Continuous-flow size selection of Tetrahymena pyriformis ST: changes in volume, DNA, RNA and protein during synchronous growth.

The cell cycle of Tetrahymena pyriformis ST was studied using synchronous cultures prepared by continuous-flow size selection. These organisms had cell cycle times (mean values 151 and 186 min in the first and second cycles respectively) similar to but not identical with the mean generation times of exponential cultures from which they were selected (mean value 165 min). The median volume of cells averaged over the duration of the cell cycle in synchronous cultures was similar to that found in exponential cultures. Total cell DNA, RNA and protein doubled during the cell cycle: there was one discrete S phase which occupied 40 to 50% of the cell cycle time during the period between the end of the selection procedure and the first synchronous division. Total cell protein and RNA increased continuously.