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Tomorrow Today

Genetically engineered plants could curtail mercury poisoning

From Correspondent Ann Kellan


A researcher studies the leaves of a 'mercury-eating' plant

A researcher describes the genetic process
Windows Media 28K 56K

CNN's Ann Kellan reports on mercury-eating plants
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Windows Media 28K 56K

ATHENS, Georgia (CNN) -- Researchers at the University of Georgia say they've found a way to restore mercury-contaminated habitats within several years -- a feat that could take Mother Nature thousands of years.

The researchers have genetically engineered plants that can transform toxic mercury to a much weaker, virtually harmless, form known as elemental mercury.

Currently, millions of people worldwide are exposed to dangerously high levels of mercury due to industrial waste.

Mercury poisoning can be found almost anywhere, including places considered remote, like the Amazon River basin in Brazil.

The mercury gets dumped in waste from industrial companies, then ingested by fish. The toxic substance quickly moves its way up the food chain.

But the researchers say their mercury-eating plants could be grown in mercury-polluted environments. The goal would be to rejuvenate the environment and subsequently stop the contamination of the food chain.

"We're very excited," researcher Richard Meagher told CNN. "It's taken years... and now it works! It doesn't just work well, it works spectacularly well." (Audio 256 K/20 sec. AIFF or WAV sound)

How does it work?

The plants absorb mercury through their roots, then release it in a less-toxic form through their leaves  

Mercury found in thermometers or cavity fillings inside your mouth is a much less harmful mercury than that found in industrial waste.

People who have silver mercury fillings are protected naturally from the element's otherwise harmful effects by bacteria that grow inside their stomachs.

The bacteria digests the mercury, breaking it down into a less toxic form.

The same type of bacteria grows in the soil at mercury-polluted sites. Once the mercury is broken down, the less toxic form remains trapped in the soil.

The researchers used genetic engineering to transfer the mercury-eating trait from the bacteria's DNA into plants.

petri dish
Genetically altered seeds are placed in mercury-contaminated soil to see if they will grow  

Their theory was that the altered plants would absorb the mercury through their roots and release the less toxic form through their leaves.

After isolating the mercury-eating genes, the researchers used a high-pressure machine called a gene gun to "shoot" the genes into plant tissue.

"You have to transform a single cell that will divide to grow into a whole tree so that every cell in that tree will be genetically engineered," explained UGA researcher Scott Merkle.

After the plant cells were given the mercury-eating DNA, the plants were left to mature.

Listen to Scott Merkle explain the process of genetically modifying plant cells:

(256 K / 20 sec. audio)

When they matured, the scientists took the seeds from the plants and planted the seeds in mercury-contaminated solutions to see if they would grow. Some did.

Then the scientists measured whether the plants were absorbing and changing the mercury in the soil.

"What these plants are capable of doing is changing the organic mercury all the way to a much lesser toxicity and volatile form of mercury known as elemental mercury," explained researcher Clayton Rugh.

The researchers say 12-year-old poplar trees that were genetically engineered to eat mercury are living proof that the gene can survive for years.

The researchers also say the technique can be used on any plant.

Their project has been so successful that a private company, PhytoWork Inc., has been set up to use the genetically engineered plants to help clean up the environment.

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