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MOSCOW, April 29. /TASS /. A team of Russian scientists have studied bacteria of the Antarctic snow to find an answer to the question whether they are adapted to extreme cold conditions or come to the continent from other parts of the world, the Skoltech press service said.
The team led by Skoltech Professor Kostantin Severinov also includes researchers from the Institute of Molecular Genetics (Russian Academy of Sciences), the Institute of Gene Biology (Russian Academy of Sciences), St. Petersburg and Moscow State Universities.
"Our data showed that it’s more likely that bacteria were deposited on the snow surface from the air. Firstly, bacterial content varies from year to year in the same place. Secondly, we didn’t find any bacteria specific for that place. Imagine that every year you visit some natural parks in Africa. You expect to see lions there, not tigers. If you were to see a tiger, it’s likely that someone just brought it there, and you will not see it next year because tigers don’t live in Africa. Well, Antarctic snow bacteria are like tigers, not lions," Konstantin Severinov said.
Samples of snow and melt water collected during two Russian Antarctic expeditions were taken to the laboratory onboard the Akademik Fedorov research ship. The bacteria isolated from these samples were then analyzed in Moscow using modern genomic and bioinformatics methods.
In particular, researchers have studied components of the CRISPR-Cas bacterial adaptive immune systems that protect bacteria from viruses called bacteriophages. During the infection a piece of viral DNA can be integrated into the bacterial genome and make bacteria and its progeny resistant to this particular virus. The genomes of modern bacteria contain various DNA fragments which were captured from phages by ancestral cells.
"Bacteria must be traveling by air because they are very tiny and light. Analysis of their CRISPR-Cas systems showed that these bacteria came from the Southern Hemisphere. Their "medical histories", recorded in the form of acquired viral DNA fragments are very different from those of related bacteria of the North Hemisphere" Severinov said.
The number and variety of Antarctic bacteria is enormous. There are tens of thousands of bacteria in one cubic centimeter of Antarctic snow. Thus, Antarctica should be considered as a huge bacterial storage area, and many of the stored bacteria are still viable. New bacteria are coming all the time, while old ones are sinking deep into the snow. It gives scientists an opportunity to study bacteria from the distant past in the lower snow layers.
This work is a part of a long-term study of Antarctic bacterial community composition. This year scientists will conduct the expedition again, visiting the Vostok station in Antarctica. There is a huge freshwater lake about four kilometers under this station, which may contain special forms of bacterial life.
Results of the work were published in a journal Frontiers in Microbiology.