Studies on the Biochemistry of Tetrahymena III. Strain Differences

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Abstract
Two sources of 6 strains of T. geleii and 2 strains of T. vorax are discussed and the literature concerning them summarized. The ability of these strains to ferment 27 carbohydrates was tested and a diagnostic system proposed on the basis of the reactions in galactose, lactose, and starch. Preliminary studies of amino acid requirements indicate that arginine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophane, and valine may be regarded as essential for all strains. Only the 2 strains of T. vorax gave normal growth in a mixture of the above-mentioned amino acids. Replacement of glycine by serine permitted growth of all strains. T. geleii E and T-P failed to give normal growth in a mixture of 19 amino acids due to inhibitory effects of some of the amino acids. In the presence of the stimulatory amino acids (cystine, glycine, and serine) certain of the essential amino acids seem to be synthesized. The dispensable amino acids (alanine, aspartic acid, glutamic acid, hydroxyproline, proline, and tyrosine) are, in general, inhibitory. Inhibition by the dispensable amino acids may be released by the stimulatory amino acids either singly or in combination. None of the 8 strains of ciliates studied require thiamine. The strains differ in the intensity of the purplish coloration of the medium (1% proteose-peptone) produced. All strains differ either in carbohydrate fermentation or in reaction to amino acids. Larger differences are found between the 6 strains of T. geleii than between the 2 strains of T. vorax.