Impact de la réponse stringente sur la mutabilité de Streptomyces coelicolor et Streptomyces ambofaciens au cours de la différenciation

Abstract : In nature, organisms are constantly subjected to chemical, physical or nutritional variations of the environment. The modulation of the mutation rate constitutes one of the mechanisms contributing to the adaptation of bacterial species to rapid environmental modifications. The aim of this work was to highlight the influence of environmental factors on the genetic instability characterized in Streptomyces species. Through the study of S. ambofaciens and S. coelicolor mutants, not pigmented, unable to sporulate and produced during the aerial mycelium growth, we showed that a limitation in amino acids constituted a mutagen condition. Indeed, on amino acid-limited media, the production of these mutants was strongly increased. A mutation in their whiG or whiH genes, two genes intervening in the first stages of the sporulation process, was frequently detected. We could highlight, via the study of the relA mutant of S. coelicolor, the existence of a link between stringent response, the physiological response induced during an amino acid limitation, and increase in the mutability of these genes. There is thus a relation between a nutritive limitation and an increase in genetic instability via the establishment of a local or global mutator state, initiated by the induction of the stringent response. The produced mutants could contribute to the survival of the colony during an amino acid limitation metabolising substances different from the rest of the colony or allowing the release of nutrients, food for the neighbour cells.
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Magali Genay. Impact de la réponse stringente sur la mutabilité de Streptomyces coelicolor et Streptomyces ambofaciens au cours de la différenciation. Bactériologie. Université Henri Poincaré - Nancy 1, 2006. Français. ⟨NNT : 2006NAN10123⟩. ⟨tel-01754310⟩

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