The effect of copper sulfate toxicity on cell growth rate of Tetrahymena thermophila

Abstract

An investigation on the toxicity of copper sulfate (CuSO₄) on the growth rate of the ciliated protozoan, Tetrahymena thermophila was conducted. Previous studies reveal that that the organism has developed a resistance to heavy metal toxicity, with copper sulfate being one of the most common metals T. thermophila encounters. The growth rate after 24 hours has been measured in these studies, but there is little information on the initial response of the cells with heavy metal exposure. This study observed the cell growth within a 12-hour period at 3 hour increments. It involved three treatments of copper sulfate – 0 ppm (control), 1 ppm and 3 ppm, with 4 replicates each treatment. The growth rate of T. thermophila was determined by the cell counts during the growth phase, and the statistical significance of the results was analyzed using the ANOVA test. It was found that at 0 ppm, 1 ppm and 3 ppm, the growth rate was around 350000 cells/mL/hour, 320000 cells/mL/hour, and 140000 cells/mL/hour respectively. The ANOVA test produced a p-value of 0.00074, which indicated a significant difference amongst the three treatments. Further analysis using the 95% confidence intervals between individual treatments showed that there is no significant difference between 0 ppm and 1 ppm copper sulfate treatment; however, the 3 ppm treatment showed a significant difference compared to the 0 and 1 ppm treatments. Based on the statistical results, the null hypothesis was rejected, indicating a decrease in T. thermophila growth rate with an increase in copper sulfate concentrations. Thus, the alternative hypothesis was supported.