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Abstract
SUMMARY: The power of fermentation by yeast cells was decreased when the cultures were grown in media deficient in any of seven essential growth factors. A rapid increase in the rate of fermentation upon the addition of a growth factor was obtained in every case except that of inositol, where the response was much slower. The absence of a nitrogen source decreased the response to biotin, pantothenic acid or pyridoxin to a much greater extent than to aneurin or nicotinic acid. Differences were noted also in the behaviour of the two groups towards sodium azide, which can be explained on the assumption that biotin, pantothenic acid and pyridoxin affect fermentation only in a relatively indirect manner.
The decrease in the power of fermentation produced by pyridoxin deficiency was not observed until the pyridoxin content of the cells was only about one-fifth of the normal. Such yeast showed also an enhanced Pasteur effect. Pyridoxin deficiency produced no decrease in the proportion of glucose assimilated by resting cells.
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