Ansamitocin-induced synchrony in Tetrahymena pyriformis

Ansamitocins inhibited cell division in Tetrahymena pyriformis W at low concentrations and caused cells to become more rounded. Exposure to ansamitocins for 5 h or more resulted in a burst of synchronous division at 100 min after removal of the antibiotics with a maximum division index of 70%. A second burst of synchronous division occurred 300 min after removal with a peak division index of 55%. The rounding of the cell shape was restored by the completion of the first division. When RNA or protein synthesis was blocked by chromomycin A3 or cycloheximide, the first division was suppressed. When DNA synthesis was blocked by methotrexate plus uridine, synchronous division still occurred; furthermore, the DNA content of T. pyriformis cells did not increase before the first division. These findings suggests that the first synchronous division requires RNA and protein synthesis but does not require DNA synthesis. Interference by ansamitocins with the fuction of microtubule systems in T. pyriformis is discussed.