“The McMurdo Dry Valleys in Antarctica are the closest terrestrial analog we have to what’s happening on other planets,” says David Goerlitz, director of operations for the Genomics and Epigenomics Shared Resource at Georgetown University Medical Center. “It can inform our life detection strategies for other worlds.”
Goerlitz is part of a Georgetown research team that traveled to McMurdo Station, a research center in Antarctica operated by the National Science Foundation, to test theories of long-term cell survival in microbes using next-generation DNA sequencing. They were the first to bring DNA sequencing to the seventh continent.
Before they were allowed off McMurdo Station, the team underwent three days of extensive survival training. “One of the things we learned from our survival instructors is the adage ‘You’re not dead until you’re warm and dead.’ If something happened and a team member became unresponsive, it’s important to know that when a body is exceptionally cold it can appear lifeless, because respiration and brain activity is so slow. But the person can still be warmed up and revived,” Goerlitz explains.
This same concept drove the team’s hypothesis about the microbes they were in Antarctica to study.
The McMurdo Dry Valleys are home to many frozen lakes and ponds that result from glacial melt. “They are extremely cold, extremely dry environments. The lakes are mostly frozen year-round and they’re incredibly salty,” Goerlitz notes. “But despite all of that, there are ecosystems of microbial extremophiles that have evolved and adapted to survive in these environments.”
In 2002 a research team uncovered 2,800-year-old microbes preserved in the ice. “They exposed them to liquid water in the lab and they reanimated,” he explains. “If the ancient cells we have collected are dead, then their DNA would have been exposed to the elements and would be highly fragmented. But if they are alive, their DNA would be tucked safely away in a hibernating cell.”
The longest DNA sequence collected from a dead cell is 1,000 base pairs long. The Georgetown team’s preliminary data demonstrates that they collected sequenced DNA over 68,000 base pairs long from 10,000 year-old microbial samples, meaning that the DNA came from viable cells.
Goerlitz sees great potential for the research.
“If these microbes can survive here,” he says, “then it really stretches our understanding of what is a habitable environment.”