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J Bacteriol. 1965 September; 90(3): 748-754
Copyright © 1965 American Society for Microbiology. All Rights Reserved.

Free Amino Acids in Serine-Antagonized Cells of Tetrahymena pyriformis¹

Human Nutrition Research Division, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland
Department of Microbiology, University of Maryland, College Park, Maryland

ABSTRACT

WRAGG, JUNE B. (Agricultural Research Service, Beltsville, Md.), HOWARD REYNOLDS, AND MICHAEL J. PELCZAR, JR. Free amino acids in serine-antagonized cells of Tetrahymena pyriformis. J. Bacteriol. 90:748–754. 1965.—Growth inhibition of Tetrahymena pyriformis by L-serine in a chemically defined medium was reversed by L-arginine in a manner which resembled competitive antagonism. Composition of the free amino acid pools from cells grown in either a balanced amino acid mixture or a mixture with serine concentrations which inhibited growth suggested an antagonism by serine with energy-yielding reactions. Growth in media with excess serine resulted in the accumulation of higher concentrations of free cellular amino acids and an apparent increase in the rate of conversion of arginine to ornithine, as compared with growth in the balanced medium. The results suggested that serine or a metabolic product of serine interferes with the formation of pyruvic acid. In the presence of high levels of serine, arginine appeared to be metabolized more rapidly and to be spared when alanine, aspartic acid, or glutamic acid was added to the unbalanced medium.

¹ Presented in part at the Annual Meeting of the American Society for Microbiology, Washington, D.C., 3 to 7 May 1964. A portion of this material was submitted by June B. Wragg in partial fulfillment of the requirements for the M.S. degree, University of Maryland, College Park.