Cell multiplication in Tetrahymena cultures after addition of particulate material.

We have studied the effects of adding participate supplements to populations of Tetrahymena pyriformis in 2 % sterile-filtered proteose peptone broth which supports cell multiplication poorly (generation times in excess of 40 h). The tested compounds were: heat-sterilized suspensions of egg albumin, nutritionally inert particles of polystyrene, sulphopropyl and quarternary amino-ethyl substituted dextran (in concentrations of 4, 40 and 400 fig per ml). The particles had approximately the same size, but differed in their electric net charges. Particulate suspensions of 40 fig per ml or more greatly improved cell multiplication rates (generation times about 6 h). It is probable that the effect of the particles is to induce formation of food vacuoles without which cell multiplication and growth is very slow. The contribution of the food vacuole to nutrient uptake in Tetrahymena is discussed.