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

Abstract

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