Question 19 from UPSC CSE 2017 - Environment

Question

In the context of solving pollution problems, what is/are the advantage/advantages of bioremediation technique?
1. It is a technique for cleaning up pollution by enhancing the same biodegradation process that occurs in nature.
2. Any contaminant with heavy metals such as cadmium and lead can be readily and completely treated by bioremediation using microorganisms.
3. Genetic engineering can be used to create microorganisms specifically designed for bioremediation.
Select the correct answer using the code given below:

Accepted Answer

Correct Option: C. 1 and 3 only

Strategy: Your primary focus should be on Statement 2. Notice the extreme keywords: 'any', 'readily', and 'completely'. Science-based statements with such absolute claims are often incorrect. Heavy metals are elements; they cannot be completely broken down or biodegraded like organic compounds. They can only be transformed or sequestered. This makes Statement 2 false. Eliminating options containing Statement 2 (B and D) leaves you with A and C. Statement 1 is a standard definition of bioremediation, which is correct. Statement 3 mentions using genetic engineering to create specialized microorganisms, which is a known and logical application in biotechnology. Thus, both 1 and 3 are correct.

Key Info: ## Bioremediation
Bioremediation is a waste management technique that uses naturally occurring organisms like bacteria, fungi, yeast, and plants to break down or neutralize hazardous substances into less toxic or non-toxic forms. It essentially enhances natural biodegradation processes.

*   **Mechanism:** Microorganisms use the contaminants as a source of food and energy, converting them into water, carbon dioxide, and other harmless byproducts.
*   **Types:**
    *   **In-situ:** Treatment of contaminated material at the site itself (e.g., bioventing, biosparging).
    *   **Ex-situ:** Removal of contaminated material to be treated elsewhere (e.g., landfarming, composting, bioreactors).
*   **Advantages:** It is a cost-effective and eco-friendly alternative to traditional physical and chemical treatment methods. It can often be carried out on-site, reducing the need for transportation and disposal of contaminated material.

## Bioremediation of Heavy Metals
Statement 2 is incorrect because heavy metals like cadmium (Cd), lead (Pb), mercury (Hg), and arsenic (As) are elements and cannot be biodegraded or destroyed. Microorganisms cannot 'completely treat' them in the way they break down organic compounds.

*   **Actual Processes:** Instead of degradation, microorganisms can alter the chemical state of heavy metals through processes like:
    *   **Bioaccumulation:** Accumulating metals inside their cells.
    *   **Biosorption:** Binding of metals to the cell surface.
    *   **Biotransformation:** Changing the metal's oxidation state, which can reduce its toxicity or mobility (e.g., converting highly toxic Cr(VI) to the less toxic Cr(III)).
*   **Limitations:** The process is neither 'ready' nor 'complete'. It helps in immobilizing or sequestering the metals, but does not eliminate them from the environment. The effectiveness varies greatly depending on the metal, the organism, and environmental conditions.

## Genetic Engineering in Bioremediation
Statement 3 is correct. Genetic engineering plays a crucial role in enhancing the efficiency of bioremediation. Scientists can modify microorganisms to give them specialized capabilities for degrading specific, persistent pollutants.

*   **Method:** This involves introducing new genes or altering existing ones to create new metabolic pathways that can target stubborn contaminants like chlorinated solvents, pesticides, and hydrocarbons.
*   **Example:** A landmark example is the development of a genetically engineered strain of *Pseudomonas putida* by scientist Ananda Mohan Chakrabarty. This 'superbug' was capable of breaking down multiple components of crude oil, making it highly effective for cleaning up oil spills. This work was central to the landmark U.S. Supreme Court case *Diamond v. Chakrabarty* (1980), which ruled that genetically modified organisms could be patented.

Answer

Option A: 1 only

Answer

Option B: 2 and 3 only

Answer

Option D: 1, 2, and 3