³¹P NUCLEAR MAGNETIC RESONANCE STUDY OF INTRACELLULAR PHOSPHATE POOLS AND POLYPHOSPHATE METABOLISM IN <i>HETEROSIGMA AKASHIWO</i> (HADA) HADA (RAPHIDOPHYCEAE)¹

Abstract

ABSTRACT The effects of starvation and subsequent addition of phosphate‐containing medium on the phosphate metabolic intermediates were studied by 31 P‐NMR spectroscopy of perchloric acid extracts and intact cells of Heterosigma akashiwo (Hada) hada. When orthophosphate in the medium was completely depleted the medium was enriched with orthophosphate (4.5 μM). In the phosphate starved condition, the P cell quota was 76 fmol‐cell −1 and the major components of phosphate intermediates were phosphodiester, sugar phosphate and orthophosphate (P i ) After addition of P i' rapid uptake of P i was observed and the P cell quota increased to 108 fmol. cell −1 in 2 h, 134 fmol. cell −1 in 5 h and 222 fmol. cell −1 in 1 day after addition of phosphate. The 31 P‐NMR spectrum indicated that a major portion of P was stored as polyphosphate, in which the average chain length of polyphosphate increased from 10 to 20 phosphate residues in one day after addition of P i‐