Culture Variation in Tetrahymena

Abstract

T. geleii. strain E, tends to adapt toward a medium deficient in certain nutrilites that have otherwise been considered essential. This phenomenon has resulted in considerable variation where the nutritional requirements are under investigation. These variations have been characterized with respect to the nutritional requirements for certain amino acids. Two exptl. types were observed: (1) blank-adaptive growth and (2) substitute-adaptive growth. In type 1 the organisms grown in synthetic media were observed to grow to some extent in a medium deficient in a single amino acid (arginine, serine). In type 2 the variant organisms grew in the presence of previously nonutilizable amino acid substitutes (citrulline, "ketoisoleucine"). Several possible explanations are considered, and the significance of the phenomenon for research on Tetrahymena is emphasized.