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Abstract
SUMMARY:Paramecium aurelia, var. 4, stock 47.8 (sensitive) grown in an axenic medium required the following amino acids: dl-tyrosine, l-phenylalanine, l-tryptophan, dl-methionine, dl-threonine, l-leucine, dl-isoleucine, l-lysine, l-histidine, l-arginine, and dl-serine. dl-valine, l-proline and glycine were synthesized at a slow rate. Tyrosine, methionine and serine were required by stock 51.7 (sensitive). Other essential metabolites required by stock 47.8 (s) were thiamine, riboflavin, folic acid, nicotinic acid, pantothenic acid, and possibly pyridoxal. 2,6-diaminopurine inhibited growth at concentrations as low as 1–4 μg./ml. The growth rates (expressed as final population density/ml./transfer) of various stocks in identical media are different. An apparent correlation was found to exist between the growth rates and the chromosome number of these stocks, those with the largest chromosome number attaining the highest population density.
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