Deinococcus radiodurans

Bacteria To Clean Up Nuclear Waste Sites: What is it?
The Guinness Book of World Records calls Deinococcus radiodurans the world's toughest species of bacteria. This mighty microbe can survive radiation levels 3,000 times the lethal dose for humans. Now researchers hope to harness this bacteria to clean up nuclear waste sites.

A Problem... and a Solution?
The U.S. government built more than 50,000 nuclear warheads in the past 50 years, creating a huge toxic waste problem. Many military dump sites contain dangerous organic chemicals and toxic metals mixed with radioactive waste. At more than a thousand sites, polluted water is leaking from underground storage tanks and seeping into groundwater. Over 1.7 trillion gallons of groundwater is already contaminated, and the problem is spreading.

Some bacteria can break down organic chemicals and stabilize or neutralize toxic metals. But at nuclear waste sites, radiation levels would quickly kill these beneficial bacteria. By transferring key genes into D. radiodurans, researchers hope that modified bacteria can help clean up nuclear waste sites by breaking down harmful chemicals, converting toxic metals like mercury and cadmium into safer forms, and transforming water-soluble uranium into a solid that will not leak out of waste sites. Modified bacteria could be available in five years, but extensive safety testing will be required before they can be released into the environment.

ENVIRONMENT: Other Species

Pseudomonas putida
Every year, 25,000 people are killed or injured by land mines, which are difficult and dangerous to find. Most mines leak trace amounts of explosives, however, so researchers have modified Pseudomonas putida bacteria to glow in the presence of TNT. In recent field tests (left), the bacteria revealed simulated mines under ultraviolet light. A variant of harmless soil microorganisms, the bacteria could be sprayed by hand or from crop dusters and would die about a week later.

African Clawed Frog, Xenopus laevis

Frogs
Scientists have inserted genes from a jellyfish into Xenopus laevis frog larvae, causing the frogs to produce a protein that glows in ultraviolet light. Additional "promoter" genes would activate the glow genes only in the presence of specific pollutants, making the frogs living pollution detectors. Intended for use only in the laboratory, tadpoles immersed in water samples would glow faintly under a fluorescent microscope to reveal toxins like retinoic acid, which causes deformities in frogs and birth defects in humans.

Potatoes

Potatoes
Potato plants with transplanted jellyfish genes produce a fluorescent protein when the soil becomes too dry. Light-sensitive instruments can detect the faint glow and alert farmers when their fields need watering. A few sentinel plants in a field could prevent overwatering and keep fertilizer from being washed into water supplies. Now in greenhouse tests, the potatoes may be available by 2005. Future modifications could let potatoes also report on nitrate, phosphate and sucrose levels.

Alfalfa
Pigs and chickens produce 30 million tons of manure in the U.S. each year. This waste includes nearly half a million tons of phosphorous, a major pollutant. Now researchers have genetically engineered alfalfa plants to produce the enzyme phytase, which helps animals absorb up to 42% more phosphorous from their food. That means less phosphorous in their manure and fewer expensive phosphorous supplements in their food, potentially benefiting farmers and the environment.

Are There Unintended Consequences?

The Food Chain
Genetically modified crops could affect the environment in unintended ways. For example, caterpillars and butterflies could be poisoned by eating pest-resistant corn—and animals that feed on them could be affected as well. Other indirect effects of GMOs could include a decline in songbird populations. Herbicide-tolerant crops let farmers virtually eliminate weeds from their fields. But weed seeds are an important food source for skylarks and other birds. According to some estimates, the food available to skylarks could be reduced in some areas by 90%.

Unknown Risks
As plants are modified to produce pharmaceuticals and industrial chemicals, foreign substances will enter the ecosystem and the food chain. How will wildlife be affected when birds, insects, mice and worms eat plants that contain drugs and vaccines, or when soil or stomach bacteria encounter these drugs? Lab tests have shown that genes from modified plants can sometimes "jump" directly into the DNA of bacteria, raising concerns that new strains of bacteria and viruses may arise.

The cost of studying the effect of a single product—corn—on just one species—monarch butterflies—could be greater than the U.S. Agriculture Department's entire annual budget for assessing environmental hazards. And even if such tests were required for all modified organisms, their full environmental effects might not show up until years later. So the potential benefits of modified organisms must be weighed against risks that are simply unknown.