The Grazing Activity of Sp. Drives Phytate Mineralisation Within Its Trophic Relationship with Bacteria

The microbial loop has been suggested as an alternative route for better utilization of phytate, a poorly available P source to plants. We hypothesized that bacterial grazer activity might dramatically enhance bacterial migration and proliferation, increasing the probability of phytate hydrolysis by bacterial phytases and, thus, phytate mineralization and release of free phosphate. We tested this hypothesis in a two-compartment system with a solid medium containing phytate or free phosphate as the source of P. Two bacterial species, 168 or sp., with or without bacterial grazing nematodes belonging to sp. previously fed on each of the bacterial species, were inoculated at a single point in the medium. Whatever the P source, nematode migration within both zones allowed the proliferation of bacteria. However, 168 was more efficient in using phytate than sp. since the highest bacterial cell density and free phosphate concentrations were reached by sp. fed on 168. The grazer activity seemed to be crucial to enhance phytate mineralization, despite sp. showing a higher preference to feed on sp. This study provides new insights into the effects of bacterial grazer activity on phytate mineralization.