Synchrony in Tetrahymena by heat shocks spaced a normal cell generation apart

Abstract

Repetitive synchrony in cultures of Tetrahymena pyriformis, amicronucleate strain GL, grown in proteose peptone, liver extract medium, can be induced and maintained with heat shocks similar to those used in the multi heat-shock procedure of Scherbaum & Zeuthen (34 °C, 1 2h) but separated, not by 30-40 min at 28 °C but, by 155-160 min, which is the duration of a cell generation at constant 28 °C. Synchronous division and replication follow each other normally except that G 2 is extended by the duration of the heat shock. In repetitive synchrony each heat shock is initiated each time the population has essentially passed macronuclear S. At this time only few cells have yet undergone transition to insensitivity to heat in terms of capacity to divide. Thus the shocks are placed in early G 2. The sequence of recovery from a shock, followed by division and replication occurs at constant 28 °C, and this may be essential for good replication synchrony. When shocks are discontinued, free running synchrony decays through three divisions. The intervals between free running divisions are slightly short, and this accounts for setback of free running division number two in the repetitive synchrony, and presumably for synchrony itself. © 1971.