Déterminisme de la diversité bactérienne rhizosphérique des hyperaccumulateurs de nickel

Abstract : Knowledge of the microbial diversity in ultramafic areas is essential to establish the ecological functioning of these environments, which display high level of Ni and are characterized by the presence of particular plants, e.g. Ni hyperaccumulators. The rhizosphere of these plants promotes a high proportion of Ni resistant bacteria that can act on plant nutrition and soil physicochemical properties. The first challenge of this thesis was to understand the bacterial rhizosphere diversity of Ni hyperaccumulators. The second was to test the interest of PGPR (Plant Growth Promoting Rhizobacteria) strains in order to improve agromining based on rhizobacteria and Ni hyperaccumulators interactions. The approach was based on two-contrasted climatic areas prospection and on high-throughput sequencing analyzes. Tests on culture of hyperaccumulator plants inoculated were also conducted. The results show that the determinism of this bacterial diversity is variable according to the spatial scale. On a global scale, the vegetation type, indirectly influenced by the climate, is the major factor structuring bacterial communities. The direct influence of the climate (temperature and humidity) on bacterial diversity is significant but lower. At the scale of a climatic region, the physic-chemistry of ultramafic soils structures and determines the rhizosphere bacterial community diversity. Finally, the inoculation of highly Ni bioaccumulative PGPR strains modifies the Ni dynamic in the soil, demonstrating that there is a competition for this metal between the inoculated bacteria and the hyperaccumulator plant. In conclusion, the rhizosphere bacterial community diversity is dependent on the considered spatial scale. Furthermore, these results emphasize how the choice of the PGPR strain to inoculate is important in order to improve Ni agromining.
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Séverine Lopez. Déterminisme de la diversité bactérienne rhizosphérique des hyperaccumulateurs de nickel. Biodiversité et Ecologie. Université de Lorraine, 2018. Français. ⟨NNT : 2018LORR0335⟩. ⟨tel-02323036⟩

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