The Effect of Various Dissolved Oxygen Levels on the Growth and Population of Escherichia Coli
The purpose of this experiment was to find the effect of dissolved oxygen levels on the growth and population of Escherichia coli. Five separate five-gallon buckets filled with four gallons of water had dissolved oxygen pumped into them, each having differing amounts of dissolved oxygen (6.6, 7.0, 7.4, 7.8, 8.2 mg/L). After letting the water dechlorinate, and covering it for two days, a sample of E. coli was added into each bucket of water. Three readings were taken over a five day period, on day 1, day 2, and day 5, with days 3 and 4 occurring over the weekend. Since E. coli uses oxygen in respiration and cell growth, it was predicted that the water bucket with the highest amount of supplied dissolved oxygen (8.2 mg/L) would have the largest population of E. coli after five days of exposure to the designated oxygen treatment which was determined by the change in dissolved oxygen over the five day period.
The original hypothesis was accepted; however, both the high (7.8 mg/L) and the highest (8.2 mg/L) yielded the same highest average change of 0.88 mg/L. These results do follow previous research and studies conducted. This information could be helpful to the teams of scientists who study bacteria in lakes, and the researchers who take water quality tests. False readings are taken for water quality because the water samples are taken from dead zones, or zones of the water with little to no dissolved oxygen (also known as anoxia or hypoxia respectively). Since these false testings allow the bacteria and pollution levels in the lakes to be much too high, it can result in illness or even death in humans, pets, and wildlife.
Research Conducted By:
Skyler Flake
Warren Mott High School
Trudy Shrum
South Lake High School
Warren Consolidated Schools