Euglena Gracilis Experiment

Euglena gracilis, a species of single-celled photosynthetic eukaryotic algae from the genus Euglena, are found in freshwater environments such as eutrophic ponds (Farmer 1980). A key characteristic of E. gracilis are their two flagella, one of which is used for locomotion. These eukaryotic algae undergo cell division asexually in the dark (Farmer 1980). A study done by Professor Michael A. Sleigh of the Department of Biology at the University of Southampton, England shows that E. gracilis grow at the optimal temperature between 5 to 35 degrees Celsius. Professor Petersen-Mahrt Svend of SEMM The European School of Molecular Medicine states that E. gracilis has a high sensitivity to environmental changes such as the change in pH levels (Petersen-Mahrt 1997). The pH level [of the environment] can directly distress the absorption of nutrients in marine environments. E. gracilis has been found to endure an expansive range [compared to] other algae (Danilov and Ekelund 2001).

Through studies done by William J. Robbins, a botanist from Columbia University, E. gracilis has been found to grow best at a pH level of 3.0

gracilis population growth between the range observed by the previously mentioned studies. We intend to study how the external pH levels affect E. gracilis’ growth rate by altering the pH levels of their environment. Because of the varying results of these multiple studies, our question is, out of three experimental groups, which pH level yields the closest optimal external pH for population growth in Euglena gracilis? We hypothesize that E. gracilis will have optimal population growth at a pH level of 7.0 due to the fact that the organism’s natural environment, freshwater, has an average natural pH level of 7.0. The previous results of Danilov and Ekelund’s experiment attest to our hypothesis because the E. gracilis cultures grown in a pH of 7.0 had the best growth