"We started thinking of doing it a different way," Rogers said.
Instead of culturing living organisms, they concentrated on sequencing DNA and RNA in the ice. These methods, called metagenomics and metatranscriptomics, produced thousands of sequences at a time that were then analyzed using computers procedures referred to collectively as "Big Data" methods. In contrast, it usually took years to generate enough cultured organisms for a few dozen sequences.
The problem changed from having too few sequences to having too many sequences to analyze, Rogers said. After two years of computer analysis, the final results showed that Lake Vostok contains a diverse set of microbes, as well as some multicellular organisms.
Long before he began using metagenomics and metatranscriptomics to study the ice, Rogers and his team had developed a method to ensure purity. Sections of core ice were immersed in a sodium hypochlorite (bleach) solution, then rinsed three times with sterile water, removing an outer layer. Under strict sterile conditions, the remaining core ice was then melted, filtered and refrozen.
"Using this method, we can assure its reliability almost to 100 percent," Rogers said.
Eventually, the process rendered pellets of nucleic acids containing both DNA and RNA, able to be sequenced.
Rogers said the team erred strongly on the conservative side in reporting its results, including only those sequences of which it could be absolutely certain were from the accretion ice, but there are a multitude of others he feels are probably from the lake, opening the door to additional investigation.
The DNA sequences they produced have been deposited in the National Center for Biotechnology GenBank database, and will be available to other researchers for further study
|Contact: Jen Sobolewski|
Bowling Green State University