Studies on synchronously dividing cultures of Euglena gracilis Klebs (strain Z). II. Patterns of biosynthesis during the cell cycle

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  • LELeland N. Edmunds
    Leland N. Edmunds
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Abstract
Dry weight, total protein, chlorophyll a, carotenoids, soluble protein, RNA, DNA, and total phosphorus were determined at intervals of two hours during synchronous growth of Euglena at a cell concentration of 5–10 × 104 cells/ml maintained by periodic dilution. Detailed analyses of the soluble proteins (DEAE‐cellulose fractionation) and of the intracellular distribution of phosphorus were made also. In general, a linear doubling of each of these major components occurred during the light period; there was no net synthesis during the dark. Since cell number doubled during the dark period, a halving of the amounts of the parameters in each cell occurred. The most notable exception was the stepwise synthesis of DNA during the light period: DNA replicated during the last 6 hr only of the light period, commencing at 8 hr after the onset of light. Although DNA replication was a necessary condition for cell division to occur, it was not necessarily a sufficient one. It was found that different absolute rates of synthesis exist for the different compounds, with a doubling of a given parameter sometimes being completed before the end of the light period.

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