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Abstract
SUMMARY: Euglena gracilis Z showed an absolute requirement for vitamin B1 for growth. Increase of cell number in vitamin B1-deficient cultures occurred on the addition of vitamin B1 and depended on the amount added. The phosphate esters of vitamin B1 also supported growth. E. gracilis cells exhaustively took up vitamin B1 within about 2 h of addition. Of the total amount of vitamin B1 taken up, as much as 96% existed in the free form irrespective of the forms added. The addition of 4-amino-5-hydroxymethyl-2-methylpyrimidine, but not 5-(2-hydroxyethyl)-4-methylthiazole, to the vitamin B1-deficient cells enhanced cell number at the same rate as the addition of vitamin B1, indicating that E. gracilis Z is unable to synthesize the pyrimidine moiety of vitamin B1.
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