Maintaining Clonal Paramecium tetraurelia Cell Lines of Controlled Age through Daily Reisolation

INTRODUCTION The sexual cycle of Paramecium tetraurelia can be managed by controlling food uptake, allowing the study of developmentally regulated differentiation in synchronous cultures. Clonal cell lines can be established easily by single cell isolation and can be grown in bacterized grass infusion medium for a large number of vegetative divisions before entering senescence. Sexual reproduction is triggered by starvation and therefore can be induced or prevented as needed by controlling the availability of food. Given a constant supply of food, P. tetraurelia cells will remain in the vegetative phase of their life cycle and, at 27°C, will divide by binary fission every 6 h. The daily reisolation procedure described here results in populations of P. tetraurelia of known age and produced under reproducible physiological conditions, which can help to standardize experiments. Paramecia produced under these conditions are suitable for immunocytochemical studies or use in genetic cross experiments.