Tetrahymena: growth without phagocytosis.

We have succeeded in growing a Tetrahymena mutant without food vacuoles in growth media supplemented with vitamins and heavy-metal salts. This finding implies the existence of adequate alternative routes of entry for every required nutrient, and clearly indicates that the food vacuole in Tetrahymena is a dispensable cellular organelle. The growth of the mutant without food vacuoles makes available a valuable experimental tool.