Marine Organisms Living in Extreme Antarctic Conditions Show Complexity, Tenacity of Life

Deep beneath a barren crater in Antarctica, where conditions are so harsh visiting scientists must be trained in survival skills, is Lake Vostok, an ancient subglacial lake that lies far below sea level, formed by a depression created 60 million years ago when the continental plates shifted and cracked.

Lake Vostok, the fourth deepest lake on Earth and the largest of Antarctica's 400 subglacial lakes, has been compared to a lifeless planet in outer space, a place where conditions are extreme, so deep, dark and cold, that no life could exist.

But the sterile sentiments about Lake Vostok may change, as researchers report thousands of microbial species living and reproducing in the extreme environment.

Scott Rogers, a Bowling Green State University professor of biological sciences, and his colleagues made the discovery after analyzing clear-as-diamond ice core samples taken from Vostok.

"We found much more complexity than anyone thought," Rogers said in a statement. "It really shows the tenacity of life, and how organisms can survive in places where a couple dozen years ago we thought nothing could survive."

The ice that covers Vostok is more than two miles thick, built up over the course of millions of years, its composition has long fascinated scientists, who hypothesized that water found in the lake's liquid layer could act as a fossil reserve, sealed off from the environment for eons.

But finding life in the waters may prove more fascinating than any fossilized microbes.

By using a combination of DNA and RNA sequencing of material from the ice samples, the team identified thousands of bacteria, including some commonly found in the digestive systems of fish and other marine life, as well as fungi and two species of archaea - single-celled organisms that tend to live in extreme environments. Other species identified are known from lake or ocean sediments elsewhere. Psychrophiles, or organisms that live in extreme cold, were found, along with heat-loving thermophiles, which suggests the presence of hydrothermal vents deep in the lake.

Rogers contends that the presence of both marine and freshwater species supports the idea that the lake was once connected to the ocean and that the freshwater was deposited in the like by the overriding glacier.

"Many of the species we sequenced are what we would expect to find in a lake," Rogers said. "Most of the organisms appear to be aquatic (freshwater), and many are species that usually live in ocean or lake sediments."

Finding myriad species living in the lake was made possible by the DNA and RNA sequencing, which proved to be more effective than trying slowly culture colonies of bacteria and fungi from ice samples. The sequencing methods, called metagenomics and metatranscriptomics, produced vast amounts of data, upending the scenario for Rogers and his team, who went from having a dearth of information to having more than they could handle. Computer analysis of the genetic data took two years, but the results, Rogers said, are as solid as they are worthwhile.

"The bounds on what is habitable and what is not are changing," he said.

The research is published in the journal PLOS ONE.