Problem 7 - Campbell Biology

Question

Which of the following would be considered an example of bioremediation? \begin{equation} \begin{array}{l}{\text { (A) adding nitrogen-fixing microorganisms to a degraded }} \\ {\text { ecosystem to increase nitrogen availability }} \\\ {\text { (B) using a bulldozer to regrade a strip mine }} \\ {\text { (C) reconfiguring the channel of a river }} \\ {\text { (D) adding seeds of a chromium-accumulating plant to soil }} \\ {\text { contaminated by chromium }}\end{array}\end{equation}

Step-by-Step Solution

Answer

(A) and (D)

Step 1: Understanding Bioremediation

Bioremediation is the process of using living organisms to remove or neutralize contaminants from a polluted area, such as soil or water. This typically involves microorganisms or plants that can detoxify pollutants through natural biological activity.

Step 2: Analyze Option (A)

Option (A) suggests adding nitrogen-fixing microorganisms to a degraded ecosystem. Nitrogen-fixing microorganisms convert atmospheric nitrogen into a form that plants can use, thereby improving nitrogen availability in the soil. This involves the use of living organisms to improve soil health, fitting the definition of bioremediation.

Step 3: Analyze Option (B)

Option (B) involves using a bulldozer to regrade a strip mine. This is a mechanical action and does not involve the use of living organisms. Therefore, this option does not qualify as bioremediation.

Step 4: Analyze Option (C)

Option (C) involves reconfiguring the channel of a river. Similar to Option (B), this is a physical alteration of the environment and does not use living organisms. Hence, this also does not fit the definition of bioremediation.

Step 5: Analyze Option (D)

Option (D) suggests adding seeds of a chromium-accumulating plant to soil contaminated by chromium. This involves using plants to absorb and accumulate the chromium from the soil, thereby detoxifying it through natural biological processes. This fits the definition of bioremediation.

Step 6: Conclusion

Based on the analysis, Options (A) and (D) involve the use of living organisms to remove or neutralize contaminants, so they are examples of bioremediation.

Key Concepts

Nitrogen-Fixing Microorganisms

Nitrogen-fixing microorganisms play a vital role in bioremediation. These organisms have the unique ability to convert atmospheric nitrogen into ammonia, which can then be used by plants. This process is called nitrogen fixation. Without these microorganisms, most plants would not have enough nitrogen available to grow.
There are numerous types of nitrogen-fixing bacteria, such as Rhizobium, which form symbiotic relationships with legumes. They live in root nodules and directly provide nitrogen to the plant.
Another group are free-living nitrogen fixers like Azotobacter. By adding these microorganisms to degraded ecosystems, the soil's nitrogen levels are replenished, promoting plant growth and helping to restore the environment.
This is a clear example of bioremediation as it uses living organisms to improve soil health.

Contaminant Detoxification

Bioremediation often involves the detoxification of contaminants from polluted environments, making them less harmful or completely neutralized. For instance, many microorganisms have the ability to break down pollutants like oil spills, pesticides, and heavy metals through metabolic processes.
In the case of oil spills, bacteria such as Alcanivorax can metabolize hydrocarbons, which are the main components of oil. This biological activity turns the harmful oil into harmless end products like water and carbon dioxide.
Moreover, some fungi can decompose synthetic pollutants. For instance, the white-rot fungus Phanerochaete chrysosporium can break down a wide variety of toxic chemicals. This ability makes them valuable in cleaning up contaminated environments.
By utilizing such biological methods, the harmful impacts of pollutants can be significantly reduced, showcasing the efficiency of bioremediation techniques.

Chromium-Accumulating Plants

Certain plants have the remarkable ability to accumulate and detoxify heavy metals from contaminated soils. These plants are known as hyperaccumulators. One prominent example is chromium-accumulating plants, which can absorb and store chromium within their tissues.
Chromium is a heavy metal that can be toxic to both plants and animals at high concentrations. However, plants like Brassica juncea (Indian mustard) can endure and accumulate high levels of chromium. Through the process of phytoextraction, these plants take up chromium from the soil, storing it in their shoots and leaves.
Once the plants have grown, they can be harvested and safely disposed of, effectively removing the chromium from the soil. This natural and cost-effective method highlights the potential of using plants for bioremediation of heavy metal contaminated sites.
This technique offers an eco-friendly solution to soil pollution, promoting healthier and cleaner environments.