Growth Rate of Tetrahymena thermophila: Does progressive increases in incubation temperature result in a greater ability for T. thermophilato adapt to temperatures outside literature ranges for tolerance


  • Cameron Carvalho
  • Chesley Chow
  • Jonathan Kraft
  • Morgan Strohan


As a result of climate change, global temperatures are rising which have the potential to notably impact all ecosystems and the future of biodiversity (Bellard et al, 2012). Tetrahymena thermophila is a ciliated protozoan that can be found in freshwater (Cassidy-Hanley, 2012) and is one of the many species that may be impacted by increasing water temperatures. This investigated whether incremental increases in temperature could result in a T. thermophila culture surviving beyond the literatures cut-off of 41oC (Frankel & Nelson, 2001). T. thermophila were incubated at 42oC, 40oC, and 35oC over the course of four days, after the stock solution was initially diluted with SSP growth medium. After 44 hours of incubation, three samples from each temperature were collected and counted every two hours. A total of eight counts were made for each sample to generate a growth curve. Parallel to these controls that were in the same incubation temperature for the entirety of the experiment, a test group was moved step wise into warmer incubators each day with the growth curve collection being taken once the sample was in the 42oC incubator. A two-way ANOVA test was performed, confirming temperature and time had a significant impact on the cell counts . A Tukey-Kramer post-hoc further revealed that the test group that had moved through the temperatures had no significant difference in cell counts from the control at the same temperature. The elevated temperatures were found to have a significantly adverse effect on growth rates and the incremental increase showed to have no significant advantage for the T. thermophila.