In a new study published this spring, Colorado State University researchers from the Natural Resource Ecology Laboratory have shown that both bacteria and fungi not only survive, but actively grow in the frozen Arctic tundra – a finding that has significant implications for life on cold planets such as Mars, and for the response of Arctic soils to global climate change.
In recent years, scientists have discovered viable bacteria and other microscopic organisms in some of the most extreme cold environments on earth. In some cases they have been able to isolate some of these microorganisms and grow them under laboratory conditions.
"We know that microorganisms living in permanently frozen environments may have had thousands of years to adapt to those conditions, but what about microorganisms that live in environments that are only frozen for part of the year, such as the Arctic tundra soil? Are these microorganisms able to perform cellular maintenance or grow under frozen conditions?" said Shawna McMahon, co-author of the study and post-doctoral researcher in CSU’s Natural Resource Ecology Laboratory, or NREL.
Since tundra microorganisms experience relative warm conditions in the summer, would they also be adapted to growing in frozen winter conditions or would they simply shut down and wait for soils to thaw in the following spring?
"We were able to definitively show for the first time that both bacteria and fungi are not only surviving the Arctic winter, but some of them are actively growing in the frozen Arctic tundra soil," said Matt Wallenstein, NREL research scientist and co-author.
The implications of this discovery are far-reaching.
"Evidence of frozen water on Mars has fueled speculation that life could have evolved on other planets. However, Mars has been frozen for billions of years. Based on our findings, bacteria and fungi are capable of actively growing below freezing temperatures which suggests that if life did evolve on Mars, bacteria and fungi could have persisted despite frozen conditions," McMahon said.
Beyond the potential of life on Mars, this discovery may help scientist further understand the effects of global climate change on Arctic soils. Some scientists are concerned that global warming may melt permafrost and increase the length of summer in the Arctic. Longer summers may result in the decomposition of currently frozen soil carbon, increasing the release of carbon dioxide into the atmosphere.
"Our results suggest that longer Arctic summers may not be the only important aspect of climate change. Milder winters may also play a role in contributing more carbon dioxide into the atmosphere," said Wallenstein.
McMahon and Wallenstein worked with Josh Schimel from the University of California-Santa Barbara on this study, which was funded by the National Science Foundation. The researchers collected and studied Arctic tundra soil samples from the Toolik Lake region in Alaska.
The study was published in the March issue of Environmental Microbiology Reports.