Teses / dissertações sobre o tema "Résistance aux antibiotiques – Lutte contre"
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Sevaille, Laurent. "Inhibition de métallo-B-lactamases (MBLs) pour lutter contre la résistance bactérienne aux antibiotiques". Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS136.
Texto completo da fonteThe spread of multiresistant Gram negative bacteria is a growing threat to public health and the risk of return to the pre-antibiotic era is real. Among existing resistance modes, the production of metallo-B-lactamases (MBLs) responsible of the inactivation of B-lactams, the most used family of antibiotics, represents a therapeutical challenge.This manuscript describes the synthesis, characterization and biological evaluation of compounds built on a 2,4-dihydro-3H-1,2,4-triazole-3-thione scaffold substituted on two positions. Based on previous in silico screening and crystallographic studies, which identified this structure as a good candidate for MBLs inhibition, several series have been developed to found new inhibitors that could potentially be amenable to clinical development.First, 1,2,4-triazole-3-thione compounds substituted at position 5 have been prepared following classical pathways. Then, several series have been developed where the structural and functional diversity was introduced at position 4. Compounds have been tested on representative MBLs of the three sub-classes and the most interesting ones on recombinant resistant bacteria.To perform a rapid screening of compounds in the laboratory, a method of medium throughput screening inhibition tests on five MBLs performed in 96-wells plate has also been developed and validated during this study with the help of our collaborators specialists of MBLs
Chevrot, Romain. "Recherche de composés inhibiteurs de la croissance et du quorum sensing de Pseudomonas aeruginosa". La Rochelle, 2007. http://www.theses.fr/2007LAROS215.
Texto completo da fontePseudomonas aeruginosa (Pa) is an ubiquitary, opportunist and pathogenic bacteria, which is more and more resistant to antibiotics. We have researched new molecules from chemical syntheses or bacterial origin, inhibiting the growth or the quorum sensing (QS) of Pa. The synthesized molecules tested have not presented any anti-Pa activity but have allowed the development of protocols used to study the inhibitory activities from bacterial origin. The anti-Pa bacteria have been researched in niches colonized by Pa : poultry intestines, “sanitary” and sputum from cystic fibrosis patients. The study of an anaerobic strain already isolated from duck intestine and presenting an anti-Pa activity has been performed. It belongs to a new species and has been named Megamonas rupella. Its activity is mainly due to the production of propionate and acetate with the possible contribution of a peptidic compound. Two strains related to Paenibacillus alvei inhibiting the growth of Pa and other pathogenic bacteria have been isolated from “sanitary” and pulmonary niches. It is the first time that such an activity is described for this species and that an anti-Pa strain other than a pyocinogenic Pa is isolated from the pulmonary niche. The P. Alvei strains present distinct antimicrobial spectra. In minimum media, one of the P. Alvei produces polymyxin B1 and other antimicrobial peptides. The other strain could produce mainly a fusaricidin like compound. The strains isolated during this work could be used for biocontrol or industrial production of new anti-Pa compounds
Compagne, Nina. "Développement d'inhibiteurs des pompes d'efflux des bactéries Gram négatives pour lutter contre la résistance aux antibiotiques". Electronic Thesis or Diss., Université de Lille (2022-....), 2023. http://www.theses.fr/2023ULILS032.
Texto completo da fonteThe discovery of antibiotics in the 20th century allowed to treat a number of previously fatal bacterial infectious diseases. However, this therapeutic progress was followed by a massive, repeated and inappropriate use of antibiotics, leading to the rise of antimicrobial resistance. This phenomenon is alarming, with an estimated 4.95 million deaths associated with antibiotic resistance in 2019. One of the resistance mechanisms developed by Enterobacterales and overall Gram-negative bacteria is the (over)expression of efflux pumps. These bacterial pumps are able to extrude several classes of antibiotics, thereby reducing their intrabacterial concentration and rendering them ineffective. One strategy being considered to circumvent this phenomenon is the development of efflux pump inhibitors which, in combination with an antibiotic, could offer a new therapeutic alternative to treat resistant bacterial infections.AcrAB-TolC is an efflux pump of the RND superfamily found in Enterobacterales such as Escherichia coli and Klebsiella pneumoniae. In order to identify inhibitors of this pump, a chemical library of 1280 fragments was screened on E. coli in combination with a model antibiotic substrate of this pump, leading to the selection of a hit compound belonging to the pyridylpiperazine family. This hit has no intrinsic antibacterial activity, but is able to potentiate the activity of a range of antibiotics by direct inhibition of the AcrB protein. Initial studies of structure-activity relationships have allowed the identification of two chemical series, the quinoline/quinoxaline series and the pyridine series. Structural modifications around these three cores were carried out using a rational design based on the co-crystallographic structures obtained with AcrB. 80 compounds were therefore synthesised in order to identify more potent analogues and establish new structure-activity relationships. In particular, the introduction of different substituents with an amine function allowed to create new interactions with acidic residues in the AcrB binding pocket. The physicochemical and in vitro pharmacokinetic parameters of the most promising compounds were then measured, leading to the selection of one compound for a pharmacokinetic study in mice. In order to enrich the chemical diversity of substituents introduced on the quinoline and pyridine rings, a chemical library of 672 triazoles was synthesised via a copper-catalysed cycloaddition reaction. The aim was to increase the potency of the compounds by creating new interactions with AcrB while reducing the cytotoxicity and intrinsic antibacterial activity of the compounds. This led to the identification of new compounds with promising activities, which will soon be resynthesised in order to characterise their biological effect and measure their ADME properties
Lôme, Vincent. "Des agents chimiosensibilisants pour lutter contre la résistance aux antibiotiques chez les bactéries Gram-négatif : criblage et caractérisation". Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0063.
Texto completo da fonteGram-negative bacteria are naturally resistant to many classes of antibiotics thanks to their ability to control the accumulation of drugs. Decreasing membrane barrier permeability and producing efflux pumps that expel drugs outside bacteria, represent the prevalent mechanisms of this resistance. One of the most promising solutions consists in restoring antibiotic activity by targeting such barriers to accumulation, with chemosensitizers.The purpose of my PhD was to better understand the inhibition of resistance that opposes the accumulation of antibiotics in Gram-negative bacteria.In the first stage of the study, the activity of various synthetic chemosensitizers has been characterized. Three compounds were identified to significantly increase the synergistic activity with antibiotics, that was previously observed with geraniol. These derivatives showed an efflux pump inhibition or an outer membrane permeabilization effect, that could be related to the observed synergy.In the second stage of the study, a screening method has been developed for the specific detection of chemosensitizers, while describing their mechanism of action.This work participated in proposing a patented therapeutic solution in the preclinical stage. This study has led to new tools to identify novel chemosensitizers, but also to better understand how to impair the barriers opposing the accumulation of antibiotics
Bailleul, Geoffrey. "Les défensines aviaires : nouveau moyen de lutte contre les entérobactéries pathogènes". Thesis, Tours, 2016. http://www.theses.fr/2016TOUR3813.
Texto completo da fonteLarge-scale use of antibiotics has leaded to the emergence of multi drug resistant bacterial strains, particularly in the genus Salmonella and Escherichia coli responsible for infectious diseases outbreaks. This constitutes a major veterinary and public health concern. Host defense peptides (HDPs) represent major effector molecules of the animal’s innate immune system. In birds, the main family of HDPs is composed of avian defensins whose two members (AvBD2 and AvBD7) isolated from chicken bone marrow exhibit large spectrum antibacterial activity. Thus, they both constitute potential candidate molecules as alternative to antibiotics. To demonstrate the therapeutic interest of AvBD2 and AvBD7, we have (1) proved their antibacterial efficiency in vitro towards clinical and multi drug resistant bacterial strains, (2) shown their functional and structural stability when facing major digestive proteases, (3) identified a novel antibacterial effect in infected macrophages, and finally (4) proved the therapeutic concept by reducing mortality and bacterial load after AvBD7 injection in a murine model of lethal salmonellosis
Majdi, Chaimae. "Lutte contre l'antibiorésistance : synthèse de dérivés de tryptamine et de juglone. Evaluation de leurs activités antibactériennes et d’adjuvants d’antibiotiques. Etudes de leur biodégradabilité". Electronic Thesis or Diss., Nîmes, 2024. http://www.theses.fr/2024NIME0003.
Texto completo da fonteGlobal health is threatened by antibiotic resistance at an unprecedented level today. As a result, the World Health Organization (WHO) now identified bacterial resistance as a "silent pandemic". As part of a global plan to combat antibiotic resistance, the WHO warned that infectious diseases will be the leading cause of death worldwide by 2050 unless action is taken now. A total of twelve families of antibiotic-resistant bacteria have been classified as critical, high, and medium priority organisms based on their resistance to antibiotics.This thesis project involved four studies to respond to this urgency. As part of the first one, five inhibitors of bacterial response regulators (RR, a protein involved in the bacterial resistance mechanism) were evaluated for their antibacterial and antibiotic adjuvant activity against bacteria classified as a critical priority by the WHO. It was observed that two of these five compounds demonstrated an excellent cefotaxime adjuvant activity by reducing its minimum inhibitory concentration by 256,000-fold and showing a remarkable synergistic effect against a clinical strain of Escherichia coli resistant to cefotaxime. The second study aims to design and synthesis of 64 tryptamine and naphthol derivatives and investigated them as antibiotic adjuvant agents against bacterial strains, which are also of critical priority. One tryptamine derivative from the carboxamide family showed the best activity, potentiating cefotaxime (267-fold) synergistically against Escherichia coli strain resistant to cefotaxime. The third study aimed to optimize the clinical use of colistin, the only last-resort treatment for life-threatening infections caused by enterobacteria. In this context, nineteen tryptamine derivatives from the urea family were synthesized and investigated as colistin adjuvants against clinical colistin-resistant strains. Among these derivatives, one compound showed particular potential as an adjuvant agent in the presence of colistin, with a 64-fold against the clinical colistin-resistant strain of Klebsiella pneumoniae. Finally, a fourth study involved the regioselective synthesis of sixteen aminojuglone derivatives under eco-friendly conditions using Michael addition in the presence of CeCl3·7H2O, and the evaluation of their biological activity against high-priority Gram-positive bacterial strains. Twelve compounds showed cloxacillin adjuvant effect with 4 to 66-fold on a clinical strain of methicillin-resistant S. aureus (MRSA). Only one of these twelve compounds complied with the "antibiotic adjuvant" concept, devoid from antibacterial activity while synergistically restoring the activity of cloxacillin (66-fold) against MRSA.All synthesized compounds possessing the best biological activity in this research work, are devoid of antibacterial activity while synergistically restoring antibiotic activity against resistant bacterial strains which is in line with the antibiotic adjuvant concept
Ntsogo, Enguene Véronique Yvette. "Nouvelle approche dans la lutte contre la résistance aux antibiotiques des bactéries colonisant les poumons des patients atteints de mucoviscidose : reconstitution d'une pompe d'efflux de Pseudomonas aeruginosa". Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCB146/document.
Texto completo da fonteMultidrug efflux systems are membrane transport proteins that are used to translocate a wide variety of drugs across the inner and the outer membranes of Gram-negative bacteria, leading to natural and acquired antimicrobial resistances.Most of the multidrug transporters of P. aeruginosa belong to the resistance-nodulation-cell division (RND) superfamily.They function as three-component assemblies made of an inner membrane transporter (RND), a periplasmic membrane fusion protein (MFP) and an outer membrane factor channel (OMF). Along with functional studies, many crystal structures of the individual components of the pump have been solved but the interactions underlying the complex assembly and the opening mechanism of the outer channel remain unclear. In this study, we investigated structural and functional insights of P. aeruginosa efflux pumps. We solved the crystal structure of the MexEF-OprN efflux pump outer membrane channel OprN mainly involved in fluoroquinolones resistance. Our new structure highlights the differences between P. aeruginosa and other Gram-negative bacteria OMFs that could explain their specific interaction with the cognate MFP partners. We also purified and characterized the inner membrane transporter MexY from the MexXY-OprM efflux pump, which is the major determinant of aminoglycosides resistance in P. aeruginosa. Besides, we solved the crystal structure of a mutatedform of the outer membrane channel OprM in order to understand its opening mechanism. We also investigated in vivo effect of the OprM mutants in antibiotics resistance by MIC measurements and tried to correlate with the observed structural modifications leading to the open state. Moreover, we set up a new in vitro test allowing the investigation of the assembly of the MexAB-OprM efflux pump. Our results showed the importance of MexA and its lipid anchor in promoting and stabilizing the complex assembly. In addition, as a side project with the group of Pr Plésiat (laboratoire de Bactériologie de Besançon), we built different structural models of AmpC mutants from overproducing clinical isolates,showing the possible conformational changes that lead to the resistance increase
Opatowski, Lulla. "Modélisation mathématique de la dynamique de diffusion de bactéries résistantes aux antibiotiques : application au pneumocoque". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2009. http://tel.archives-ouvertes.fr/tel-00814070.
Texto completo da fonteMadi, Moussa Désiré. "Caractérisation de l’activité contre les bactéries à Gram-négatif, expression hétérologue et étude de la relation structure activité des bactériocines produites par Lacticaseibacillus paracasei CNCM I-5369". Electronic Thesis or Diss., Université de Lille (2018-2021), 2021. http://www.theses.fr/2021LILUR060.
Texto completo da fonteThe excessive use of antibiotics has exacerbated the phenomenon of antibiotic resistance throughout the world. Today, the fight against antibiotic resistance has become a global public health priority. Indeed, every year, it is responsible for more than 700,000 deaths in the world and by 2050, it will cause more than 10 million deaths per year, if concrete actions are not implemented to curb the development of this phenomenon. In addition to the human losses, the financial cost of antibiotic resistance-related care could reach 100,000 billion dollars worldwide. To face this crisis, several innovative strategies, including the use of antimicrobial peptides (AMPs), have been proposed. In this perspective, bacteriocins, which are ribosomally APMs, could contribute to the therapeutic solution. Recently, the Lacticaseibacillus paracasei CNCM I-5369 strain has been particularly distinguished for its activity against Gram-negative pathogens. This activity is due to 5 new bacteriocins encoded by chromosomal genes orf010, orf012, orf023, orf030 and orf038. However, the activity is pH-dependent, i.e., it is exerted, only at a pH value ≤ 5. In the framework of this thesis, we first verified the expression of these genes during the growth of the bacteria, using the qPCR technique. Thus, we observed that these 5 genes were expressed after 24 h of growth, concomitantly with the appearance of antimicrobial activity indicating a possible link between gene expression and the production of the five bacteriocins. These 5 bacteriocins were expressed in a heterologous system in Escherichia coli Rosetta. It should be noted that only the bacteriocin encoded by orf030, called lacticaseicin 30, could be produced in large quantities, in contrast to the other bacteriocins which were produced but remain trapped in the insoluble fraction. In a second step, we investigated the relationship between the structure of lacticaseicin 30 and its activity against Gram-negative bacteria. Structural predictions suggested a 5-helix organization of lacticaseicin 30. The proportion of helix-α was greater at pH 5 than at pH 7. To identify the regions involved in the activity against Gram-negative bacteria, we produced lacticaseicin 30-derived peptides by a molecular biology approach. These derived peptides are obtained by reducing their sizes, or by inserting targeted mutations in different regions. Thus, we generated shorter forms of lacticaseicin 30, containing either its N-terminal region (amino acids 1 to 39), or the central and C-terminal regions (amino acids 40 to 111). Similarly, a derivative peptide containing only the first helix of the N-terminal region was also produced. Mutations introducing amino acid substitutions were introduced within the α-helices. With regard to their activities, these derived peptides localized antibacterial activity mainly in the N-terminal region, and requires at least two helix-αs. Furthermore, the activity of these peptide variants E32G, T33P, T52P, and D57G remained essentially the same, unlike to those of the variants E6G, T7P, D57G T52P, A74P, Y78S, Y93S, and A97P, which were significantly impaired. In the last part, we tested the activity of lacticaseicin 30 against a panel of Gram-negative clinical strains with colistin resistance. The results obtained highlighted a synergy between lacticase 30 and colistin and a significant reduction of the expression of the mcr-1 and mcr-9 genes, responsible for colistin resistance
Nicol, Marion. "Recherche d'outils thérapeutique innovants pour lutter contre la bactérie Acinetobacter baumannii". Thesis, Normandie, 2017. http://www.theses.fr/2017NORMR132/document.
Texto completo da fonteToday, Acinetobacter baumannii is one of the most problematic pathogens in the world. This bacterium is responsible for worldwide epidemic outbreaks associated with dramatic mortality rates. It possesses high capacities to evade the immune host system and to resist to numerous available antibacterial agents. A. baumannii is also able to persist into hospital environment due to high adhesion abilities which induce community development. This process is also associated to an enhanced survival rate. In Acinetobacter genus, community modes of lif can take two forms : biofilm and pellicle. In this study on the strain ATCC 17978, we tried to discriminate these two lifestyles by a large scale proteomic analysis. We have confirmed the presence of many common community markers (transporters, ion acquisition secretion systems, adhesins and pili) and highlighted systems specifically related to biofilm (pilus Fim, T2SS, T1SS / pump A1S_0535-38, LPS / LOS, capsular pattern) and pellicle communities. Furthermore the proteomic analysis of an avirulent A. baumannii strain, SDF, in biofilm allowed to highlight peculiar metabolic pathways, specific adhesion determinants but very few markers shared by ATCC 17978. This demonstrated the difficulty in developing a treatment directed against A. baumannii biofilm. Then, we tested different approaches to prevent and eradicate biofilms. The first one targeted the Quorum Sensing system (QS), an essential communication system for cell coordination. We have showed that monounsaturated fatty acids (palmitoleic acid and myristoleic acid), like virstatin prevent the community formation of A. baumannii by inhibiting the expression of the abaR regulator required for QS. In a second strategy, we have evaluated the antibacterial and antibiofilm activity of a new natural compound : the squalamine. We showed for the first time that if ciprofloxacin treatment was able to induce a dormancy population (persistent/VBNCs) in A. baumannii, squalamine was able to eradicate this population of dormant cells
Moulenat, Rufingier Catherine. "Résistance aux insecticides et structure génétique des populations de "Nasonovia ribisnigri"(Mosley)(Homoptera : aphididae)". Montpellier 2, 1998. http://www.theses.fr/1998MON20049.
Texto completo da fonteLopes, Julie. "Développement de nouvelles stratégies de lutte contre les biofilms de Providencia stuartii, un pathogène humain multi-résistant". Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAV025/document.
Texto completo da fonteBacterial biofilms are multicellular communities adherent to surfaces and surrounded by an extracellular matrix. They are crucial for maintaining most of our planet’s ecosystems, but also a threat to human health. Biofilm eradication is one of the greatest challenges of modern microbiology due to their high resistance to antibiotics. In this PhD, we focused on Providencia stuartii, a Gram-negative pathogen that forms biofilms in the human urinary tract and is responsible for about 10% of hospital-acquired urinary tract infections. P. stuartii exploits an additional means of socialization, forming floating communities of cells (FCCs), that later sediment and adhere onto surfaces yielding surface-attached biofilms (SABs). The two porins of P. stuartii, Omp-Pst1 and Omp-Pst2, are involved in FCC formation by self-association into intercellular dimers of trimers (DOTs). The main driving force behind DOT formation is electrostatic attraction, yet the DOT structure is locked-in by steric zipper interactions between facing extracellular loops.The two main objectives of this PhD were (i) to characterize the environmental impacts on the establishment and survival of the two type of socialized communities formed by P. stuartii, and (ii) to inhibit bacterial socialization by targeting porin DOTs. Our results reveal that peptides featuring residues involved in the steric zipper interaction of DOTs, and coupled with coumarin, are promising lead compound to diagnose P. stuartii infections. In addition, we tested combinations of antibiotics with some of these peptides and results suggest that is was a new therapeutic approach that can be envisaged to fight against P. stuartii infections. Future treatments should be evaluated on FCCs and SABs in conditions mimicking urinary tract, to be efficient and potentially eradicate P. stuartii
Berrada, Sai͏̈d. "Etude de la sensibilité de Psylla pyri L. (Homoptera : Psyllidae) aux produits phytosanitaires et mécanismes biochimiques de résistance aux organophosphorés". Toulouse 3, 1994. http://www.theses.fr/1994TOU30021.
Texto completo da fonteMalembic, Sylvie. "Evaluation de la stratégie planticorps comme méthode de lutte contre les mollicutes phytopathogènes : Action in vitro d'anticorps recombinants sur Spiroplasma citri : Résistance de tabacs exprimant des anticorps recombinants à l'infection par le phytoplasme du stolbur". Bordeaux 2, 2001. http://www.theses.fr/2001BOR28900.
Texto completo da fontePhytoplasmas are phloem-restricted wall-less bacteria of the class mollicutes which have resisted in vitro cultivation so far. They are responsible for numerous plant diseases and there is no curative method for disease control. An antibody-based resistance method is evaluated in our laboratory for the stolbur phytoplasma. It consists in expressing scFv recombinant immunoglobulins (Ig) specific for this phytoplasma in tobacco plants, natural hosts for this pathogen. First we demonstrated that both native Ig and recombinant scFv, specific for the major surface protein of the culturable phytopathogenic mollicute Spiroplasma citri, inhibit its growth in vitro. Secondly, we engineered various anti-stolbur scFv constructions for their expression in tobacco plants via the apoplastic (35-pel-scFv plants) or symplasmic (35-scFv and RSS-scFv-KD) pathway, to evaluate their production into the phloem sap were phytoplasmas are located. Our results indicate that scFv, although produced in large amounts in 35-pel-scFv tobaccos, were probably not, or only slightly, present in the phloem sap. Only a transient disease resistance was observed in these plants. Indeed, it has been recently demonstrated that many phloem sap proteins are produced in the cytoplasm of companion cells and that they move towards sieve tubes via plasmodesmatas. Transgenic tobaccos plants in which scFv expression was targeted to the cytoplasm either constitutively (35-scFv) or specifically to phloem tissues (RSS-scFv-KD), in spite of a good transcription of scFv mRNAs, did not produce detectable amounts of scFv. These tobaccos, as previously, showed little resistance to the disease. As scFv inhibit in vitro growth of phytopathogenic mollicutes, the plantibody strategy appears to be well adapted to control phytoplasma diseases. However, targeting scFv in the phloem sap has to be optimized and various alternatives for sap targeting are discussed
Marcombe, Sébastien. "Résistance de Aedes aegypti aux insecticides à la Martinique et implications dans la lutte contre la dengue". Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20001/document.
Texto completo da fonteThis thesis was conducted in the context of the resurgence and expansion of dengue fever throughout the world, particularly concerning France. Current strategies of control of the virus and its vector Ae. aegypti encounter many limitations. These involve economic, sociological, legal, environmental and biological dimensions. This study aimed to take into account some of these limitations in the setting of Martinique, which on a micro-geographical level presents all the necessary parameters to study the causes and consequences of the expansion of insecticide resistance on the effectiveness of vector control. Initial work aimed to increase our knowledge of the metabolic and molecular mechanisms implied in resistance. We then evaluated the distribution and mechanisms of resistance occurring in various populations of mosquitoes on a macro-geographical level. This allowed us to study the environmental factors contributing to selection of resistance mechanisms in the field. Finally a population genetic study enabled us to measure genetic variability and the structure of these vector populations. The second part of the study aimed at understanding the impact of resistance on vector control operations. The phenotypic expression of resistance was investigated in the laboratory and field by measuring the survival rates of mosquitoes exposed to various types of insecticide treatment (larvicide/adulticide). In the last part of this thesis we investigated alternative or innovative strategies of vector control with the objective of contributing towards improved management of resistance within vector populations. The evolution and future of research concerning the fight against Ae. aegypti and dengue is discussed in this study
Demay, Fanny. "Mécanismes moléculaires impliqués dans la protection du ribosome contre les antibiotiques". Electronic Thesis or Diss., Université de Rennes (2023-....), 2023. https://ged.univ-rennes1.fr/nuxeo/site/esupversions/c2dfb8a5-d6bc-41e6-858f-912fcbc4864b.
Texto completo da fonteThe work carried out focuses on the characterisation of a resistance mechanism described in E. faecium. A single nucleotide mutation in the eat(A) gene leads to the substitution of an amino acid (T450I) coding for the variant form of the Eat(A)v protein. This mutation leads to cross-resistance to different antibiotics (Lincosamides, Streptogramins A and Pleuromutilins) which all target the peptide transfer centre of the ribosome. Eat(A) is one of the ABC-F proteins, some of which are Ribosome Protection Proteins, while the role of the wild type remains unknown. The aim of this thesis is to characterise the biological activity of the two forms of the Eat(A) protein. The mutation causing the resistance phenotype is located 3 residues upstream of one of the two ATP hydrolysissites. A difference in ATPase activity between the native and the variant form of the protein may be at the origin of the resistance mechanism. To address these questions, we developed a purification method to obtain sufficient soluble protein for in vitro assays. We studied the impact of the T450I mutation on the ATPase activity of the proteins, revealing the importance of isoleucine in the biological activity. We also developed an in vitro translation system using E. faecium S30 extracts to study the impact of the two Eat(A) proteins on translation by monitoring GFP synthesis, with or without antibiotics. Finally, we undertook the characterisation of the interactions between the two forms of Eat(A) and the E. faecium ribosome using cryo-EM technology
Vorac, Jaroslav. "Le fonctionnement du transporteur ABC de Streptococcus pneumoniae impliqué dans la résistance contre les peptides antimicrobiens". Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAV009/document.
Texto completo da fonteStreptococcus pneumoniae, the pneumococcus, is a major human pathogen causing over a million deaths each year. Many pneumococcal strains display resistance towards antibiotics causing world-wide health concern. Some of these antibiotics are antimicrobial peptides (AMP), which are produced as a primary defense by hosts as well as pathogens. The pneumococcus harbors a system comprised of an ATP-binding cassette (ABC) transporter and a two-component system (TCS) composed of a histidine kinase (HK) and a response regulator (RR), which targets these molecules. It has been shown recently that the removal of this ABC transporter increases the sensitivity of the bacteria towards bacitracin. In this project, we tried to understand the functioning mechanism of the ABC transporter and the co-operation with the TCS using both in vivo and in vitro techniques
Samain, Erika. "Étude des interactions PGPRs/génotypes de blé tendre dans la lutte contre la septoriose". Thesis, Amiens, 2019. http://www.theses.fr/2019AMIE0027.
Texto completo da fonteSeptoria tritici leaf blotch (STB) caused by Mycosphaerella graminicola is regarding as the most important disease in wheat. The present work aims to study the durability and efficiency of the plant-growth-promoting rhizobacteria (PGPR)-induced resistance (IR) against STB. Many of PGPR were screened, in single and co-inoculations, for their root colonization, plant growth promotion (PGP) and IR, using different wheat genotypes. However, two effective PGPR-mixtures were identified, Mix2; Paenibacillus sp. strain B2 (PB2) with an effective approval strain AA and Mix3; PB2 with Microbacterium SSM001 and Arthrobacter SSM004, in equal portions. PGPR in Mix2 and Mix3 showed ecto- and endophytic root colonization until the flag-leaf growth stage (FL), with a helper impact on root colonization by PB2. Only, with Mix2 and 3, PGP was observed. Under drought stress, the IR by Mix2 and 3 was more efficient compared to PB2. However, all of them showed high and durable IR against STB until FL, which seems to be more correlated to PB2 and depends on plant-genotype, growth-stage and M. graminicola strain. Interestingly, the high PGPR-IR against STB was confirmed under field conditions. Using the non-sterile field soil, they didn’t show significant impact on the soil microbial communities (SMC), using the 16S rDNA and ITS MEGA sequencing. But, a significant reduction in the PGPR’ efficiency was recorded, only, for PB2 and Mix3, and in some tested cultivars. Gene expression analysis of the PB2-, Mix2- and Mix3-IR showed upregulations of gene markers involved in the basal defenses, JA, phenylpropanoids & phytoalexins and ROS pathways, with stable priming inductions of Pr1, glucanase, and flavonoide, suggesting them as protection markers. We identified an effective PGPR-mixture induces high and durable and stable resistance against STB and drought stresses, promotes plant growth, and without disturbance on the SMC. The global results may help to reduce gap between laboratory and field results
Amensag, Kamar. "Les bactéries lactiques isolées d'aliments traditionnels marocains : production de bactériocines et applications potentielles contre des pathogènes multirésistants aux antibiotiques". Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAF024.
Texto completo da fonteAntibiotic therapy has been effective in controlling many infectious diseases, but is slowly reaching its limits with the emergence of multidrug-resistant microorganisms. The search for alternative molecules has become a necessity. This thesis explores the possibility of using antibacterial peptides (bacteriocins) produced by bacteria as a means to fight resistant bacteria. Strains of lactic bacteria producing bacteriocins have been isolated essentially from various fermented Moroccan foods. The bacteriocins produced were purified by chromatographic techniques, and their structures were elucidated by mass spectrometry, peptide sequencing and / or nucleotide sequencing. This allowed the identification of one or more bacteriocins per producing bacterium, e.g. enterocins L50A and L50B produced as modified forms by Enterococcus durans LC2 isolated from camel milk. At the same time, the search for multidrug-resistant bacteria in human body fluids has resulted in the isolation of pathogenic bacteria of both Gram types resistant to a variety of commonly used antibiotics. Among these, selected strains were subjected to the action of purified bacteriocins (enterocins L50A and L50B, nisin Z and pediocin PA-1) alone and in combination with antibiotics. This allowed us to show the efficacy of bacteriocins against multi-resistant pathogens, thereby demonstrating their potential as a possible alternative in case of antibiotic inefficiency
Hugot, Karine. "Mécanismes de défense des plantes et acquisition de résistance aux champignons pathogènes : caractérisation d'effecteurs apoplastiques et étude du mode d'action de la RNase NE". Nice, 2000. http://www.theses.fr/2000NICE5480.
Texto completo da fonteCorbel, Vincent. "Interactions entre insecticides sur "Anopheles gambiae" giles et "Culex quinquefasciatus" say et impact sur l'évolution de la résistance". Montpellier 2, 2003. http://www.theses.fr/2003MON20076.
Texto completo da fonteGuillet, Pierre. "La lutte contre les vecteurs de l'onchocercose en Afrique de l'Ouest : étude de la résistance et recherche de nouveaux larvicides". Paris 11, 1985. http://www.theses.fr/1985PA112383.
Texto completo da fonteDelannoy, Etienne. "Caractérisation de péroxydases associées à la défense du cotonnier ("Gossypium hirsutum") contre "Xanthomonas campestris" pathovar "Malvacearum"". Montpellier 2, 2003. http://www.theses.fr/2003MON20175.
Texto completo da fonteRouane, Sébastien, e Sébastien Rouane. "Doses minimales biologiquement efficaces pour le désherbage dans la rotation de maïs-soya tolérants au glyphosate et au glufosinate". Master's thesis, Université Laval, 2009. http://hdl.handle.net/20.500.11794/21326.
Texto completo da fonteUne étude ayant pour objectif d'évaluer différentes séquences d'herbicides en condition de doses réduites, a été mise en place à la station agronomique de l'Université Laval pendant trois ans. Huit séquences culturales de maïs (Zea mays) et de soya (Glycine max) tolérant au glyphosate et au glufosinate ont été testées avec quatre doses d'herbicides. Les résultats montrent que l'emploi du glufosinate trois ou deux années de suite en remplacement d'une utilisation continue du glyphosate paraît difficilement envisageable. Des problèmes de répression et des baisses de rendement sont visibles en présence d'une flore mixte (présence de graminées annuelles en particulier). L'utilisation de doses réduites de glufosinate n'est pas conseillée pour les mêmes raisons. Concernant le glyphosate, une réduction d'un quart de la dose homologuée semble réalisable du point de vue des rendements des cultures, mais présente toutefois un risque d'augmentation de la banque de graines au bout de deux années d'utilisation répétée.
Fonteyne, Pierre-Alain A. "Définition de marqueurs génétiques pour la lutte contre les infections mycobactériennes :identification rapide de l'espèce et détection de la résistance aux fluoroquinolones". Doctoral thesis, Universite Libre de Bruxelles, 1997. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/212240.
Texto completo da fonteGuérin, Fabien. "Mise en évidence d'une population génétiquement différenciée de Venturia inaequalis, agent de la tavelure du Pommier, associée au contournement du gène majeur de résistance Vf". Angers, 2004. http://www.theses.fr/2004ANGE0021.
Texto completo da fonteStrategies of genetic control against the phytopathogenic fungus Venturia inaequalis are mainly based on the use of major resistance genes which confer a complete resistance towards the disease. By the end of the Eighties, strains virulent against Vf, the most used resistance gene were evidenced. This thesis was aimed at understanding the evolutionary dynamics of pathogenic populations confronted to selection pressures exerted by a major gene of resistance. Thanks to the use of molecular markers, such as microsatellites and AFLP, we followed up the genetic structure of V. Inaequalis populations in several locations over several years. Our results showed that the genetic diversity of virVf populations drastically decreased as compared to the avrVf populations, revealing the typical structure of a founder effect. In addition, we showed that virVf populations were strongly differentiated from the avrVf populations and that they were stochastically dispersed over Europe from a common source of virulence. Finally, we revealed the maintenance of the genetic differentiation in space and time between virVf and avrVf populations. The lack of gene flow between virVf and avrVf compartments indicated a reproductive isolation of virVf strains, which could be partly explained by the avirulence spectrum of these strains towards some of the non-Vf hosts in the studied orchards. Results obtained from this work allowed us to discuss on the origin and the dispersion of the Vf virulence and then to propose topics to investigate in order to preserve the efficiency of the Vf resistance gene
Expert, Jean-Michel. "Lutte biologique contre les attaques précoces de Sclerotinia sclerotiorum du tournesol à l'aide de Pseudomonas spp. Fluorescents et de Bacillus spp". Lyon 1, 1995. http://www.theses.fr/1995LYO10221.
Texto completo da fonteStiévenard, Catherine. "Reproduction sexuée d'Uncinula necator (schw. ) Burr. , agent de l'oïd͏ium de la vigne : maîtrise in vitro et rôle dans la résistance aux fongicides inhibiteurs de la biosynthèse des stérols". Bordeaux 2, 1998. http://www.theses.fr/1998BOR20569.
Texto completo da fonteMuvunyi, Robert. "Induction de la résistance des carottes aux maladies post-récoltes par un traitement préentreposage au moyen des rayons ultraviolets (UV-C) : orientation des carottes au cours du traitement et nature de la résistance induite". Thesis, Université Laval, 2012. http://www.theses.ulaval.ca/2012/28934/28934.pdf.
Texto completo da fonteAli-Haimoud, Djamel-Eddine. "Contribution à l'étude de la lutte biologique contre Drechslera teres (Sacc. ) Shoem. , parasite de l'orge". Toulouse, INPT, 1994. http://www.theses.fr/1994INPT007A.
Texto completo da fonteMartin, Thibaud. "La résistance aux insecticides de Heliccoverpa armigera (Hübner) en Afrique de l'Ouest : du mécanisme à la gestions". Toulouse 3, 2003. http://www.theses.fr/2003TOU30087.
Texto completo da fontePennetier, Cédric. "Interactions entre insecticides non-pyréthrinoïdes et répulsifs pour la lutte contre Anopheles gambiae : mécanismes, efficacité et impact sur la sélection de la résistance". Montpellier 1, 2008. http://www.theses.fr/2008MON1T004.
Texto completo da fonteZogo, Mahugnon Barnabas. "Impact entomologique de stratégies complémentaires de lutte intégrée contre le paludisme dans un contexte de résistance des vecteurs aux insecticides au nord de la Côte d’Ivoire". Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTT056.
Texto completo da fonteThe spread of pyrethroid resistance in malaria vectors and the stalling of recent progress in malaria control in Africa highlight the urgent need to deploy complementary strategies to long-lasting insecticidal nets (LLINs) to accelerate the reduction in the disease burden. Strategies such as strengthened Information, Education and Communication (IEC), Indoor Residual Spraying (IRS) and larviciding with Bacillus thuringiensis isralensis (Bti) are available but the actual benefit of their use in combination with LLINs remains to be demonstrated. The main objective of this work was to measure the additional impact of these three strategies on malaria transmission through a randomized controlled trial run in 28 villages in the health district of Korhogo, northern Côte d’Ivoire, an area of vector resistance to pyrethroids. Prior to the deployment of these strategies, my work allowed us to 1) assess the efficacy of a new larvicide formulation under semi-field conditions; 2) study vector bionomics, insecticide resistance mechanisms and malaria transmission; 3) identify and characterize Anopheles spp. breeding habitats in the study area. Data from post-intervention surveys showed 1) a reduction of vector density (69%) five months after the beginning of the IEC strategy, of sporozoïte rate (84%) and of IER (86%) in the LLIN+IEC arm relative to the LLIN alone arm; 2) a reduction of vector density at months two (72%) and four post-IRS (69%) and of EIR (62%) in the LLIN+IRS arm relative to the LLIN alone arm; 3) a reduction of vector density (95%) three months after the beginning of larviciding intervention and of IER (88%) in the LLIN + larviciding arm relative to the LLIN alone arm. These results provide evidence that IEC, IRS and larviciding are effective complementary strategies to reduce transmission intensity in Korhogo. Analysis of epidemiological data collected during the trial will allow a better understanding of the additional benefit of these strategies on the malaria burden
Jouy, Nicolas. "Etude de la résistance naturelle de deux Lycopersicon à des ravageurs de cultures maraîchères : identification des substances responsables, les (2,3,4-tri-O-acyl)-}a-D-glucopyranosyl)-(3-O-acyl)-b-D-fructofuranoside". Montpellier 2, 1990. http://www.theses.fr/1990MON20278.
Texto completo da fonteLegnani, Robert. "Analyse, comparaison et exploitation des résistances au virus Y de la pomme de terre (PVY) et au tobacco etch virus (TEV) chez la tomate". Montpellier 2, 1995. http://www.theses.fr/1995MON20240.
Texto completo da fonteGarnault, Maxime. "Étude de l’évolution des résistances aux fongicides chez Zymoseptoria tritici, agent de la septoriose du blé, et quantification multi-échelle de ses déterminants". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLA030.
Texto completo da fonteSeptoria leaf blotch is a major wheat disease caused by the pathogenic fungus Zymoseptoria tritici. It can induce yield losses up to 50%. The control of this pathogen relies on cultivar resistance, cultural control but mostly on the use of fungicides. However, the sustainability of chemical control is threatened by the emergence of resistant mutants, i.e. individuals with decreased sensitivity to one or several active ingredients. When resistance factors and/or resistance frequencies are high in populations, chemical control efficacy can be jeopardized. Therefore, the dose and/or the number of sprays may have to be increased in order to ensure the same level of crop protection. Resistance management thus appears crucial to reduce pesticide use, in line with the vision of a more sustainable agriculture that is less dependent on chemical inputs.The Performance network (Arvalis-INRA) has been created in 2004 to provide regional and annual recommendations for the use of anti-septoria fungicides. In 2017, it gathered information from 1007 wheat trials, distributed in the various French cereal basins. These trials were designed to determine the efficacy of different spray programs and their ability to manage resistance. In this thesis, we decided to analyze the Performance dataset as a whole, to understand the determinants of resistance evolution at the regional and field scales. To achieve this, we developed statistical models to quantify the effect of several factors on the observed resistance frequencies from both treated and untreated plots.First, we highlighted and quantified the heterogeneity of resistance selection towards 3 modes of action at the regional scale. Growth rates estimates showed that the different resistances evolved at significantly different rates, with much higher rates for the resistance to strobilurins. We detected contrasted resistance evolutions within the French regions, with a clear disparity between the North and the South of France. Then, we explained these heterogeneities using (i) the regional use of fungicides (i.e. selection pressure), (ii) the proportion of untreated surfaces (i.e. refuges), (iii) yield losses related to septoria leaf blotch (i.e. population size of the pathogen). We showed that fungicide use was a major factor in the observed variability (up to 87 %). Finally, we studied at the field scale the effect of fungicide mixture and dose reduction on selection, which are common anti-resistance strategies used by farmers. We showed that selection is slowed down by the diversity of fungicides used (intra- and inter-mode of action diversity). In addition, as previously at the regional scale, we estimated how the amount of fungicide applied to a plot modulates the selection of different resistances.To conclude, we described, quantified and produced a reference framework to study of large-scale resistance evolution. In addition, we also compared the sustainability of two major anti-resistance strategies at the field scale. These analyses were carried out on spatial and temporal scales unprecedented in the scientific literature. The methods developed are not specific to Z. tritici and our results can be used to improve the prediction of resistance, which is essential to change chemical control practices in agriculture
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.
Texto completo da fonteSteva, Hervé. "Résistance de l'oi͏̈dium de la vigne (uncinula necator (Schw. ) Burr. ) aux fongicides inhibiteurs de la biosynthèse des stérols". Bordeaux 2, 1992. http://www.theses.fr/1992BOR28177.
Texto completo da fonteBastien, Maxime. "Étude de la résistance à la sclérotiniose chez le soya". Thesis, Université Laval, 2013. http://www.theses.ulaval.ca/2013/30341/30341.pdf.
Texto completo da fonteSclerotinia stem rot (SSR), caused by the fungus Sclerotinia sclerotiorum, is one of the most important soybean diseases in Eastern Canada. Using resistant varieties is the most efficient and economic way to repress this disease. However disease pressure in the field fluctuates considerably from year to year according to climatic conditions, thus impeding the identification of resistant material. We developed a reliable and reproducible artificial inoculation method to assess resistance in the greenhouse and in the field. Named the «cotton pad method», it relies upon applying a piece of cotton pad soaked in a mycelial suspension on a floral bud and to measure the ensuing lesion length one week after inoculation. This quick and easy method provides disease ratings similar to the reference method used in Québec and is able to distinguish true resistance from disease avoidance mechanisms. We then used the cotton pad method to evaluate the degree of resistance in a panel of 130 soybean lines representing the genetic diversity present in this species in Quebec. In parallel, we developed a high-throughput genotyping by sequencing method for soybean and used it to genotype the collection. Sequencing provided 266.7 million distinct sequences, which yielded 7,864 SNPs on the 20 soybean chromosomes after several filtering steps. Association mapping performed between the genotype of the lines and their resistance level revealed the presence of four quantitative trait loci (QTLs) associated with SSR resistance. The strongest association was validated in a biparental population generated from a cross between two parents contrasted at this locus. Furthermore, none of the most resistant lines developed so far carries all of the resistance alleles, which suggests that it is possible to develop lines presenting increased SSR resistance. These results are promising for marker assisted or genomic selection.
Germanos, Gaby. "Caractérisation d’un gène de résistance contre la tordeuse des bourgeons de l’épinette (Choristoneura fumiferana) chez l’épinette blanche (Picea glauca (Voss) Moench)". Master's thesis, Université Laval, 2014. http://hdl.handle.net/20.500.11794/25304.
Texto completo da fonteA localized spruce budworm (Choristoneura fumiferana) outbreak that took place in a white spruce plantation (Picea glauca (Voss.) Moench) left some trees almost untouched while many others had severe defoliation. Expression of agene coding for a beta-glucosidase enzyme was identified (Pgβglu-1) and was linked to the accumulation of two acetophenones in the foliage of resistant trees. We propose that the expression variation of Pgβglu-1 involve regulation that is unique to resistant trees. Our results establish a correlation between gene expression, the accumulation of biologically active acetophenones and the most destructive larval instar of the insect. Our results also show that Pgβglu-1expression is genetically transmitted and can be induced. Coding DNA sequences of the gene were obtained but no differences were observed that could differentiate between resistant and non-resistant trees. A deeper understanding of the phenomenon could help in the development of an integrated management aiming to mitigate damage caused during outbreaks.
Abd, Elfatah Hamida Ahmed. "Une approche fonctionnelle de la compétition entre espèces adventices et espèces cultivées : application au cas de Solanum nigrum L. et de la tomate Lycopersicon esculentum Mill". Montpellier 2, 1987. http://www.theses.fr/1987MON20257.
Texto completo da fonteDiabaté, Abdoulaye. "Le paludisme au Burkina Faso : étude de la transmission et répartition géographique de la résistance d'"Anopheles gambiae" SL aux pyréthrinoi͏̈des". Montpellier 2, 2003. http://www.theses.fr/2003MON20026.
Texto completo da fonteLavigne, Jean-Philippe. "Lutte contre les infections bactériennes : de l'optimisation de l'administration d'antibiotiques à l'étude d'un modèle de virulence (Brucella suis)". Montpellier 1, 2004. http://www.theses.fr/2004MON1T015.
Texto completo da fonteNance, Eric. "Localisation chromosomique et expression tissulaire des gènes amplifiés codant les estérases impliquées dans la résistance aux insecticides organophosphorés chez "Culex pipiens"". Montpellier 2, 1991. http://www.theses.fr/1991MON20145.
Texto completo da fontePocquet, Nicolas. "Résistances aux insecticides chez les Culicidae vecteurs en territoires insulaires". Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20006/document.
Texto completo da fonteInsecticide resistance is a natural adaptation phenomenon of insects. When it occurs in a vector population, it compromises vector control interventions, and therefore limits the ability to control the diseases they transmit. Insecticide resistance in Culicidae is widespread throughout the world, and is also found in islands. However, their geographic isolation influences the presence and distribution of resistance alleles. We have worked on four mosquito species in several islands, and we tried to (i) assess the resistance levels and characterize the mechanisms involved, (ii) identify contextual and/or evolutionary factors explaining the presence and distribution of resistance genes in some of these species, and (iii) evaluate new control tools that can be implemented in the specific context of Mayotte island. Our results showed a strong resistance of Culex p. quinquefasciatus to all insecticide families used so far in the Indian Ocean. However, the distribution of resistance mechanisms showed a strong spatial heterogeneity. Indeed, some resistance alleles were not present on all islands and/or not at the same frequencies. In addition, at a more local scale in Mayotte, there were strong differences of resistance status between species. These differences between species and islands are discussed in relation to the influence of local selection pressures and their origins, and to the fitness cost of different alleles. Proposals for modification in vector control practices are set to Mayotte, integrating new tools we have evaluated on the field
Goulois, Joffrey. "Diversité des modes de résistance de cible aux antivitamines K chez les rongeurs". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1048/document.
Texto completo da fonteRodent populations are responsible for many economic and health problems. For these reasons different rodents species are called pests and particularly brown rats, house mice and black rats. Their populations need to be managed. This management involves health and environmental measures strictly necessary but is also based on the use of toxic chemicals. As part of chemical control, the AVKs are currently the most commonly used molecules. These AVKs inhibit blood coagulation and are the cause of fatal bleeding. The pharmacological target of AVK is the VKOR enzymatic activity, encoded by the vkorc1 gene. However, the intensive use of AVKs since the 1950s has led to the development of resistance to these molecules. The target resistance has been well studied in the brown rat, but little is known in the house mouse and the black rat
Lakkis, Sara. "Résistance systémique induite par Pseudomonas fluorescens et Bacillus subtilis chez des génotypes de vigne de différentes sensibilités au mildiou et à la pourriture grise Strengthening Grapevine Resistance by Pseudomonas fluorescens PTA-CT2 Relies on Distinct Defense Pathways in Susceptible and Partially Resistant Genotypes to Downy Mildew and Gray Mold Diseases". Thesis, Reims, 2019. http://www.theses.fr/2019REIMS025.
Texto completo da fonteDowny mildew caused by the oomycete Plasmopara viticola and grey mold caused by the fungus Botrytis cinerea are among the highly threatening diseases in vineyards. The current strategy to control these diseases relies totally on the use of chemical fungicides. The use of beneficial bacteria is arising as a sustainable strategy in controlling various diseases. This can be achieved through the activation of the plants own innate immune system, known as induced systemic resistance (ISR). Such a strategy is effective in controlling grey mold disease, but the efficiency against downy mildew is still in unknown, and the mechanisms underpinning the resistance state remain to be explored. In this study we focused on the capacity of Pseudomonas fluorescens PTA-CT2 to induce ISR in grapevine against P. viticola and B. cinerea by using two grafted cultivars differing in their susceptibility to downy mildew, Pinot noir as susceptible and Solaris as partially resistant. We then examined the differences and similarities of Bacillus subtilis- and P. fluorescens-mediated ISR and priming state after P. viticola challenge. On the basis of the contrasting phenotypic susceptibility of cultivars, we explored mechanisms underlying ISR before and upon pathogen infection. We provide evidence that P. fluorescens induces ISR against P. viticola and B. cinerea by priming common and distinct defensive pathways depending on the basal immunity of genotype. Although P. fluorescens elcits hormonal synthesis and photosynthetis efficiency before infection in both genotypes, our results highlight an important role for salicylic acid (SA)-dependent defense and phytoalexin synthesis, but not JA and ET signaling in ISR against P. viticola in both cultivars. The priming state relies further on the strong expression of HSR gene involved in HR-like cell death in Solaris, whereas in the susceptible cultivar it involves accumulation of ABA, rather than HR-like cell death. The induced ISR against B. cinerea is rather related to the activation of JA/ET signaling, but also to stilbene accumulation and reduction of cell death in both cultivars.The comparative approach between Bacillus subtilis- and P. fluorescens-ISR revealed significant differences in terms of primed defenses against P. viticola. Although both bacteria induce comparable level of ISR by mainly priming SA pathway and stilbene accumulation in both grape varieties, the strong responses are provided by B. subtilis which also induces high expression of the HR-related gene and the accumulation of SA, especially in the resistant hybrid variety. P. fluorescens potentiates to a lesser extent the expression of other SA-related genes and accumulation of ABA in both varieties. These results suggest that B. subtilis- and P. fluorescens-induced ISR against P. viticola could operate through common and distinct mechanisms depending on the basal resistance of grapevine genotype.Further transcriptomic analyses were performed on mock and P. fluorescens-treated Pinot noir after inoculation with B. cinerea and P. viticola, in order to characterize the expression of genes associated to ISR against pathogen with different lifestyle. A large number of differentially expressed genes (DEGs) identified from the RNA-seq data suggests that P. fluorescens-ISR could be associated with priming of several mechanisms depending on the pathogen lifestyle
Hiriart, Jean-Baptiste. "Etude des mécanismes moléculaires mis en jeu dans la résistance à l'infection de plantes transgéniques exprimant la protéine capsidique du virus de la mosai͏̈que chromée de la vigne". Bordeaux 2, 1995. http://www.theses.fr/1995BOR28351.
Texto completo da fonteDenise, Hubert. "Caractérisation chez les trypanosomes africains de protéines ayant une affinité pour les trypanocides existants". Bordeaux 2, 1997. http://www.theses.fr/1997BOR28500.
Texto completo da fonteMarsan-Pelletier, Félix. "Enquête sur la petite herbe à poux (Ambrosia artemisiifolia L) résistante à l'imazéthapyr au Québec". Master's thesis, Université Laval, 2018. http://hdl.handle.net/20.500.11794/35073.
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