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Bioremediation - Genetically Modified Bioremediators

transgenic organism plasmids biotechnology

Biotechnology can transfer the ability to manufacture detoxifying proteins from one type of organism to another. One organism that was so modified has earned the distinction of being the first micro-organism to be patented. Called the "oil eater," the microorganism was actually a naturally occurring bacterium that had been given four plasmids that were also naturally occurring (plasmids are rings of DNA that can be transferred from one cell to another). It was the combination of the four transferred plasmids in a single bacterial cell that was novel and therefore patent-worthy. The four plasmids in the oil eater gave the bacterium the ability to degrade four components of crude oil. It was invented by Ananda Chakrabarty at General Electric in 1980.

Today, transgenic technology creates designer bioremediators. A transgenic organism contains a gene from another type of organism in all of its cells. The altered organism then manufactures the protein that the transgene encodes. The technology works because all organisms use the same genetic code. In other words, the same DNA and RNA triplets encode the same amino acids in all species.

Transgenic bioremediation can engineer microbial metabolic reactions into plants whose root cells then produce the needed proteins and distribute them in the soil. For example, transgenic yellow poplar trees can thrive in soil that has been heavily contaminated with mercury if they have been given a bacterial gene that encodes the enzyme called mercuric reductase. This enzyme catalyzes the chemical reaction that converts a highly toxic form of mercury in soil to a less toxic gas. The leaves of the tree then emit the gas to the atmosphere, where it dissipates.

Cleaning up munitions dumps is yet another target of transgenic plants, with some interesting biological participants. In one approach, a bacterial gene that breaks down trinitrotoluene (TNT, the major component of dynamite and land mines) is linked to a jellyfish gene that makes the protein glow green. The bacteria can be spread directly on soil that is thought to contain weapons residues, or the genes can be transferred to various types of plants, whose roots then glow when they are near buried explosives. In the future, plants that have been genetically modified in several ways will be able to detect a variety of pollutants or toxins.

Ricki Lewis

Bibliography

Bolin, Frederick. "Leveling Land Mines with Biotechnology." Nature Biotechnology 17 (1999): 732.

Eccles, Harry. Bioremediation. New York: Taylor and Francis, 2001.

Hooker, Brian S., and Rodney S. Skeen. "Transgenic Phytoremediation Blasts onto the Scene." Nature Biotechnology 17 (1999): 428.

Lewis, Ricki. "PCB Dilemma." The Scientist 15 (2001): 1.

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