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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 7612

Ellen M. Grelland; Growth Control by G2-arrest in Batch Cultures of Tetrahymena vorax. Protistologica XXII(3):245-256, 1986

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In the polymorphous ciliate Tetrahymena vorax, age distribution in microstome populations of different cultures ages has been investigated by recording cell cycle events after resuspension in new medium. With increasing culture age there is progressive increase in a population dividing at 3.5 hours after resuspension. Increase in synchrony continues after the beginning of the stationary phase, to a maximal level of 75% on the division index at a culture age of 168 hours. These results suggest that the T. vorax cell cycle in this system is regulated at a specific rate limiting point in the cell cycle. In stationary cultures the peak of dividers is one hour delayed, suggesting that stationary cells are in a different cycle state from slowly cycling cells. The synchronously dividing population has been found by autoradiography to divide without previous DNA synthesis, and it is therefore a G2 population. Growth is imbalanced during the microstomes growth cycle. Cell volume in early stationary cultures is 8 times the cell volume in fast exponential cultures. The type of growth imbalance indicates independent regulation mechanisms for mass growth and cell division.