Student Laboratory Kit
Materials Included In Kit
Motor oil, 30 mL, 1 mL (25 drops) per group
Gravel, coarse, 500 g
Gravel, fine, 500 g
Medicine cups, 60
Oil-eating bacteria, 5 g
Petri dishes, 30
Petri dishes, partitioned, 16
Sand, fine, 500 g
Timothy hay, 20 g
Additional Materials Required
(for each lab group)
Beakers, 1,000-mL, 2*
Erlenmeyer flask, 1,000 mL, 2*
Pond water, 75 mL
Tap water, 2,000 mL*
*for Prelab Preparation
Pond water will produce the best results when conducting this lab. If a pond is nearby, simply collect 75 mL of pond water per group. You will need some type of container; a 2-gallon clean milk jug will work well.
If gathering pond water is not an option, making your own pond water is an excellent alternative. This pond water will be nutrient-rich and support the oil-eating bacteria during the cleaning process.
To prepare the pond water, follow the instructions below at least two days in advance.
- Fill two beakers each with 1,000 mL of tap water and bring to a boil.
- Remove from heat and allow the tap water to cool to room temperature.
- While water is cooling, cut half of the timothy hay (about 10 grams) into small pieces, ½" long, and place into a 1,000-mL Erlenmeyer flask.
- Repeat step 3 with remaining 10 g of timothy hay in a separate 1,000-mL Erlenmeyer flask.
- Pour cooled, boiled water into each Erlenmeyer flask until the hay and water reach 1,000 mL (about 850 mL of water).
- Loosely cover the Erlenmeyer flasks, allowing the mixture to “breathe.”
- Allow the Erlenmeyer flasks to stand undisturbed for 2 days in a warm place, 60–90 °F. When a scum (thin film) forms on the surface of the water, proceed with the oil-eating bacteria preparation.
- Strain the water to remove any hay pieces before distributing to student groups. The procedure should yield 1,500+ mL of pond water. Each group should receive approximately 75 mL.
At least two hours prior to the laboratory work, soak the oil-eating bacteria powder in tap water. Mix 5 g of the bacteria powder mixture in 375 mL of lukewarm water. Stir the mixture occasionally during this incubation period. Dispense 25 mL of the active suspension for each lab group into a plastic medicine cup prior to the laboratory work.
On the day of the experiment, create a control beach for students to compare their results. Fill one chamber of partitioned Petri dish approximately half full with 20–25 g of sand. Place one drop of oil near the outer edge to observe absorption. Then add 3 mL of pond water with pipet to saturate beach material. Place 5 more drops of oil in the center of the sand. Repeat same procedure with fine gravel in chamber 2 and coarse gravel in chamber 3. Cover with lid and place in warm location. You may need to add pond water during the lab to retain moisture.
Although the oil-eating bacteria used in this laboratory are naturally occurring and non-pathogenic, care should be taken when handling the bacteria. Follow all normal laboratory safety procedures. Instruct your students not to touch their face or mouth with their hands when using the bacteria and be sure to wash their work area and hands thoroughly when lab work is completed. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Please review current Safety Data Sheets for additional safety, handling and disposal information.
Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. Follow Flinn Suggested Disposal Method for Type I Biological Materials. This method involves autoclaving or chemical sterilization.
Part I. The Slick
Each day describe the condition of the water and the oil in each Petri dish. Consider textures, colors, consistency and turbidity. Draw sketches if helpful.
Part IIa. The Beach, Control
Part IIb. The Beach, Oil-Eating Bacteria
Answers to Questions
- Why was the “OO” Petri dish used in Part I of this experiment? What purpose did it serve?
The “OO” Petri dish served as a control (i.e., a basis for comparison to see if the oil-eating microbes change the slick in “OEB”).
- Describe the sequence of changes that were shown in the “OEB” Petri dish in Part I. Assuming that these changes illustrate biodegradation, write a working definition of this term.
The oil-eating bacteria mixture clumped the oil slick and the microbes started eating the oil as evidenced by the color changes and the disappearance of the slick. Biodegradation is the breakdown of a non-living substance by a living organism (e.g., oil by bacteria).
- Which beach material seemed to “absorb” oil in a small concentrated area versus allowing it to spread quickly? What problem does absorption in a small area cause the oil-eating bacteria?
The fine sand beach seemed to absorb the oil in one location, minimizing spreading. The problem associated with this type of absorption is the creation of an oxygen-starved environment and the oil-eating bacteria would have a difficult time surviving on this surface.
- Which beach material was the easiest to bioremediate? Explain.
The beach with the most exposed surface area, the coarse gravel beach, would allow the most oxygen to reach the bacteria maximizing the ingestion of oil and bioremediation.
- What evidence would support the claim “the bacteria ingested the oil in the Petri dish”?
Several pieces of evidence collected support the claim that the bacteria ingested the oil. For example, the globs of oil in the oil slick and beach settings only occurred in the experimental Petri dishes. Also, the color changed to show cloudiness and white film near the perimeter and between the pieces of gravel. Finally, over time, the oil around the perimeter became thinner, indicating the oil disappearing.
- What factors might explain the difference in biodegradation on each beach? Remember that the oil-eating bacteria need oxygen as well as oil to thrive and grow.
Each beach allowed biodegradation at some level. The fine sand had the least, most likely due to the lack of oxygen between the fine sand particles. The coarse gravel beach had a fair amount of degradation because of the exposed surface area allowing oxygen to reach the bacteria. The fine gravel also had a noticeable amount of bioremediation, again due to oxygen reaching the bacteria.
- What other uses would oil-eating bacteria have besides cleaning up oil spill disasters? Who else might make use of oil-eating bacteria?
Oil-eating bacteria solutions might be useful in cleaning oil off a garage floor. Service stations that change car oil would find the solution helpful. Any industry that ends up with oil-coated machinery might also find uses for the material.