Phytate mineralising rhizobacteria are associated to common bean nodulated root

National audienceIn the context of a more sustainable agriculture based on the reduction of mineral fertilizers as Inorganic phosphate, we need to better understand the potential of use of organic soil P as P source for plants that acquire P as inorganic P, exclusively. Within organic P, Inositol phosphates (phytates) are the dominant class of organic phosphorus (P) compounds in soils; it is generally estimated to contribute to at least 50% of total organic soil P. In order to become available for plants organic P must be mineralized by phosphatases, mostly originated from the soil microbial community. Phytases are the most active phosphatases for the dephosphorylation of Inositol phosphates. The aim of this work is to characterize the functional microbial community involved in the mineralization of phytate in the rhizosphere of a leguminous plant. Phytate-mineralizing bacteria were isolated using a selective media from the rhizosphere of common bean (Phaseolus vulgaris) growing in soil. The density of phytate-mineralizing bacteria was higher in the rhizosphere of beans cultured on low P soil compared to a P-fertilized soil, and represented 1% of the microbial community in the rizosphere of common bean. The phytate-mineralizing bacteria selected in this work belonged to Enterobacter, Pseudomonas and Pantoea families according to the sequencing of 16S DNA.The capacity of those isolates to release inorganic P (Pi) from Na-phytate and to use phytate as a sole P source was confirmed in broth. It is concluded that phytate-mineralizing bacteria can be found in the rhizosphere of a nodulated legume and that communities of phytate-mineralizing bacteria are more important when the rhizosphere is deficient in P