RESTING SPORE FORMATION AND PHOSPHORUS COMPOSITION OF THE MARINE DIATOM CHAETOCEROS-PSEUDOCURVISETUS UNDER VARIOUS NUTRIENT CONDITIONS

The marine diatom Chaetoceros pseudocurvisetus was used for a study of resting spore formation and cellular phosphorus composition. Resting spores were found in any culture medium with ample silica, including nitrogen limited, phosphorus limited and nutrient replete conditions. Resting spores protected themselves with thick silica walls, so that vegetative cells required about 3 pmol cell(-1) of additional silica to form resting spores. Phosphorus compounds in the cells were divided into eight fractions: nucleotide-P, orthophosphate, acid soluble polyphosphate, sugar phosphate, nucleic acid-P, acid insoluble polyphosphate, lipid-P and residual-P. The sum of orthophosphate, sugar phosphate and nucleic acid-P comprised over 65% of the total phosphorus in cells under any culture conditions. Sugar phosphate was the most variable component, being most abundant in vegetative cells and least abundant in resting spores.