CHARACTERISTICS OF DIVIDING AND NONDIVIDING TETRAHYMENA CELLS AT DIFFERENT PHYSIOLOGICAL STATES

Eight defined physiological states of Tetrahymena pyriformis are descr ibed. For dividing cells the states comprise: 1. Exponentially growing cells, 2. Cells at late exponential growth phase, 3. Cells kept at a high cell concentration, 4. Cells shifted up or down by change of medi um, temperature or degree of aeration. For non-dividing cells the stat es are: 5. Cells at stationary phase, 6. Cells during starvation, 7. C ells during shift-up after long-term starvation, 8. Cells at self-indu ced hypoxia. The different cellular states are described by one or mor e of the following characteristics: growth rate, volume, swimming spee d, oxygen consumption and by the oxygen saturation and the pH in the m edium. The results show that T. pyriformis grows equally well in prote ose-peptone (PY) medium from 1 cell ml-1 to 10(3) cells ml-1 as from - e.g. - 10(2) to 10(5) cells ml-1. The maximum cell concentration obta ined depends on the medium and the availability of oxygen. At shift-do wn by decrease of temperature the cells grow slower and obtain a consi derable oversize. Single cells tolerate starvation for 12 days. The ce ll volume (electronically determined) decreased from about 7000 mum3 t o about 200 mum3. Long-term starved cells may be upshifted. Thereby gr owth without cell division can be studied until the cell volume approa ches 2100 mum3 which is the minimum volume of division competence. Und er certain conditions cells may grow into self-induced hypoxia leading to growth arrest. These cells will attain an oversize. The swimming s peed at 28-degrees-C of exponentially growing cells is 0.33 to 0.59 mm sec-1 depending on the medium. At lower temperature the swimming spee d is decreased. In PY-medium the values are: 28-degrees-C (0.57), 16-d egrees-C (0.50), 9-degrees-C (0.37). During starvation the swimming sp eed decreases from about 0.6 to about 0.1 mm sec-1 (after 6 days). The oxygen consumption is for state 1 cells: 3.9 mul O2/10(6) cells min-1 (maximal value). The value of hypoxic cultures is 2. 1, for cells kep t at high concentration 0.4, and for starved cells (24 h) 0.2.