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                        1. Genetic Engineering in Bioremediation
Enhancing bioremediation—the process of using living organisms, usually microorganisms or plants, to cleanse and restore contaminated environments—is made possible in large part by genetic engineering. Scientists can improve or add particular metabolic pathways to organisms by genetic manipulation, increasing their capacity to degrade contaminants.
Natural microorganisms may not:
- 
Survive in highly toxic environments. 
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Possess metabolic pathways to degrade synthetic or persistent pollutants (e.g., heavy metals, PCBs). 
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Act fast enough to clean up spills or contamination. 
Genetic engineering addresses these limitations by modifying or enhancing the microbes’ capabilities.
Examples of Engineered Organisms
| Organism | Pollutant | Genetic Modification | Outcome | 
|---|---|---|---|
| Pseudomonas putida | Toluene, benzene | Engineered with toluene dioxygenase | Efficient aromatic hydrocarbon degradation | 
| Deinococcus radiodurans | Radioactive waste | Introduced genes for heavy metal uptake | Survives radiation and accumulates metals | 
| Escherichia coli | Mercury | Mer operon for mercury resistance | Converts toxic Hg²⁺ to less toxic Hg⁰ | 
| Transgenic plants (e.g., Indian mustard) | Heavy metals (Pb, Cd) | Metal transporter genes from bacteria | Phytoextraction of metals from soil |