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In the process of the incorporation of orthophsphate into protein and other cell constituents, the role of inorganic polyphosphate and RNA-polyphosphate complex and the correlation between them were pursued by analyzing the contents of ³²P and total P in various fractions of Chlorella cells, which had been uniformly labeled with ³²P before the inoculation in a normal "cold" medium or P-free medium during the culture. The effects of ionizing radiation and various micronutritional-element deficiencies on the phosphate incorporation into, and biosynthesis of, protein and other introgenus compounds in the cells were also observed. When the uniformly ³²P-labeled algae were grown in a normal "cold" medium the contents of ³²P in the fractions of protein, DNA and RNA-polyphosphate complex increased, but those in the fraction of acid-insoluble polyphosphate decreased. On the other hand, amount of ³²P in the fraction of RNA was almost unchanged in spite of rapid increase of the total P. In the growing period of ³²P-labeled algae in a P-free medium, amounts of ³²P in the fractions of DNA, protein and lipid increased, while those in the fractions of RNA-polyphosphate and inorganic polyphosphates decreased. When the algal cells were irradiated with about 70,000r of gamma-rays before the inoculation in the medium, amounts of phosphate in the fractions of DNA, RNA, nucleotides and protein decreased during the culture, compared with those of the control. However, the phosphate content in the fraction of acid-insoluble polyphosphate of the irradiated cells increased than those of the control. In the growing period of the algae in a Mo-free, medium, amounts of acid-soluble total phosphate and nucleotides of the cells increased, while the amounts of residual protein and RNA decresed compared with those of the normal cells. Amounts of alkali-labile protein and phospholipid of the cells grown in a B-free medium decreased, whereas amount of phosphate in acid-soluble fraction increased compared with the control. In general, the contents of protein and RNA in each microelement deficient cells decreased more or less, compared with those in the normal cells.
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