Nutritional stress in Tetrahymena relieved by addition of hemin or phospholipids

Summary The ciliate Tetrahymena thermophila was grown in a synthetic nutrient medium at various amino acid concentrations. Before the beginning of the experiments the cells were starved for 4 h in a pH buffer. They were inoculated at an initial density of only 250 cells per ml. Under these conditions the cells grew and multiplied at only the two highest amino acid concentrations used. Hemin or phospholipids were found to stimulate cell growth at the lower amino acid concentrations. The mechanism behind this stimulatory effect is unknown, but may be connected with the maintenance of an adequate energy flow under adverse conditions. These additions represent an improvement of the synthetic medium for Tetrahymena.Abbreviations PPYS proteose peptone, yeast extract, and salts medium