Strategies of organic phosphorus recycling by soil bacteria: acquisition, metabolism, and regulation.

Critical to meeting cellular phosphorus (P) demand, soil bacteria deploy a number of strategies to overcome limitation in inorganic P (P i ) in soils. As a significant contributor to P recycling, soil bacteria secrete extracellular enzymes to degrade organic P (P o ) in soils into the readily bioavailable P i . In addition, several P o compounds can be transported directly via specific transporters and subsequently enter intracellular metabolic pathways. In this review, we highlight the strategies that soil bacteria employ to recycle P o from the soil environment. We discuss the diversity of extracellular phosphatases in soils, the selectivity of these enzymes towards various P o biomolecules and the influence of the soil environmental conditions on the enzyme's activities. Moreover, we outline the intracellular metabolic pathways for P o biosynthesis and transporter-assisted P o and P i uptake at different P i availabilities. We further highlight the regulatory mechanisms that govern the production of phosphatases, the expression of P o transporters and the key metabolic changes in P metabolism in response to environmental P i availability. Due to the depletion of natural resources for P i , we propose future studies needed to leverage bacteria-mediated P recycling from the large pools of P o in soils or organic wastes to benefit agricultural productivity.