Food Vacuole Observations in Tetrahymena PP2

Tetrahymena is a genus of free-living ciliates, a freshwater organism that can inhabit lakes, streams, and ponds and can be found almost everywhere and in a variety of climates. Their main food source is bacteria. Tetrahymena feed by the process of phagocytosis, where is the engulfing of other cells or particles. The membrane of a phagocyte surrounds a cell to be engulfed and then pinches off to create a phagosome inside of itself that contains the engulfed material. The resulting phagosome may be merged with lysosomes to form a phagolysosome for the digestion and release of nutrients for use in other metabolic processes (Phagocytosis Process). Phagocytosis can be quantitated by counting the number of vacuoles that form in a defined time period. Tetrahymena were selected in this experiment to study food vacuole appearance. This was done by taking five samples of cells as follows: one immediately when the India ink was added, one at ten minutes, one at twenty minutes, one at thirty minutes, and one at forty minutes. Samples were taken in small test tubes, and inside a mixture of 100 µL sample of the Tetrahymena and India Ink (which was used to be able to visually observe number of vacuoles formed) and 20 µL of dilute glutaraldehyde to fix the cells was added at each interval of time. After all of the samples were taken, they were studied under a microscope at the 10X objective. The number of marked vacuoles formed for ten different Tetrahymena cells were recorded for each of the time intervals, then graphed using a line graph.