The Effect of Caffeine on the Swimming Speed of Tetrahymena thermophila

Abstract

Caffeine is a prevalent chemical that is often found in ecosystems. Previous research has shown that high concentration of caffeine has a negative impact on the growth and survival of protists. The objective of this experiment is to determine the effect of caffeine on the swimming speed of T. thermophila, a unicellular microorganism found in freshwater environments. We predict that higher caffeine concentrations will lead to decreased swimming speeds of T. thermophila. To test this prediction, we incubated T. thermophila in solutions of 0 μM, 10 μM, 100 μM, or 1000 μM of caffeine for 10 minutes and observed their movement under a dissecting microscope. Cell movement was recorded and average swimming speeds were determined. Our results show there is no significant difference in the swimming speed of T. thermophila between the different caffeine treatment groups, thus we fail to reject the null hypothesis that caffeine concentration has no effect on the swimming speed of T. thermophila. However, the cells exposed to the highest caffeine concentration had the highest swimming speeds, at 1.5 times faster than those in the control group, and T. thermophila exposed to the medium caffeine concentration had the lowest swimming speed. This study allows us to further understand the impact of chemicals upon the microbe community.