The Effect of Temperature and Salinity on the Growth Rate of Tetrahymena thermophila

Abstract

Tetrahymena thermophila are ciliated unicellular eukaryotes that inhabit freshwater
habitats and use the same food supply as salmon species. Its simple cellular structure, ability to
adapt to different environments, and availability of genetic information make it an ideal organism
for studying a wide range of biological phenomena. T. thermophila feed on bacteria which in turn
are eaten by zooplankton, a primary food source to salmon species. The objective of our study was
to determine the effects of temperature and sodium chloride (NaCl) on T. thermophila while
keeping these interactions in mind. There is a global increase in temperature and freshwater salt
content driven by human activities over the years. This study measured the growth rate of T.
thermophila in 0mM and 50mM of NaCl that were incubated at 25°C and 35°C. For each
temperature and salinity treatment, there were three replicates. Cell counts were taken at 0, 3, 6,
22.5, 25, 30 hours after incubation and cell concentrations were calculated from those counts. The
results of this experiment showed that in the 0mM salinity treatments, the growth rate of T.
thermophila increased from 25°C to 35°C. For the 50mM salinity treatments, the growth rate of T.
thermophila decreased from 25°C to 35°C. Based on a two-way ANOVA, we can infer that
temperature has little to no effect on growth rate of T. thermophila, salinity has a significant effect
on growth rate of T. thermophila, and the interaction between temperature and salinity has a
significant effect on the growth rate of T. thermophila.