Polyphosphate metabolism in the alga Dunaliella salina studied by 31P-NMR

Polyphosphate synthesis and the state of the intracellular polyphosphates in the unicellular green alga Dunaliella salina were studied using in vivo 31P-NMR spectroscopy. By perfusing phosphate-depleted algal cells trapped inside agarose beads with orthophosphate (Pi) containing medium, we were able to follow the process of polyphosphate synthesis in whole, living cells. The results suggest that, in Dunaliella, low molecular weight, probably cyclic, polyphosphate intermediates are synthesized from Pi, and are then condensed to high molecular weight polymers. Studies of the intracellular organization of the polyphosphates by electron microscopy and solid-state NMR techniques indicate that most of these polymers are stored in the cell in a soluble form, and not in solid-like structures.