Purposed work is in the context of the forth-coming P crisis that will limit biomass production. To face this crisis and to increase the sustainability of agricultural production, especially in the developing countries where the access at mineral P is extremely limited, the present study proposes to find innovative strategies aiming at better exploiting the soil organic/inorganic P pool. The focus of this research activity will be on unavailable P either mineral/organic, which constitutes a major fraction of soil P and that is very poorly usable by plants because plants are hardly able to secrete acids/phytases, required to hydrolyse/solubilize insoluble inorganic/organic P compound to release free phosphate (Pi), the sole source of P taken up by living organisms. In contrast to plants, bacteria can be able to use both unavailable P sources in pure culture, either by releasing organic acids/phytases and Pi in the external medium (Gram+ bacteria, such as Bacillus sp.) or in the periplasmic space (Gram- bacteria, such as Pseudomonas sp.).

Our main strategy will rely on a better exploitation of the biological complexity between those bacteria, their grazers such as bacterivorous nematodes known as the microbial loop, together with the role of the mycorrhizal symbiosis. After the establishment of the main factors regulating the effects of the microbial loop to the benefit of plant P nutrition in simplified conditions in the laboratory. The effort will be to find indicators (i.e. nematofauna description) and possible drivers for ecological intensification of plant P nutrition in ecosystems with low availability P.