On the role of food vacuole formation in the uptake of dissolved nutrients by Tetrahymena

Abstract

1. 1. In sterile filtered 2 % proteose peptone medium, growth of Tetrahymena pyriformis was slow (doubling time: 100 h at 18 °C) and the mean number of food vacuoles per cell was low (less than 1). 2. 2. Addition of indigestible polystyrene beads (approx. 1 μm in diameter) or ferric hydroxide particles to the sterile filtered medium stimulated considerably both formation of food vacuoles and growth rates (doubling time: about 10 h). 3. 3. Addition of nucleosides at high concentration (6 mM) and glucose to the sterile filtered medium also increased growth rates (doubling time: 20 h), but in this case the number of food vacuoles per cell remained low. 4. 4. The organism T. pyriformis is unable to synthesize purines and pyrimidines de novo. The above findings show that in order to multiply rapidly, it must either have these compounds (or a source of them, e.g. the corresponding nucleosides) supplied at relatively high external concentrations, or be able to obtain them from lower external concentrations through formation of food vacuoles. The same appears to hold for other groups of nutrients, e.g. the amino acids.