Studies on the Biochemistry of Tetrahymena

Abstract

Tetrahymena requires an exogenous source of purine and pyrimidine for growth. None of the natural purines tested, except guanine, would support growth. Guanylic acid was slightly more active on a molar basis than guanosine and twice as active as guanine. Adenine, adenylic acid and hypoxanthine spared guanine, but uric acid and thymidine were without activity. Xanthine possessed low sparing activity at high concns., possibly due to a slight chemical contamination, since synthetic xanthine exhibited none. Uracil and cytadylic acid can serve as the pyrimidine source and are nearly equal in activity, but cytosine and thymine are inactive. Diammonium uridylate and cytocine exhibited the same activity as cytadylic acid. Thiamine pyrimidine is slightly inhibitory at high levels.