Studies on the Biochemistry of Tetrahymena

Abstract

Introduction.-Previous studiesl-7 have shown that the ciliated protozoan, Tetrahymena, has nutritional requirements very similar to animals in general. This similarity is especially striking in regard to amino acid requirements where the ten essential amino acids of the dog, man, etc., have.been shown to be essential also for Tetrahymena. Inasmuch as this protozoan possesses characteristics which make its culture in the absence of all other organisms relatively simple, it has been possible to investigate rather precisely the effects of various substances on its metabolism. Biochemical studies of this nature on other animals have been complicated and even vitiated by contaminating microorganisms of unknown synthetic abilities. This report deals with the growth responses of Tetrahymena to varying concentrations of the essential amino acids and to serine, and includes the results of tests involving availability of "natural and unnatural isomers. Experimental.-The organism used in this investigation was Tetrahymena geleii W grown in pure (bacteria-free) culture. The general techniques have been previously reported." 4, 8 Dose-response curves were constructed for each of the essential amino acids, and for the stimulatory amino acid, serine, by adding graded amounts to a base medium containing the other ten in the proportions found in gelatin (table 1, medium II) together with growth factors, dextrose and salts. The minimum concentrations which permitted optimum growth under these conditions were combined, but the nitrogen level was then inadequate so these amounts were increased fivefold (medium III, table 1). Dose-responses were then studied using these new proportions. This medium was also used in studies on the availability of unnatural isomers. The factor II preparations, which are necessary for the growth of this organism9' 10 were of two types. The one prepared from cerophyl, as

The Effects of Nutrient Deficiencies and Analogs on the Cell and Nuclear Volume of Tetrahymena pyriformis*

“…In this case later addition of the analog may be almost ineffectual ( 17). Furthermore, the present experiments are not directly comparable to those of Kidder and Dewey ( 6,8,9) since this research utilizes as a-measure growth rate rather than maximum amount of growth.…”

“…Five out of the eleven essential amino acids were chosen for the amino acid deficiency studies; arginine, leucine, methionine, phenylalanine, and serine. The corresponding analogs used were: canavanine sulfate in a 2 to 1 ratio writh arginine, D-leucine in a 1 to y2 ratio with L-leucine, ethionine in a 3 to 1 ratio with methionine, p(Z-thienyl)-alanine in a 2 to 1 ratio with phenylalanine and +(2-thienyl)-serine in a 2 t o 1 ratio with serine (6).…”

Effect of Type of Carbohydrate on Growth and Protein Synthesis by Tetrahymena pyriformis

“…I t appeared therefore that T . pyrijormis, with its recognized mammalian-like nutritional requirements (6,11,12), should serve as a useful tool for investigatinq relationships among type of carbohydrate. cell growth, and nitrogen utilization.…”