Effect of Ultraviolet Light Exposure on Tetrahymena Thermophila Growth Rates

Abstract

As climate change and ozone depletion contribute to increasing ground-level ultraviolet (UV) radiation, organisms must be able to grow in conditions of increasing UV light to have a chance at survival. Our experiment investigated the relationship between the exposure to UV light and the growth rate of Tetrahymena thermophila, a unicellular eukaryote which increases expression of DNA repair enzymes when exposed to UV. We tested the hypothesis that brief UV exposures would have little effect on the growth of T. thermophila, but longer exposures would decrease growth rates by exposing T. thermophila cultures to 254 nm UV light for either 1 minute or 5 minutes. The treatments were then incubated at 30°C and samples were taken from each of the treatments every hour for four hours; additional samples were taken 21 hours and 46 hours after the initial UV exposure. The cells were counted using a hemocytometer and growth rates were calculated for each replicate and treatment. The growth rate of T. thermophila did not differ significantly among the two treatments and the control (p>0.05). The results of this study could be used to inform further research on the growth and survival of microbes under UV exposure.