Dual Capacity for Nutrient Uptake in Tetrahymena. II. Role of the Two Systems in Vitamin Uptake

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Abstract
A mutant strain of T. pyriformis without food vacuoles failed to grow unless the nutrient media were richly supplemented with vitamins and trace metals. Calcium folinate alone can replace the extra vitamin supplementation. The mutant requires .apprx. 90-fold higher concentration of folinate than the wild-type cells to give similar growth responses in a chemically defined medium. The food vacuole is an important route of uptake for this vitamin in the wild-type cells. No difference between mutant and wild-type cells in their requirements for nicotinic acid, pantothenic acid, riboflavin-monophosphate, and pyridoxal; an extravacuolar route probably contributes importantly to uptake of these 4 compounds.