Freezing and Viability of Tetrahymena pyriformis in Dimethylsulfoxide

Abstract

Ciliated protozoa may be preserved at very low temperatures. Tetrahymena pyriformis, suspended in 10 percent dimethylsulfoxide, survived when frozen in two steps, first to -20 ° C, then transferring immediately to a temperature of -196 ° C. Motility and ability to reproduce were recovered after freezing by this method and subsequent storage for 3 months in a liquid nitrogen refrigerator.