Phagocytosis of Tetrahymena is considered. Rate of vacuole formation depending on the time of exposure of the organisms to the India ink solution is researched. Initial hypothesis stated that in the course of time, more vacuoles are formed. The hypothesis was confirmed experimentally. Directions for further research are considered.
Tetrahymena is a unicellular protozoan living in fresh water. These species are common in aquatic habitats, and are well-known for growing in high density (Atlas and Parks, p.170). These organisms are frequently used for studying basic biological mechanisms and factors affecting them. The purpose of this research is to investigate the effect of India ink on phagocytosis, in particular to analyze the impact of time during which the organisms are exposed to India ink on the process of vacuole formation. The hypothesis is that the longer Tetrahymena organisms are exposed to the India ink solution, the more vacuoles will be found inside cells.
Materials and methods
Materials for the experiment include Tetrahymena grown in 2% proteose peptone for 48 hours; 1% India ink solution, culture tubes, compound microscope, glutaraldehyde.
Method of researching phagocytosis in Tetrahymena consisted of the following steps:
1) 5 ml of Tetrahymena and 5 ml of 1% India ink solution were mixed and placed in the test tube
2) Sample cells at 0, 2, 5, 10, 20 and 30 minutes after the start of the experiment were taken
3) Every sample was placed in 3% glutaraldehyde for fixation (cells were killed by glutaraldehyde) (Bozzone, p. 137)
4) Each sample was observed using the microscope at 100-200X magnification
5) For any 25 cells from every sample, number of vacuoles inside each cell was calculated
6) Mean number of vacuoles per cell was calculated for each sample
Table 1 shows the results of the experiment:
Time after feeding (min) Mean number of vacuoles per cell
Table 1. Effect of India ink on phagocytosis of Tetrahymena
Figure 1 shows the dynamics of vacuole formation depending on the time passed after the start of the experiment.
Figure 1. Dynamics of vacuole formation
It is possible to see that the longer Tetrahymena stay in the India ink solution, the more vacuoles are produced in the cells. Thus, the hypothesis was confirmed. For further research of phagocytosis, it would be appropriate to study the effect of different India ink concentrations on the speed of vacuole formation. Also, it would be appropriate to test the hypothesis on several culture tubes with Tetrahymena, and to compare starved Tetrahymena reactions to well-fed ones (Wheatley and Rasmussen and Tiedtke, p. 371). Other factors that might change the rate of vacuole formation are temperature, choice of food, exposure to light etc.
Atlas, R.M. and Lawrence C. Parks. Microorganisms in our world. Mosby, 1995.
Bozzone, D.M. Investigating Phagocytosis in Tetrahymena. The American Biology Teacher, 2:62, 136-139, 2000.
Wheatley, D. N., L. Rasmussen, and A. Tiedtke. Tetrahymena: A model for growth, cell cycle and nutritional studies with biotechnological potential. BioEssays 16:5367-371, 1994.