Humans cause large–scale pollution that is difficult to clean up.

Bioremediation is a process that uses organisms and microorganisms to break down pollutants.

Microorganisms work best to break down pollutants under specific conditions.

Microorganisms can be engineered for a particular function.

• Bioremediation – the use of either naturally occurring or deliberately introduced microorganisms or other forms of life to consume and break down environmental pollutants, in order to clean up a polluted site.
• Microorganism – a microscopic organism, also known as a microbe.
• Pollutant – a substance that harms the environment•
• Hydrophobic – to repel or not mix with water

Bioremediation Data Table

Bioremediation Worksheet

What you need:

− Several small beakers/containers (9 per group; ask SEP)

− For optimum pH setup:

o Vinegar (more info below)

o Strong window or bathroom cleaner (more info below)

o pH paper/test strips

− For op0mum nutrient setup:

o Sugar or glucose

− For optimum temperature setup:

o Refrigerator

o Incubator (ask SEP)

− For optimum salinity setup:

o Salt

− Corn oil (or other food oil like vegetable, olive, or peanut oil)

− Rid-X Septic System Treatment powder (can purchase from grocery store)

− Tetrazolium indicator, 0.02% (Carolina, item #896930 for 5 g)

− Gloves

− Optional:

o Trays

o Cheese cloth

Groups of 3-4 students

Students should know about density (of oil versus water), oil’s hydrophobic properties, and it may be helpful for them to also know the general chemical structure of oils and relate that to its hydrophobic properties. It might also be helpful for students to brainstorm why oil spills area particularly difficult form of pollution to address and other methods to clean up oil spills.

Depending on which experimental conditions students investigate, it would also be beneficial for students to understand the basics of acids and bases (e.g., be familiar with pH).

• Understand that microbes can be engineered to digest oils and other chemicals that can’t be broken down by other methods.•
• Understand that different environmental conditions will impact the rate and degree of oil degradation.
• Develop students’ ability to collect evidence through observation.

One way humans pollute the environment is through oil spills. Oil spills are particularly tricky to clean up because they happen on a large scale, the oil disperses quickly, and they significantly impact the surrounding ecosystem. One way that oil spills are cleaned up is using naturally occurring microbes that break down the oil into non–toxic components. This process is called bioremediation. However, naturally occurring microbes work very slowly, so scientists have engineered oil eating microbes that work faster. The Rid–X powder used in this experiment contains engineered microbes that are good at cleaning up septic systems, but here they are used to clean up oil.Engineered microbes often have special properties built in to make sure they do what they were made to do. This includes things like “kill switches” to ensure the microbes don’t stay in the environment permanently.

Engineered microbes can be used in a variety of applications(including the food industry, environmental protection efforts, and disease management) that require unique properties suited for that application. More info: What is Bioremediation?

Vinegar acts as an acid to lower the pH of the water, while the window/bathroom cleaner acts as a base to increase the pH of the water. It takes about 12 drops of vinegar to decrease the pH to 5.0; depending on the brand of cleaner you use, the number of drops to add will vary. Test frequently to monitor how the pH changes as you add the chemicals.

Some of the materials (bathroom cleaner, tetrazolium indicator, and Rid–X) used in this lesson are quite harmful. Make sure to be very cautious and wear gloves when handling these materials. Take extra care not to inhale the chemicals. The tetrazolium indicator is a chemical that turns pink when organisms are metabolizing carbon compounds (like oil). In this lab, the tetrazolium indicator shows us which conditions the bacteria are most active in.

Day 1:
Introduction (15 mins):
Ask students if they’ve ever heard of an oil spill. Have volunteers share a definition and/or ways that oil spills are cleaned up. Introduce the idea that microorganisms, like bacteria, can also be used to clean up pollutants like oil in a process known as bioremediation (the video from the content background section can be used to supplement this). Key things to emphasize are that there are naturally occurring bacteria that can break down oil, but this is a very slow process which makes it hard to clean up large oil spills.

However, scientists have engineered (or modified) bacteria to be extra-good at cleaning up oil spills by working faster and breaking down oil in larger quantities. Tell students that they’re taking on the role of scientists who have been tasked with cleaning up a hypothetical oil spill in a body of water near them using newly engineered bacteria. They have to test which conditions will help bacteria break down the most oil.
Then introduce the 5 experimental conditions: best temperature, best pH, the effect of adding nutrients, and the number of microbes needed. Have groups choose a condition (draw from a hat or sticks, randomly assign, etc.) and read the procedure on the student handout before preparing their materials.

Setting up the beakers (45 mins):
Encourage students to follow the student handout. Groups should label their beakers/containers according to the handout before adding anything. Students should wear gloves and be extra careful around the Rid-X.
Once the beakers are set up, have students make observations, take pictures of the beakers, and add them to a google slides presentation for comparisons later in the week. When they’re done, they can place their beakers onto a tray for easy transportation and move them to the
back of the room. They should be left at room temperature and uncovered overnight. Have students make observations again 4 – 6 hours later, and every subsequent day.

Day 5:
Observations (10 mins):
Have students record and discuss observations with their group, and also take pictures to upload to the google slides presentation.

Wrap-up/Closure (10 mins):
Give groups a ½ sheet of poster paper and have them brainstorm other uses for engineered bacteria: Where might they be helpful? What would the bacteria do? Would they need special instructions, like a kill switch?

After setting up their beakers, have students predict what will happen and why. Encourage them to consider the role of the water/oil control.
You can also have students discuss how this experiment is applicable to the real world: How could this help in an oil spill? What are pros and cons to this method? How do we make sure the microbes don’t get out of control? Are there other things we could use engineered microbes for?

This activity is closely related to the bioremediation final challenge (see more here). Students can replicate bioremediation using this final challenge prompt.

Groups can also make a poster that (1) summarizes their findings/observations and (2) proposes an engineered microbe to solve a real-world problem. Examples include food shortages, restoring soil quality, managing diseases, landfills, and more. If students are having trouble thinking of an application for engineered microbes, it might be helpful to have a class share-out about ideas. For their proposed engineered microbes, they should include:

• The problem the microbe will solve
• The environmental conditions the microbe will experience
• How to keep the microbe under control

Reflection:
This activity can also be adapted for other types of pollution that may be more relevant to
students’ lives. For example, if students live in an agricultural area, soil contamination that is
cleaned up by phytoremediation could be used instead.

Interdependent Relationships in Ecosystems
ETS1 Engineering Design

HS-LS2-7 Ecosystems: Interactions, Energy, and Dynamics
(Students design an experiment to see which conditions are most favorable for oil eating
microbes to clean up a hypothetical oil spill caused by humans.)

LS2.C Ecosystem Dynamics, Functioning, and Resilience

LS4.D Biodiversity and Humans

ETS1.B Developing Possible Solutions

Practice 6. Constructing Explanations and Designing Solutions

Stability and Change