The Effect of Temperature on the Population Health of Tetrahymena thermophila

Abstract

A wide range of studies on Tetrahymena species have been done involving the cell’s cilia and basal body movement, nuclear divisions (both the macronuclear amitotic and micronuclear mitotic divisions), temperature-sensitive mutation and growth response (Pennock et al. 1988). In our study, we incubated Tetrahymena thermophila cultures at 25ºC, 30ºC and 35ºC to investigate the relationship between an increase in temperature and population health. Our group defined population health by analyzing three different factors including: population cell counts, dividing cell counts and cell motility at three different temperatures. We collected data at four different times: after 3, 21, 27 and 39 hours of incubation. Video footage was captured using a Dinoxcope camera and later used to analyze cell motility speeds and quality. Population densities were determined by counting cells through compound microscopes and multiplying counts by their respective dilution factors. After 27 hours of incubation, the mean cell population density incubated at 35°C was significantly larger than the mean cell population density incubated at 25°C. This significant result coincides with the literature and therefore provides evidence supporting the alternative hypothesis stating that increasing the temperature of the environment will increase the population size of T. thermophila. After 39 hours of incubation, a significant difference between the mean speed of cells incubated at 25ºC and those incubated at 35ºC was observed. The cells incubated at 25ºC moved significantly faster than those cells incubated at 35ºC. Considering our population growth and motility results, we conclude that there could be a tradeoff between population growth and motility. At the highest treatment temperature, we observed higher densities of T. thermophila in our replicates and that the cells moved slower than the cells incubated at 25C.