Dormant organisms in rock at Yucca a storage wild card

Tuesday, June 2, 1998 | 9:48 a.m.

Microbiologists have discovered bacteria between 3 million and 6 million years old in volcanic rock at Yucca Mountain and the Nevada Test Site.

Some lie dormant deep underground, starved unless water and other nutrients reach them. Then they are revived and even reproduce.

The implications for bacteria activated by water trapped in Yucca Mountain's pores raise questions about whether nuclear waste can be stored there safely. The possibility that these bacteria could chew through carbon-steel canisters containing high-level nuclear waste prompted studies by the U.S. Department of Energy.

Microbiologist Penny Amy of UNLV and her colleagues, including Dana Haldeman, Beth Pitonzo and Sandra Story, retrieved bacteria samples from tunnels at the Test Site and Yucca Mountain. They first dug into the volcanic rock, known as tuff, at Rainier Mesa on the Test Site where underground nuclear weapons were exploded until President George Bush imposed a moratorium in 1992.

Pitonzo, now at the Community College of Southern Nevada, discovered that some bacteria within Yucca Mountain can be revived after exposure to radiation.

As one of Amy's graduate students, Pitonzo grew bacteria cultures in the laboratory after removing the cells from the mountain's rock. Then she zapped them with radiation by exposing them to Cobalt-60, followed by more nutrients and water. They revived.

Ideally, the bacteria will remain dormant when nuclear waste is buried. However, water flowing within the rock could revive them.

While microbes could take hundreds of thousands of years to travel through Yucca Mountain's rock, it might take less than 50 years for them to go through fractures in the rock, Amy said. That's why the DOE is studying the 34 known earthquake faults at Yucca Mountain. The Ghost Dance fault slices through the repository site north to south.

Amy began studying bacteria that survived in inhospitable environments such as deep sea water when she worked at the Marine Biology Labs at Woods Hole, Mass. Her interest in subsurface survival may lead to proving that life can exist on other planets.

Earlier this century, no scientist believed that cells could survive deep beneath the Earth's surface. What microbe could exist in volcanic rock or the ocean's subseabed?

Nobody thought to look deep into the earth for organisms that can create antibiotics and other drugs, control pests, treat sewage and clean up oil spills until the DOE began to hunt for ways to clean up nuclear and toxic wastes.

Work in the 1970s and '80s by the U.S. Environmental Protection Agency and the U.S. Geological Survey helped scientists realize that bacteria could live in water-yielding rock formations.

Frank Wobber, a geologist and manager at the DOE, began the Subsurface Science Program in the early '80s.

DOE scientists have discovered organisms that live 1.7 miles underground and at temperatures of 167 degrees Fahrenheit. They found that when brought into the laboratory to be studied under a microscope, the microbes can eat waste products and can form nutrients for themselves and other bacteria.

As Amy and other scientists search for ways to keep nuclear waste safe inside Yucca Mountain, others study microbes' power to gobble up toxic wastes or clean up dirty water. Scientists plan to design bacteria and other organisms to do the dirty work.

Craig Venter of the Institute for Genomic Research in Rockville, Md., is on the cutting edge of this research.

Some of the microbes on Earth are critically important for recycling nutrients through ecosystems, helping animals digest food and keeping the biosphere healthy in general.

ITALICS Deinococcus radiodurans END ITALICS, a microbe whose genome (the part of the cell that carries DNA) only recently has been sequenced by scientists such as Venter, has the remarkable ability to withstand 1.5 million rads of radiation. That amount is 3,000 times the dose that would kill an average man.

"This thing can take more radiation than the Incredible Hulk," says Venter's colleague, Owen White, who led the Deinococcus project.

A few hours after a dose of radiation blasts the genome apart, it stitches itself together again. By inserting the genes responsible for this type of genetic repair into the genome of another bacterium that naturally gobbles up heavy metals, the microbe could clean up sites where nuclear tests and weapons production have taken place.