Different growth phenotypes of Tetrahymena vorax V(2) microstomes: I: Changed control of cell cycle passage

During weekly propagation of Tetrahymena vorax V(2) microstomes the phenotype of stationary growth state microstomes changed towards higher cell density and smaller cells. Several significantly different stable levels of stationary densities were found within the range 8-25 × 10(4) cells/ml. The specific G 2 growth arrest found in the low stationary density (LD) cultures was absent from the microstomes in the high stationary density (HD) cultures. Cell cycle traverse during balanced exponential growth was similar in LD and HD cultures. Thus, the phenotype change primarily had an effect on regulation of cell cycle passage towards the stationary phase. During the transitions from LD to HD type the cultures were of intermediate phenotype, and intermediate phenotype cells were present.