How do microorganisms contribute to environmental remediation through biodegradation?

• A. Microorganisms release toxins that neutralize pollutants.
• B. They metabolize pollutants, breaking them down into less harmful substances and sometimes mineralizing them.
• C. They add oxygen to water to increase temperature.
• D. They physically filter pollutants without chemical change.

Answer: (B)

Biodegradation is the process by which microorganisms use pollutants as food or energy sources, breaking them down through enzymatic reactions into simpler, less harmful substances. Through these metabolic steps, contaminants can be transformed into harmless compounds or fully mineralized to carbon dioxide, water, and inorganic ions. This is the mechanism behind bioremediation: encouraging microbial activity to clean up contaminated soil, water, or wastewater. Factors such as oxygen availability (aerobic vs. anaerobic conditions), nutrients, temperature, pH, moisture, and how accessible the pollutant is to microbes all influence how quickly biodegradation proceeds. For example, oil-degrading bacteria can break down hydrocarbons in spills, aided by enzymes that oxidize the molecules. This approach relies on chemical transformation, not simply toxin release, and not on physical filtration or on raising temperature by adding oxygen alone. So the description that microorganisms metabolize pollutants, turning them into less harmful substances and sometimes mineralizing them, best captures how they contribute to environmental remediation.