Abstract
All attempts to grow Tetrahymena geleii in a medium of known composition have, so far, failed. Failure to obtain growth in anything but peptones led Lwoff 1 to formulate the hypothesis that the ciliate requires polypeptides and cannot utilize free amino acids. Earlier 2 he had hinted that the failure of growth in a mixture of silk peptone, fibrin peptone and gelatin, which contains all the known amino acids, is the result of the lack of some supplementary substance. Gelatin 3 will support growth if supplemented with a small amount of yeast extract; indeed, it is stated 4 that transplantable growth is obtained in gelatin plus thiamin and riboflavin. Silk peptone gives slight, but transplantable, growth if thiamin is added. 5
It is clear, then, that the question of the amino acid requirement of T. geleii cannot be answered until more is known of the supplementary needs.
In order to discover the vitamin (or supplement) requirements, a basal medium is necessary. Since it had been found that the ciliate will grow well in a 1% solution of crude casein (Eimer and Amend), a similar solution of Casein-Harris (free from fat and water soluble vitamins) was tested. It gave no growth beyond the first or second transplant.
Slight improvement in growth was noted upon the addition of thiamin to this medium. All possible combinations of thiamin, riboflavin, nicotinic acid, pyridoxin, pantothenic acid, biotin (as a concentrate) and inositol† were added. Growth was better in the media containing riboflavin and pyridoxin in addition to thiamin, but it was slow and never reached the concentration obtained in crude casein. It was evident that some other factor is required for optimum growth. The possibility of toxicity of the medium was eliminated, since good growth occurred upon the addition of 0.1% yeast concentrate (Yeast Vitamin Harris) to the vitamin-free casein, whether or not other supplements were present.
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