Impact of Ectomycorrhizosphere on the Functional Diversity of Soil Bacterial and Fungal Communities from a Forest Stand in Relation to Nutrient Mobilization Processes |
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Authors: | Christophe Calvaruso Marie-Pierre Turpault Elisabeth Leclerc Pascale Frey-Klett |
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Institution: | (1) INRA, UR1138 “Biogéochimie des Ecosystèmes Forestiers”, Centre INRA de Nancy, 54280 Champenoux, France;(2) INRA, UMR1136 “Interactions Arbres-Microorganismes”, Centre INRA de Nancy, 54280 Champenoux, France;(3) ANDRA, Direction Scientifique/Service Transferts, 92298 Chatenay-Malabry, France |
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Abstract: | The ectomycorrhizal symbiosis alters the physicochemical and biological conditions in the surrounding soil, thus creating
a particular environment called ectomycorrhizosphere, which selects microbial communities suspected to play a role in gross
production and nutrient cycling. To assess the ectomycorrhizosphere effect on the structure of microbial communities potentially
involved in the mobilization of nutrients from the soil minerals in a poor-nutrient environment, we compared the functional
diversity of soil and ectomycorrhizosphere bacterial communities in a forest stand. Two hundred and sixty-four bacterial strains
and 107 fungal strains were isolated from the bulk soil of an oak (Quercus petraea) stand and from oak–Scleroderma citrinum ectomycorrhizosphere and ectomycorrhizae, in two soil organo-mineral horizons (0 to 3 cm and 5 to 10 cm). They were characterized
using two in vitro tests related to their capacities to mobilize iron and phosphorus. We demonstrated that the oak–S. citrinum ectomycorrhizosphere significantly structures the culturable bacterial communities in the two soil horizons by selecting
very efficient strains for phosphorus and iron mobilization. This effect was also observed on the diversity of the phosphate-solubilizing
fungal communities in the lower soil horizon. A previous study already demonstrated that Laccaria bicolor–Douglas fir ectomycorrhizosphere structures the functional diversity of Pseudomonas fluorescens population in a forest nursery soil. Comparing to it, our work highlights the consistency of the mycorrhizosphere effect
on the functional diversity of bacterial and fungal communities in relation to the mineral weathering process, no matter the
fungal symbiont, the age and species of the host tree, or the environment (nursery vs forest). We also demonstrated that the
intensity of phosphorus and iron mobilization by the ectomycorrhizosphere bacteria isolated from the lower soil horizon was
significantly higher compared to that which was isolated from the upper horizon. This reveals for the first time a stratification
of the functional diversity of the culturable soil bacterial communities as related to phosphorus and iron mobilization. |
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