The amino acid composition and nitrogen metabolism of Tetrahymena geleii.

The nitrogen composition and metabolism of the typical animal microorganisms are relatively unknown. This is true largely because of the past unavailability of the Protozoa either in pure culture or in synthetic media. The ciliated protozoan, Tetrahymena geleii, is unique in that it has been available in pure culture for some time and recently (1949) it has been grown in synthetic medium (2). Investigations of bacterial amino acid composition have led to the proposal that the growth requirements of a microorganism are reflected in its cellular composition (3, 4). This may now be investigated for the Protozoa. Additionally, previous work (5, 6) has shown that the maintenance of T. geleii strain E in a synthetic medium will alter certain nutritional requirements and metabolic capacities of the organism; i.e., an adaptation occurs. Thus a determination of the effects of medium composition and culture adaptation on the amino acid composition of this organism would further characterize the process of adaptation to a synthetic medium. Also it would make possible a comparison with the composition of other microorganisms (4, 7-12) and higher animals (2, 13). In this work, the chief concern has been with the nitrogen composition of T. geleii. However, the gross features of the nitrogen metabolism have also been determined. Adaptation to a synthetic medium has produced significant changes in the amino acid and nucleic acid composition of this protozoan cell. In agreement with the work of Lwoff (2), complete analyses of culture filtrates have demonstrated that this aquatic organism is primarily ammonotelic.