is a vast and complex interplay between pathogen and hostto conquer the battle of pathogenesis. Several model organisms are being studied to illustratethe mechanisms involved in these interactions. In my thesis I have used planarians as a modelorganism to explore host-pathogen interactions. As different model organismscan highlight different features of immunity I decided to take advantage of lack of knowledgeabout planarian immunity and get benefits from exploring unexplored. In my project I haveinfected planarians with 16 pathogenic bacteria and I found that in contrary to othercommonly used model organisms such as Drosophila, C. elegans and zebrafish the planariansare highly resistant to bacterial infections. To explore the mechanism behind this resistance Iperformed infection induced transcriptome profiling followed by RNA interference screeningof up-regulated gens. I discovered genes governing antibacterial resistance in planarians andinterestingly the screening highlighted a gene MORN2 of which the immunological functionwas completely unknown. The human ortholog of MORN2 is then further assessed for itsantimicrobial function. Induced expression and down regulation of MORN2 in macrophagesrevealed that MORN2 controls uptake, replication and trafficking of bacteria inside the cell.In my study I demonstrated that MORN2 is a component of LC3-associated phagocytosis andit can overcome phagosome maturation blockage imposed by pathogenic bacteria. Thus mythesis propounds the importance of using unusual model organisms to unveil unexploredmechanisms and molecules involved in host-pathogen interactions
Möst, Thomas. "Salmonella virulence factors and their role in intracellular parasitism." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4046/document.
Salmonella is an intracellular pathogen, whose virulence relies on the function of two type three secretion systems (T3SSs). The T3SSs are responsible for the delivery of effector proteins into the host cell cytoplasm in order to mediate invasion of the cell and to shape Salmonella's intracellular life.Salmonella's intracellular survival and replication depends on its niche, the Salmonella containing vacuole (SCV), a compartment that is derived from host plasma membrane. Several effectors shape the SCV and give rise to a tubular network, which is implicated in the SCV's stabilization and consists of three different kinds of tubules. We were able to show that the effector proteins SseF and SseG play in concert to form one kind of tubules, the recently discovered LAMP-1-negative tubules (LNTs). Their function is important to Salmonella, as strains having only LNTs but none of the other tubules are able to create a stable SCV, which leads to better replication and virulence in vivo compared to a strain that lacks in tubule formation. Starting from these LNTs as working model, we tried to understand the contribution of tubules to the formation of the SCV and their interactions with the late endosomal / lysosomal compartment (LE/lys). We deciphered the small GTPase Arl8B to play an essential role in the fusion of tubules with LE/lys. Thereby, the knockdown of Arl8B reduced Salmonella's capability to replicate within host cells. We were able to show that an interaction between the effector SifA and Arl8B was responsible for our observations
Manga, Bella. "Etude de la diversité de "Colletotrichum kahawae" responsable de l'anthracnose des baies et caractérisation de la résistance du caféier Arabica à cet agent pathogène." Montpellier 2, 1999. http://www.theses.fr/1999MON20088.
Rouxel, Mélanie. "Ecologie et évolution de l’interaction Plasmopara viticola / Vitis spp. et évaluation des risques de contournement de la résistance de la vigne au mildiou." Thesis, Bordeaux 2, 2012. http://www.theses.fr/2012BOR22023/document.
Understanding the process of adaptation of parasite populations to their host-plant is a key issue in evolutionary ecology. It is also a major subject in applied research that has implications for crop protection. The oomycete Plasmopara viticola, the causal agent of downy mildew, attacks the species of the Vitis genus. In a context where the main concern of the breeding programs is the durability of resistance, new knowledge about the ecology and evolution of the interaction between parasite and host is needed in order to evaluate the potential of downy mildew to overcome the resistance. In my thesis, I addressed the role of the host-plant as an evolutionary factor for downy mildew populations, by asking this question at two different evolutionary scales: (i) in the pathogen region of origin (North America) I assessed the degree of specialization of the parasite on its wild and cultivated host range (ii) in Europe, where downy mildew has been introduced recently, I studied the evolution of downy mildew populations subject to the selection pressure imposed by resistant grapevine varieties. To understand the host-plant specialization in this pathosystem, where several cryptic species have been identified, we performed cross inoculations between different host (Vitis spp.) and pathogen (P. viticola) species. Morphological and phenotypic data provide evidence of host-plant specialization in P. viticola populations: downy mildew species A and D are specialized on their host-plant, while the specialization process is ongoing for species B and C. Although no genetic differentiation has been shown inside species C, there are two distinct groups within species B. Isolates from the cultivated compartment are on average more aggressive than isolates from wild vines, indicating an adaptation of isolates growing on cultivated host-plants. Finally, a large-scale study of the distribution of downy mildew species on both their wild and cultivated host-plants resulted in the identification of a new cryptic species and confirmed the host-plant specialization. In Europe, our results show that the limited deployment of resistant varieties has led to changes in downy mildew populations: emergence of virulent isolates (i.e. breakdown of a major QTL for resistance), and increased aggressiveness on Vitis vinifera. In order to understand the mechanisms at the origin of specialization and resistance breakdown, we examined the parasite’s effector repertoire. Over one hundred effector candidates were identified using available data on the P. viticola genome. The polymorphism of 32 candidate genes revealed that three of them evolve under positive selection. Our results reveal the strong ability of downy mildew to adapt to its host plant and to plant resistance. They should be taken into account when devising strategies for the deployment of grapevine resistances in order to guarantee their durability
Bonnefois, Tiffany. "Expression de marqueurs fluorescents et d'antigènes viraux chez les mycoplasmes, étude d’interactions avec les cellules de l’hôte." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT028/document.
A mini-transposon affording unmarked, stable mutagenesis in mycoplasmas was modified to allow gene expression. This tool was first used for the development of fluorescence expression for stable and innocuous whole mycoplasma cell labelling. For this purpose, the fluorescent proteins GFP2, mCherry, mKO2 and mNeonGreen were introduced as chromosomal tags in the phylogenetically distant species Mycoplasma mycoides subsp. mycoides (Mmm) and Mycoplasma bovis (M. bovis), resulting in the unprecedented observation of red and green fluorescent mycoplasma colonies in the two species, with no apparent cytotoxicity. Equivalent fluorescence expression levels were quantified by flow cytometry in both species, suggesting that these tools can be broadly applied in mycoplasmas. These fluorescent mycoplasmas were then used to compare the adhesion, invasion and persistence of the two species in different bovine cells. They notably confirmed that M. bovis shows a higher adhesion and proliferation capacity to the inert culture surface and higher adhesion to embryonic lung epithelial cells, which it invades. It also shows an increased resistance to elimination by macrophages. However, fluorescent Mmm were also detected inside the phagocytes 72h post-infection, even at a low MOI. Finally, the expression vector was used to assess the possible use of mycoplasmas as vaccine vectors. For this purpose, we introduced the H gene of the “peste des petits ruminants” virus, already used in effective recombinant vaccines, in a caprine mycoplasma as proof-of-concept of a mycoplasma-based multivalent vaccine. However, despite the detection of specific mRNA, the expression of the viral protein could not be evidenced using a highly a sensitive peptide detection technique by mass spectrometry, so this prove of concept could not be delivered. Still, the fluorescence expression tools developed in this study are suitable for host-pathogen interaction studies and offer innumerable perspectives for the functional analysis of mycoplasmas both in vitro and in vivo
Goret, Julien. "Etude de l’interaction de Mycoplasma hominis PG21 avec les cellules dendritiques humaines. : Caractérisation de la fraction bioactive du mycoplasme et réponse immunitaire innée de la cellule." Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0386/document.
Mycoplasma hominis is involved in urogenital tract infections, neonatal infections or disseminated infections particularly in immunocompromised patients. Mycoplasmas have no cell wall and their membrane is the main interface mediating the interaction between the mycoplasma and its environment. Lipoproteins that are anchored to the extracellular side of the plasma membrane are known to induce the maturation of human dendritic cells (hDCs), to stimulate the pro-inflammatory cytokine production by hDCs and to polarize the adaptive immune system. We studied the interaction of M. hominis PG21 with hDCs in order to assess the lipoproteins that can induce the stimulation of hDCs, to determine the lipoproteins that are regulated upon interaction of the mycoplasma with the host cell and to evaluate the innate host cell response. Using a double extraction strategy with two non-denaturing detergents, Sarkosyl then Triton X-114, and separation by SDS-PAGE, we found that 20 lipoproteins may induce the secretion of IL-23 by the hDCs, especially the MHO_4720 lipoprotein. We showed that a synthetic lipopeptide corresponding to the N-terminus part of the MHO_4720 lipoprotein can stimulate the hDCs in a dose-dependent manner. Using qRT-PCR for the evaluation of the transcriptional regulation of the 48 lipoprotein-coding genes of M. hominis PG21, we also determined that 21 lipoproteins were upregulated upon 4h and 24h of contact of M. hominis with hDCs. Finally, the hDC innate immune response was evaluated by PCR array and ELISA. We observed a caspase 5-dependent production of IL- 1β corresponding to the activation of an inflammasome
De, Decker Sophie. "Approches multifactorielles pour l’étude d’interactions entre l’huître creuse Crassostrea gigas et deux Vibrio pathogènes, V. splendidus et V. aestuarianus : épidémiologie, variabilité de la sensibilité de l’hôte et pathogenèse." Thesis, La Rochelle, 2010. http://www.theses.fr/2010LAROS304/document.
Oyster production is the main aquaculture activity in France and is dominated by the rearing of Crassostrea gigas. In the aquatic ecosystems where the species is grown, bacteria of the genus Vibrio are found to be dominant. Two Vibrio species, V. splendidus and V. aestuarianus, are frequently associated with Crassostrea gigas summer mortality episodes. The aims of this work were to study Vibrio-oyster interactions and their modulations according to virulence mechanisms and to genetic and physiological parameters of the host. Using specific, sensitive and quantifying diagnostic tools developed in this study, as well as standardized experimental infection trials, some components of the virulence of Vibrio strains and host susceptibility were delineated and the dynamics of Vibrio infection characterized through pathogenesis studies.The study of the specific diversity of bacterial strains isolated during summer mortality events, on broad temporal and spatial scales, revealed an epidemiological association of the group V. splendidus and the species V. aestuarianus. Because a correlation has been observed between pathogenicity and metalloprotease activity, a predictive phenotypic test of virulence was developed. Exploration of the synergy phenomenon between the pathogenicity of the two strains observed in experimental co-injection led to the characterisation of a system of quorum sensing controlling the production and transcriptional expression of the gene encoding metalloprotease Vsm and Vam at the intraspecific (V. splendidus) and interspecific level (V. splendidus/V. aestuarianus).The statistical analysis of mortality kinetics in half-sib diploid and triploid families subjected to experimental vibriosis by co-infection revealed an increased susceptibility of oysters during the period of active gametogenesis. The triploid oysters subjected to this same experimental infection did not show any significant advantage. The existence of a genetic basis for oyster susceptibility to experimental vibriosis was illustrated by the evaluation of the susceptibilities of fourteen families of the fifth generation (G5) from a program of divergent selection carried out within the MOREST oyster summer mortality research project. This study also allowed the description of co-infections involving the herpes OsHV-1 virus and V. aestuarianus, suggesting multi-etiologic summer mortalities. A pathogenesis study on V. splendidus and V. aestuarianus, performed by cohabitation, was used to explore interactions between C. gigas and pathogenic Vibrio (V. splendidus and V. aestuarianus), or non pathogenic Vibrio found naturally in the endogenous flora of the oyster hemolymph or in the water of the aquaria. This new approach demonstrated a fast transmission of pathogenic Vibrio between infected oysters and sentinels, in less than two hours. Moreover, a significant early and transient disturbance of the defence response of the host was revealed at the transcriptional level during the first six hours of cohabitation. The differential loads of pathogenic and commensal Vibrio in oysters suggest the existence of discriminatory mechanisms, leading to a specificity of the response aiming to eliminate pathogenic Vibrio and maintain a potentially beneficial endogenous bacterial flora in C. gigas
Cossé, Mathilde. "Identification et caractérisation d'un nouvel effecteur précoce de Chlamydia trachomatis." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066083/document.
C. trachomatis is an obligate intracellular Gram-negative bacteria and a human pathogen. It is the most prevalent cause of sexually transmitted diseases of bacterial origin and a leading cause of preventable blindness in the developing world. During their biphasic developmental cycle the bacteria remains in a membrane-bounded cellular compartment called an inclusion. Using a type 3 secretion system (T3SS) they translocate effector proteins inside the cytosol of the cell to promote its survival and multiplication.The aim of the PhD was to study the function of CT622, a hypothetic protein from C. trachomatis. We showed that CT622 is an effector protein from the T3SS and that it is secreted early during the infection. We identified a bacterial protein that binds to CT622, and we showed that it acts as a chaperone, stabilizing CT622 and enhancing its secretion. We obtained bacteria lacking CT622 expression, thus demonstrating that CT622 is not essential for bacterial growth in vitro. However, preliminary studies indicate that in the absence of CT622 bacterial development is delayed and T3SS is defective.We identified several molecules interacting with CT622: geranylgeranyl diphosphate, Rab39 and Atg16L1 proteins. Future work will aim at understanding how these identified interactions, or other bacterial or cellular partners still to be discovered, contribute to the establishment of a niche favorable to bacterial development
Huot, Camille. "Caractérisation et rôle dans l'interaction tripartite du microbiote d'hôtes intermédiaires Planorbidae des parasites trématodes Schistosoma spp. agent responsable de la bilharziose." Thesis, Perpignan, 2019. https://theses-public.univ-perp.fr/2019PERP0041.pdf.
Every living organism is faced, eventually, to microorganisms, whether they are bacteria, viruses, fungi or protists. Microbiota largo sensu represent all these microorganisms, living in a host a T time. It is considered, since years, as an integral compartment of its host. It can affect several host functions, like nutrition, development or immunity. Thus, it can play a key role in interactions between organisms, notably hosts/parasites and hosts/pathogens interactions, improving the immune system of its host or directly affecting the invader. The case of Biomphalaria glabrata and other Planorbidae, intermediate hosts of Schistosoma sp. parasites, responsible agent for bilharzia, is a perfect model to study the role of microbiota in host/parasite interactions. Indeed, understanding the interaction between the worm and its intermediate host could open the way for new measure to fight it, as blocking its lifecycle. The characterization of mollusks' microbiota and its role in the interaction is, thus, an interesting way to explore. During my PhD, I (i) characterized the bacterial and protist microbiota of several Planorbidae species in order to compare it according to host phylogeny; (ii) studied the dynamic of microbiota bacterial communities during an infection kinetic in different B. glabrata strains and; (iii) disturbed the bacterial microbiota and observed the consequences on the mollusks resistance to parasite, in order to highlight a potential role of these bacteria in their host immunity. One of the main results of this work is the high specificity of bacterial communities to their host phylogeny, displaying a phylosymbiosis pattern. Moreover, a variation in infection intensity or prevalence has been highlighted, depending on host/parasite combination, after a microbiota disturbance, suggesting a link between the latter and the antiparasitic immunity of mollusks. Thus, this PhD work is a first step in the understanding of the tripartite interaction between a parasite, its intermediate host and the microbiota of the latter, that could, in time, open new perspectives in the fight against the responsible agent of bilharzia
Perdu, Caroline. "Etude de deux protéines impliquées dans l'injection de toxines par la bactérie Pseudomonas aeruginosa." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENV018.
Pseudomonas aeruginosa, a Gram negative bacterium responsible for nosocomial infections, exhibits numerous virulence factors to infect its hosts. In particular, the Type III Secretion System (T3SS) allows the injection of effectors directly into the host cell cytoplasm. This work focuses on the study of two proteins from the T3SS of P. aeruginosa: the ATPase PscN and the ExsB protein. Several approaches were used to study the ATPase PscN, an enzyme essential for T3SS activity. Site-directed mutations, made on PscN, lead to non cytotoxic strains, and this effect is dominant negative. Another approach allowed the partial purification of active PscN, visualized as large complexes by electron microscopy. These partially purified samples also contain other T3SS proteins, which could interact with PscN. The ExsB protein was characterized for the first time. After checking its expression in P. aeruginosa, its association with the outer membrane was shown. The phenotypic analysis of a strain lacking exsB gene gave insights into the role of this protein. We did not identified any function of ExsB in the T3SS regulation. After showing the involvement of ExsB in the bacterial virulence during acute animal infections, ExsB role in T3SS activity was established. Finally, we showed that ExsB has a pilotin activity as it participates in the assembly of the secretin, the outer membrane component of T3SS
Ferhat, Mourad. "Rôle des pompes à efflux de legionella pneumophila dans la résistance aux biocides et à l’hôte." Thesis, Lyon 1, 2010. http://www.theses.fr/2010LYO10067/document.
Bacterial multi-drug resistance is of major concern in the case of clinic. One of the resistance mecanisms used by bacteria is the efflux of noxious compounds out of the cell thanks to inner membran proteins called efflux pumps. This proteins belong to five families (MFS, RND, MATE, SMR and ABC) and can function in close association with two partners (periplasmic protein and outer membrane protein) to form a canal. In our new research axis based on the study of the drug resistance of the bacterium Legionella pneumophila, we conducted a bioinformatical approach to identify efflux pumps proteins coded by the sequenced genome of three strains (strains Lens, Paris and Philadelphia). Our goal was to study the role of this proteins in Legionella drug resistance and in its virulence. The bioinformatic approach data allowed us to choose one or several genes coding for potential efflux pump components for genetic invalidation by an homologousrecombination strategy. The bacterial mutants were exposed to different noxious compounds in order to know ifthe target genes invalidated were implicated in the efflux of drugs. One of this mutants, strain MF201, which isdeleted for the gene encoding a protein homologous to E. coli TolC protein, revealed to be 2 to 16 times moresensitive to the drug tested compared to the wild-type strain. Furthermore, this mutant showed an importantvirulence defect in Acanthamoeba castellanii, Dictyostelium discoideum and U937 macrophages. This first resultsmeans that the TolC-like protein of Legionella could be a key factor in host-pathogen interaction and stronglysuggests a link between multi-drug resistance and virulence. We also initiated a transcriptomic approach to studyefflux pump genes expression in order to understand their role during the infectious cycle of Legionella
Zhang, Gaotian. "Microsporidia infections in Caenorhabditis elegans and related nematodes." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEE014/document.
Microsporidia are fungi-related intracellular pathogens that infect a great variety of animals, including the nematode Caenorhabditis elegans. The first microsporidia isolated from wild C. elegans was named Nematocida parisii in 2008. C. elegans and N. parisii have been used as a powerful model for the study of host-pathogen interactions. However, it was unclear how widespread and diverse microsporidia infections are in C. elegans or other related nematodes in the wild.By sampling rhabditid nematodes worldwide, we established a collection of 47 nematodes that displayed putative microsporidia infections. We characterized molecularly these infections and determined that N. parisii (or N. ironsii) is the most common microsporidia infecting C. elegans in the wild. We further described and named six new Nematocida species. In addition, we defined two new genera of nematode-infecting microsporidia, named Enteropsectra and Pancytospora, which are genetically distinct from Nematocida. Further investigations showed that these microsporidia are diverse in terms of spore size and shape, host tissue tropism, host cell intracellular localization, cellular exit route, host specificity pattern, etc. Overall, these findings illustrate the widespread and diverse microsporidia infections in C. elegans and related nematodes in the wild.We further assayed the natural variation of C. elegans in sensitivity to N. ausubeli infection, by comparing 10 C. elegans strains using food consumption tests. Two C. elegans strains, JU1249 and JU2825, displayed the largest sensitivity differences, which were suggested to be a result of the different tolerance between the two strains. These two strains are proven to be good candidates for future studies on the genetic loci associated with C. elegans sensitivity variation to microsporidian infections. Furthermore, I observed an exciting effect of host-pathogen interaction. Microsporidia infection is able to suppress the progressive decline in fertility in some C. elegans with the mortal germline phenotype (Mrt)
Carvunis, Anne-Ruxandra. "Des protéines et de leurs interactions aux principes évolutifs des systèmes biologiques." Thesis, Grenoble, 2011. http://www.theses.fr/2011GRENS001/document.
Darwin exposed to the world that living species continuously evolve. Yet the molecular mechanisms of evolution remain under intense research. Systems biology proposes that dynamic molecular networks underlie relationships between genotype, environment and phenotype, but the organization of these networks is mysterious. Combining established concepts from evolutionary and systems biology with protein interaction mapping and the study of genome annotation methodologies, I have developed new bioinformatics approaches that partially unveiled the composition and organization of cellular systems for three eukaryotic organisms: the baker’s yeast, the nematode Caenorhabditis elegans and the plant Arabidopsis thaliana. My analyses led to insights into the evolution of biological systems. First, I propose that the translation of peptides from intergenic regions could lead to de novo birth of new protein-coding genes. Second, I show that the evolution of proteins originating from gene duplications and of their physical interaction repertoires are tightly interrelated. Lastly, I uncover signatures of the ancestral host-pathogen co-evolution in the topology of a host protein interaction network. My PhD work supports the thesis that molecular systems also evolve in a Darwinian fashion
Schmitt, Paulina. "Diversité moléculaire des effecteurs antimicrobiens chez l'huître creuse Crassostrea gigas : mise en évidence et rôle dans la réponse antimicrobienne." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20158/document.
This work contributed to the knowledge of the molecular bases of oyster immunity by the characterization of the diversity of three antimicrobials of C. gigas and the understanding of the role played by their diversity in the oyster antimicrobial response. Phylogenetic analyses of two antimicrobial peptides (AMPs), Cg-Defensins (Cg-Defs) and Cg-Proline rich peptide (Cg-Prp), and one Bactericidal Permeability Increasing protein, Cg-BPI, led us to the identification of a high diversity for both AMPs. Further analyses showed that this diversity is generated by gene duplication, allelic recombination and directional selection pressures, suggesting their functional diversification. The biological meaning of AMP diversity was investigated for the three major variants of Cg-Defs, which revealed a strong but variable potency against Gram-positive bacteria. We evidenced that oyster defensins kill S. aureus through binding to the cell wall precursor lipid II, resulting in the inhibition of peptidoglycan biosynthesis. Finally, transcript expression and localization of oyster antimicrobials after a pathogenic infection evidenced a complex network in their expression profiles in hemocyte populations and oyster tissues, suggesting a potential interplay between antimicrobials as a result of their colocalization. Indeed, the combination of oyster antimicrobials produced strong synergistic activities that enlarged their antimicrobial spectra. Thus, the diversity of oyster antimicrobials may provide significant means in acquiring functional divergence, probably concerned in the evolutionary arms race between hosts and their pathogens.From our data, it would provide oysters with a higher protection against the potential pathogens from their environment
Vignassa, Manon. "Tache noire de l'ananas : déterminisme du processus infectieux par approches moléculaire et biochimique." Thesis, La Réunion, 2021. http://www.theses.fr/2021LARE0013.
In Reunion Island, pineapple crops are exposed to high parasitic pressure promoted by the subtropical climate of the island. The Fruitlet Core Rot (FCR) disease is caused by a set of fungal pathogenic species in which Fusarium ananatum has been the most described so far. The development of brown discoloration in mature fruits represents a major issue affecting notably the quality of the ‘Queen Victoria’ pineapple cultivar due to its high susceptibility to FCR. Until now, the management of epidemics lies on the combination of suitable agricultural practices and the use of fungicide treatments. Nevertheless, these strategies are unsuccessful in the presence of climatic conditions that favor the development and dispersion of causalagents. Mycotoxins accumulation in the flesh of infected fruits is also of concern in the preservation of sanitary quality of fruit productions. In order to develop novel alternatives for sustainable sources of FCR resistance, my research work focused on the determinants of ‘Queen Victoria’ pineapple susceptibility. An epidemiological approach permitted to establish that Fruitlet Core Rot occurrence ispositively correlated to contamination patterns resulting from aerial dispersion of the pathogen spores. Moreover, the prevalence of fungal species belonging to the complexes Fusarium fujikuroi and Talaromyces purpureogenus within the fruit mycobiome have demonstrated the role of a pathogenic fungal set composed of Fusarium proliferatum, Fusarium ananatum, Fusarium oxysporum, Fusarium sacchari, Talaromyces stollii and Talaromyces amestolkiae in the disease expression. The in vitro study of interaction profiles between four of those species have evidenced the growth antagonism of T. stollii on the pathogenic Fusarium species. Significant variations of mycotoxin contents (fumonisins B1, B2 and beauvericin) were also measured during dual culture of pathogens. Finally, the analysis based on varietal comparison of the molecular signal promoting early defense responses show that susceptibility of ‘Queen Victoria’ cultivar is partly supported by a low constitutive expression of genes involved in the synthesis of PR proteins. The results suggest a fungal strategy based on the repression of defense signal transduction in pineapple during the first 72 hours of the host - pathogen interaction leading to the disease establishment
Rahmani, Alexandra. "Identification des facteurs de pathogénicité de la bactérie Vibrio tapetis, responsable de la maladie de l'anneau brun chez la palourde japonaise Ruditapes philippinarum et de mortalités chez les poissons marins Transcriptomic analysis of clam extrapallial fluids reveals immunity and cytoskeleton alterations in the first week of Brown Ring Disease development, in Fish & Shellfish Immunology 93, October 2019." Thesis, Brest, 2019. http://www.theses.fr/2019BRES0059.
The main objective of this thesis is to study the mechanisms related to the pathogenicity of V. tapetis. For this purpose, we developed 2 research axes. The first one aimed at studying the virulence of V. tapetis by answering the following 2 issues: What are the genes involved in the virulence of V. tapetis? and Are there host-specific markers of the virulence of V. tapetis? The second research axis concerned pathogen-host interactions and addressed the following 2 issues: What are the genes expressed during infection in the host? and What are the modulations in the animal associated with pH and temperature during infection? The main findings of this thesis are: (i) V. tapetis, in the context of BRD, induces a down expression of genes involved in the immune response anda deregulation of genes involved in the stabilization and synthesis of actin filaments (ii) This pathogen also induces a decrease in lysosomal activity on exposed hemocytes (iii) The effect of V. tapetis on the actin cytoskeleton and on the decrease in lysosomal activity is independent of the type IV secretion system (T4SS) (iv) The type IV secretion system (T4SS) is involved in the development of BRD but is not essential to induce this disease (v) In the context of BRD and of the loss of hemocyte adhesions properties in vitro, V. tapetis is able to modulate the pH of extrapallial fluids, respectively in the first days and hours of infection (vi) Finally, the "strains typing" approach based on MALDITOF makes it possible to discriminate between V. tapetis strains according to their pathogenicity with regard to Manila clam
Chiron, Hélène. "Effets de l'ozone et/ou d'un champignon pathogène dans les aiguilles et le phloème de pins sylvestre (Pinus sylvestris L. ) : étude moléculaire du métabolisme des stilbènes." Nancy 1, 2000. http://www.theses.fr/2000NAN10047.
The present study describes first the molecular cloning and the functional expression of the pinosylvin O-methyltransferase (PMT) gene, and then the dose-dependent ozone induction of stilbene synthase (STS) and PMT genes responsible of stilbene biosynthesis in needles and sapwood of 7-year-old Scots pine trees prior to sterile and fungal inoculations (Leptographium wingfieldii)
El, Kirat Sofiane. "Développement d’outils cellulaires et moléculaires pour l’étude des interactions Candida - phagocytes ; Application à la caractérisation du gène OLE2 codant une désaturase chez C. lusitaniae." Thesis, Bordeaux 2, 2010. http://www.theses.fr/2010BOR21774/document.
Candida species are opportunistic pathogens causing severe infectious diseases in immunocompromised patients. In this work, we developed a tool for a multi-parameter characterization of the cell interactions between the yeasts Candida and both macrophages and neutrophils, which constitute the main defense against candidiasis. It relies on the labelling of each population with specific fluorescent markers, and on the use of fluorimetry and flow cytometry to assess interactions. The tool has been validated by comparing the interactions of three yeast species C. albicans, C. glabrata and C. lusitaniae, with murine macrophages and human neutrophils. We found that yeasts use two main ways for escaping phagocytosis, which has been confirmed using video-microscopy: either (1) by surviving to phagolysis and dividing into the phagosome until phagocytes burst, or (2) by avoiding phagocytosis and dividing outside phagocytes. In order to better understand the cellular and molecular mechanisms involved in Candida-phagocytes interactions, we developed new molecular tools for the functional analysis of genes in C. lusitaniae, notably a two-step cloning-free PCR-based method for the deletion of genes. This method was successfully used for the deletion of OLE2, a gene encoding a Δ9-desaturase of fatty acids, possibly implicated in prostaglandin PGE2 biosynthesis. The ole2Δ mutant exhibited strong defects in both pseudofilamention and sexual mating. During macrophages infection, ole2Δ yeast cells were massively internalized and triggered less phagocytes cell death than the wild type strain, suggesting that unsaturated fatty acids and/or oxylipids could play a role during interaction with phagocytes. Lastly, a bank of 10,000 mutants was constructed in C. lusitaniae by the random integration of a genetic marker in the genome. The screening of this bank through our tool to analyse cellular interactions will be undertaken to gain insights into understanding of the early stages of the infectious process
Laurent, Benoit. "Base génétique et potentiel d’évolution de la pathogénicité de Fusarium graminearum, bio-agresseur fongique des céréales." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0317/document.
F. graminearum is one of the main causal agents of the fusarium head-blight (FHB), a cereal disease leading to head necrosis, in addition to grain and food/feed contamination by stable and toxic metabolites. Recent observations refer to an increase of pathogenicity, questioning efficiency and durability of current management practices. In order to anticipate this evolution, we must bring a deeper characterization of the currently existing diversity. Six new genomes of F. graminearum were sequenced, and 243,000 genetic variations have been identified and characterized. Seventy seven percent of the total number of the variants was located within 32% of the genome, delineating highly polymorphic islands. These islands are enriched with probable effectors linked to Fusarium’s pathogenicity. The construction and the genotyping on 1,300 molecular markers of a recombinant population have enabled the development of the first high-density genetic map of the species. The remarkable correlation between polymorphism and recombination rate highlighted the 'two-speed' genome organization of this pathogen. Finally, the integration of these data through a quantitative genetic approach allowed the discovery of one quantitative trait locus, likely to affect the gene FgVeA, and responsible for 90% of the observed variation of aggressiveness and mycotoxin production. These results are discussed in the light of F. graminearum’s adaptive potential and evolution
Tamarelle, Jeanne. "Composition et dynamique du microbiote vaginal : facteurs associés et rôle dans l’infection par Chlamydia trachomatis The vaginal microbiota and its association with human papillomavirus, Chlamydia trachomatis, Neisseria gonorrhoeae and Mycoplasma genitalium infections: a systematic review and meta-analysis Vaginal microbiota composition and association with prevalent Chlamydia trachomatis infection: a cross- sectional study of young women attending a STI clinic in France Nonoptimal Vaginal Microbiota After Azithromycin Treatment for Chlamydia trachomatis Infection." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLV097.
Chlamydia trachomatis (CT) is a sexually transmitted bacteria responsible for cervicitis, urethritis, and pelvic inflammatory diseases leading to subsequent tubal infertility and ectopic pregnancies. It is the most frequent sexually transmitted infection worldwide, including in France. Epidemiological data indicate that the incidence rate is increasing despite the implementation of control measures, which motivates the revision of current screening strategies. The vaginal microbiota could play a major role in preventing sexually transmitted infections through ecological competition and metabolites, such as lactic acid production. The vaginal microbiota corresponds to a fine-tuned equilibrium likely to be modified by exposures such as sexual practices, hygiene practices, antibiotics but also presence of pathogens. The overall objective of this thesis is to study the association in this triangle composed of external exposures, vaginal microbiota and CT infection, through the study of the vaginal microbiota composition and dynamics. We aimed at answering these questions: are there biomarkers of CT infection in the vaginal microbiota? Are the vaginal microbiota composition and structure modified by CT infection and antibiotic consumption? What are the exposures associated with perturbations of the vaginal microbiota? To answer these questions, the first step consisted of a state of the art to estimate the association between vaginal microbiota and CT infection in the literature, as well as three other clinically relevant sexually transmitted infections, and to evaluate the role of several factors in the observed heterogeneity between studies. In a second step, we estimated this association using molecular characterization of the vaginal microbiota in two studies in France and in the United States. We showed that Lactobacillus iners-dominated communities (CST III) and Lactobacillus-deprived communities (CST IV) were over-represented among CT-positive women. By studying the vaginal microbiota after azithromycin treatment and CT clearance in the American study, we showed that the vaginal microbiota did not evolve towards an optimal state, suggesting that women may stay at risk of CT reinfections. Finally, in two longitudinal studies using frequent sampling in the United States, we studied exposures associated with incidence and clearance of a CST IV. We showed that when the vaginal microbiota was not dominated by L. iners, menses was the main factor associated with incidence and clearance of a CST IV, while for women whose vaginal microbiota is dominated by L. iners, menses but also lubricant use, douching, ethnic origins, age and condomless vaginal sex were associated with CST IV incidence and/or clearance. Therefore, this thesis allowed on the one hand to confirm the association between Lactobacillus-deprived vaginal microbiota and CT infection using genome sequencing, and on the other hand to single out L. iners from other Lactobacillus spp. and to evaluated the risk associated with CST III. By enabling a better understanding of the natural history of CT and of the vaginal microbiota dynamics, we hope to contribute to improving strategies for the control of CT infection and other STIs. The innovative potential of the project lies in the use of molecular methods, which allows refining of our approach of health management by integrating individual predisposition to sexually transmitted infections, thus paving the way for personalized medicine