Phosphorus-31 nuclear magnetic resonance spectroscopy was used to estimate the levels of polyphosphates and to probe their intracellular environment in the ectomycorrhizal fungi Cenococcum graniforme Ferd. & Wing, and Hebeloma crustuliniforme (Bull.) Quel. Polyphosphate content was a function of the growth phase and nitrogen content in the medium, lowest in rapidly growing mycelia, highest in older and N-starved cultures. During phosphorus depletion the polyphosphate store was mobilized; degradation of the polymer was rapid in H. crustuliniforme, whereas it was slower in C. graniforme. This difference between the two fungi might be related to differences in the intracellular physical state of polyphosphates.
Measurements of nuclear magnetic relaxation parameters, such as resonance line widths and spin-lattice relaxation times, T1, have been carried out in model systems and in intact mycelia with the aim of characterizing the physical state of polyphosphates. The intracellular T1 of inner P of polyphosphates was dramatically shorter than that in the culture medium. Polyphosphate relaxation may result from a combination of partial immobilization of the polymer by cellular components and interaction with paramagnetic ions.
On the basis of these data, it is suggested that polyphosphates exist in ectomycorrhizal fungi as aggregates with reduced correlation time. A more fluid state of polyphosphates in H. crustuliniforme than in C. graniforme might allow their rapid degradation by polyphosphates.