An Investigative Approach to the Study of Phagocytosis in Tetrahymena

Tetrahymena, a ciliated protozoan, has many attributes that make it an ideal organism for the students ’ study of cells. Tetrahymena can be obtained easily, grow in very simple media, and are readily used to explore ciliary motion, organelle structure and function, cell behaviors, and cell morphology. Because of the ease with which Tetrahymena can be grown and manipulated, they are especially suited for use in inquiry-based labs and student projects. The specific focus of this workshop was to examine the processes of phagocytosis and vacuole formation in Tetrahymena. The effects of several factors on these phenomena were studied. Although the cells we used for this workshop were grown in a bacteria-free medium, Tetrahymena do eat bacteria or other small cells, and organic debris by the process of phagocytosis. When a hungry Tetrahymena encounters food, it uses its cilia to sweep the food into the cell’s oral groove. This process can be visualized by feeding stained yeast cells or India Ink (!; Keenan, 1984) to Tetrahymena. We used the India Ink protocol to study this process. One simply “feeds ” a dilute suspension of India Ink to Tetrahymena, and quantitates the number of black vacuoles, which form in a defined time period. Using this simple procedure, many interesting questions can be addressed regardin