Correlation between cell nutrition, cell size and division control. Part I.

The conventional concept of division control assumes that a certain sequence of biochemical events throughout the cell cycle results in the generation of some specific mitotic trigger. An alternative approach has been examined by us on Tetrahymena pyriformis, namely, that division is started without any specific starter but by deficiency in the cell pool of nutrients. This deficiency, in its turn, is caused by various space disproportions accompanying cell growth.In accordance with the hypothesis under examination, a prompt shift-down in cell nutrition has induced a wave of division in an asynchronous culture of Tetrahymena; a shift-up in nutrition has resulted in delay of division and in a stepwise increase of mean volume of dividing cells.