| Abstract: | Log phase cultures of Tetrahymena pyriformis W excrete orthophosphate, a purine, and a pyrimidine when suspended in a non-nutrient buffered medium. Ribonucleic acid has been established as the primary source of these catabolic products. Thirty per cent of the total cellular RNA was degraded in three hours under the conditions of growth and suspension employed. The size of the phosphorus pools of these ciliates was determined during the period of RNA degradation; the internal acid-soluble organic phosphate and the cellular orthophosphate pools remained constant for five hours at 20% and 5% of the total cell phosphorus respectively. The ultraviolet-absorbing materials excreted with the orthophosphate were identified as hypoxanthine and uracil. A pentose, presumably ribose, was excreted in small quantities, but was not equivalent in amount to the orthophosphate and did not parallel the pattern of release of the anion. The excretion of orthophosphate, hypoxanthine, and uracil is correlated with the catabolism of RNA as it has been demonstrated in these cells. |
