Application of polyphosphate metabolism to environmental and biotechnological problems

The synthesis and degradation of polyphosphate (polyP) are influenced by th e energy state of the cell and extracellular phosphate levels. The import o f excess phosphate and its incorporation into polyp under phosphate- and en ergy-rich growth conditions allows organisms to survive when phosphate or e nergy are depleted. Under phosphate-starvation conditions, phosphate can be recovered from polyp by hydrolysis. When the organism is energy starved, e nergy can be recovered either by regenerating the high-energy phosphoanhydr ide bond donor (ATP in most cases) or by hydrolysis of polyP and subsequent secretion of orthophosphate to recharge the transmembrane proton gradient. Understanding how the energy state of the cell and environmental phosphate levels affect polyP metabolism is essential to improving such environmenta l processes as enhanced biological phosphorus removal, a treatment process that is widely used to remove excess phosphate from wastewater. Manipulatio n of the genes responsible for polyP metabolism can also be used to improve gene expression from phosphate-starvation promoters and to remove heavy me tals from contaminated environments.