Vers la compréhension des dialogues microbiens dans les écosystèmes du sol : étude de l'intéraction entre Streptomyces et Pseudomonas

Abstract : Streptomyces are common bacteria in temperate forest ecosystems, which inhabit various ecological niches such as plant rhizosphere and mycorrhizosphere, as well as mineralosphere. In these niches, they interact with many other bacterial genera and different symbiotic, pathogenic and saprotrophic fungi. We have initiated a study on interaction between two soil model bacteria strains Streptomyces ambofaciens ATCC23877 and Pseudomonas fluorescens BBc6R8. Cocultures experiments on different agar media have revealed that each bacteria affects the production of secondary metabolites in the other partner. Thus, P. fluorescens inhibits the ability of S. ambofaciens to produce kanamycin, a "ping-pong effect" was highlighted. On the other hand, on iron deficient medium, P. fluorescens is able to use the desferrioxamines and coelichelin produced by S. ambofaciens as xenosiderophores and does no longer produce its own siderophores, pyoverdin and enantio-pyochelin. In another way, during pairwise co-culture experiments, Pseudomonas fluorescens BBc6R8 was shown to prevent the production of the diffusible blue pigment antibiotic [gamma]-actinorhodin by Streptomyces coelicolor A3(2) M145 by acidifying the medium through the production of gluconic acid. Other fluorescent Pseudomonas strains and the opportunistic pathogen Pseudomonas aeruginosa PAO1 also prevented the [gamma]-actinorhodin production in a similar way. Altogether these results prompt us to propose some hypotheses on the ecological significance of these three interactions by replacing them in the soil ecosystem context
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Justine Galet. Vers la compréhension des dialogues microbiens dans les écosystèmes du sol : étude de l'intéraction entre Streptomyces et Pseudomonas. Bactériologie. Université de Lorraine, 2014. Français. ⟨NNT : 2014LORR0292⟩. ⟨tel-01751378⟩

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