Use of 8-hydroxyquinoline to enrich for temperature-sensitive mutants of Tetrahymena

The effects of the chelating agent 8-hydroxyquinoline (Hq) on Tetrahymena thermophila were examined. Cell division was completely inhibited by 5 micrograms of Hq per ml. At this concentration deoxyribonucleic acid, ribonucleic acid, and protein syntheses were also completely and nonselectively inhibited. The inhibition was reversible after 6 h of Hq treatment. At concentrations above 20 micrograms/ml a 10,000-fold decrease in survival as seen after 2 h in the drug. The sensitivity of Tetrahymena to Hq was found to be dependent upon cell concentration, wild-type strain, medium, and length of time the culture is at 38 degrees C before Hq is added. Mutants of Tetrahymena that are unable to divide at the restrictive temperature, but which continue macromolecular synthesis, were found to be resistant to Hq treatment. Conditions were obtained in which more than a 1,000-fold difference in survival was seen between this class of mutant and the wild type. The effect of Hq on three other classes of temperature-sensitive mutants was examined, and the results are discussed.