The effect of temperature on the population size of Tetrahymena thermophila

Abstract

Tetrahymena thermophila is a ciliated protozoan that inhabits freshwater ponds and is commonly used as a model organism (Cassidy-Hanley, 2012). Like all model organisms, the growth medium and temperature are two important factors. Taking that into account, the purpose of our experiment was to determine the optimal temperature for the growth of T. thermophila by observing the relationship between an increase in temperature and population size. To perform this study, we incubated T. thermophila cultures at 11^oC, 17^oC, 30^oC and 40^oC with three replicates per temperature. We collected mean population sizes every 2 hours in a 10-hour period as well as at 24 hours of incubation for further data analysis and observation. After 24 hours of incubation, we found that the mean population size of T. thermophila incubated at 40^oC was significantly larger than the mean population sizes at 11^oC, 17^oC and 30^oC. This result allows us to reject our null hypothesis and provide support for our alternate hypothesis: stating that an increase in temperature increases the population size of T. thermophila and that the optimal temperature resides close to 40^oC.