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La réponse au stress chez les bactéries : réponse au stress métallique chez Pseudomonas putida et au stress rencontré en cours d’infection de plante chez le phytopathogène Dickeya dadantii

Abstract : Environmental bacteria have to deal with a number of stresses in their livingenvironment. The bacteria have to adapt quickly to changes in temperature, osmolarity,pH changes or nutrient deficiencies in order to survive and thrive in their naturalenvironment. This thesis work is related to the study of stress response inenvironmental bacteria by taking the example of stress caused by metals in thebacterium Pseudomonas putida model and stress encountered during plant infection inthe phytopathogen Dickeya dadantii. The presence of an excess of metal ions as well asthe defences of a plant on a phytopathogen both cause oxidative stress and can causemembrane and protein alteration. These stresses, at first sight distant, could thus inducesimilar response mechanisms in bacteria. Most stress resistance studies in bacteriafocus on the study of over- or under-expressed genes and may then lack genesimportant for the response to a given stress whose expression remains unchanged. Inorder to identify new metal stress resistance genes in P. putida and newresistance/virulence factors in D. dadantii phytopathogen, a Tn-seq (Transposon-Sequencing) screen was performed using very dense mutant banks. Both screenshighlighted the major role of transcription regulators as well as the importance of effluxmechanisms in the response to stress. Both screens also highlighted the importance ofamino acid and nucleic acid biosynthesis pathways. Finally, many genes with unknownfunction participate in the survival of both bacteria in stress conditions. The resultsobtained could lead to the development of new antimicrobials in D. dadantii. Themechanisms of resistance to metals and antibiotics may be similar. Our work isimproving our understanding of metal resistance mechanisms and could lead to newmolecules with antimicrobial activity
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Kévin Royet. La réponse au stress chez les bactéries : réponse au stress métallique chez Pseudomonas putida et au stress rencontré en cours d’infection de plante chez le phytopathogène Dickeya dadantii. Microbiologie et Parasitologie. Université de Lyon, 2018. Français. ⟨NNT : 2018LYSE1206⟩. ⟨tel-02426000⟩

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