Scientific treasure, on ice

IN FOCUS

Researchers seek clues to how microbes can survive in the harsh environment of a frigid Antarctic lake

Science

December 05, 2007|By Frank D. Roylance | Frank D. Roylance,SUN REPORTER

It's in one of the most isolated and inhospitable places on Earth - and scientists think it contains one of the most pristine ecosystems on the planet, untouched by millenniums of human activity.

It's called Lake Vostok, and it's the eighth-largest lake in the world, sealed in darkness beneath miles of Antarctic glacial ice. Scientists who have cautiously begun to sample the lake's microbial life say they're opening what they expect will be a "treasure chest of adaptation."

So far, all they've seen are dots in a microscope, probably bacteria, "like little spheres, or little rods, or sometimes like a comma - not a whole lot of shape to them," said Brian Lanoil, the project leader from the University of California, Riverside.

But when DNA analyses get rolling in a few months, scientists hope to learn more precisely what those dots are, and how they've survived being sealed beneath the ice for as long as 1 million years.

Extreme environment

"We want to know how they adapt to live in an environment like that, the most extreme on Earth," Lanoil said. That knowledge might lead to new enzymes for industrial use; clues to how life might have survived on Mars or beneath the surface ice of Europa, a moon of Jupiter; and perhaps new insights into the origins of life on Earth.

Lake Vostok was discovered in 1996 by Russian and British scientists using ice-penetrating radar. Nearly the size of Lake Ontario, its waters are up to 1,300 feet deep and lie beneath 2 1/2 miles of Antarctic ice.

Researchers say they believe the freshwater lake was overrun and "capped" by glaciers 500,000 to 1 million years ago, after the continent drifted south and its climate grew colder.

But thanks to a combination of geothermal heating, the natural insulating properties of the glacier and higher pressure imposed by the weight of the ice on top of it, Vostok has remained liquid at about 27 degrees Fahrenheit.

Whatever life survived those events had to adapt to endure the dark, cold and near-perfect isolation from the rest of life.

"We're real interested to know, under these very stable conditions ... how life has evolved," said Craig Cary, an expert on "extremophiles" on the team and a professor of marine biosciences at the University of Delaware. ("Extremophiles" are microbes that thrive in extreme environments.)

Challenging technology

To find out, scientists must reach down to the lake without contaminating the waters with outside life forms or pollution. It hasn't been easy.

They're using a bore hole drilled by Russian scientists seeking ancient air samples from within the ice cap. To keep their hole open, they filled it with antifreeze - a 60-ton column of kerosene, jet fuel and chlorofluorocarbons.

The 10-year drilling project stopped about 300 feet above the lake's liquid water. In 1998, researchers extracted an ice core, 5 inches in diameter and 11,886 feet long. Most of it is glacial ice - ancient snow, packed tight and filled with pockets of air.

But at the bottom, researchers found "accretionary" ice - lake ice that froze to the bottom of the glacier.

"It's so different from glacial ice," Cary said. "When it first slid out of the bag, everyone just gasped, because it's like this prism of glass ... absolutely perfect ice. It formed under high pressure, so it has no imperfections."

Lanoil described it as "pure, clear, crystalline ice, like diamonds. It's beautiful."

Scientists split the core three ways, with segments going to Russia, France and the United States. The U.S. core went to the National Ice Core Laboratory in Denver, run by the U.S. Geological Survey. It's a repository for ice samples crucial to the study of global climate change.

At Riverside, Lanoil and his team have been working with a segment of lake ice. After decontaminating the surface with bleach, they melted a section and drew off most of the water, leaving "a tiny spot of cells at the bottom of a tube," Lanoil said.

Life is sparse in the lake ice, Lanoil said. "If you go to a normal lake, or the ocean, there's somewhere around a million cells per milliliter." In the Vostok lake ice, "there's somewhere between 10 and a couple hundred cells per milliliter of water," he said. That's not surprising in such an energy-poor environment.

Next, he said, "we break open those cells with enzymes and chemicals ... and purify the DNA."

Scientists will have to "amplify" these tiny DNA samples using cutting-edge techniques for "copying" the genetic material. "Being able to sort and sequence a single cell is right there at the edge," Carey said. "This is really challenging the technology."

Only then can researchers begin to identify the individual organisms, see what they're related to and what genetic changes have allowed them to live in such a hostile, low-energy environment.

Also unknown is whether any of the organisms frozen in the lake ice for hundreds of thousands of years can be revived.

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