Mass selection of conditional mating mutants of Tetrahymena thermophila.

The mating reaction in Tetrahymena thermophila includes a starvation period and two distinct cell interactions, co-stimulation and cell pairing, before the cells are cytoplasmically joined as conjugants. A selection procedure for harvesting mutants unable to mate at a restrictive temperature has been developed. A conjugant pair consisting of one cycloheximide-resistant cell and one wild-type cell (cycloheximide-sensitive) was itself sensitive to the drug. By adding cycloheximide and nutrient medium to a cross made at the restrictive and grow. Repetition of the selection procedure enriched for cells unable to conjugate at the restrictive temperature. The selected cells were able to grow at 38 degrees C and could conjugate at 28 degrees C. This procedure may be narrowed to select specifically for cell interaction mutants.