Scientists have often wondered about species that are unique to Antarctica. But the focus has mainly been on animals, like cute feathery penguins. But CIRES researchers wanted to dig deeper — into the soils — believing tiny microscopic organisms could be unique to the continent, too.
The team, led by postdoctoral researcher Nick Dragone and co-authored by CIRES Fellow and Director of the Center for Microbial Exploration Noah Fierer, recently found evidence that specific microbes in Antarctica's soils are endemic — located on the continent and nowhere else on Earth. The novel results were published today in the Proceedings of the National Academy of Sciences.
"There is a long-standing assumption in microbiology that 'everything is everywhere,'" Dragone said. "Antarctica has often been viewed as a possible exception, and our findings support that idea. Some Antarctic soil microbes appear to be distinct from those found in soils elsewhere around the world."
Unlike animals or plants, microbes can disperse far, moving around the planet in ways other species can't. They may catch an updraft and float into the atmosphere or hitch a ride on an ocean current out to sea. The authors believed searching for endemic microbes in isolated Antarctica, the most extreme environment on Earth, might prove this theory wrong.
"If we do find we're looking for endemic microorganisms, a good place to start is Antarctica, because it's an entire continent that is geographically isolated, " Fierer said. "It also has unique conditions not typically found in other soil environments. Cold is the obvious one, but also super dry; Antarctica is a desert."
To test this hypothesis, the team focused on bacterial strains within the Arthrobacter group because this group is common in soils from Antarctica to Colorado to the tropics. These strains can also be easy to grow in a lab, which was an important step in their research.
"Arthrobacter as a group may be found all over the planet, but when we look closely at individual strains, just like penguins, Antarctica clearly has its own distinctive biological history," said Byron Adams, professor of biology at Brigham Young University and a co-author of the study.
In the new study, the researchers analyzed soil samples from Antarctica and similar cold, dry environments like the Tibetan Plateau, Svalbard in the Arctic, and Chile's Atacama Desert. In total, they tested over 100 Antarctic strains and nearly 500 from other locations worldwide.
Studying soil samples collected from across the Antarctic continent was key to this project. Dragone and Fierer both noted the research was made possible by long-term collaborations among international research teams who have spent decades collecting samples across the continent for various projects.
Dragone and his team approached their research in two steps.
First, they sequenced the genomes of Arthrobacter strains found in the Antarctic soil samples. Then, they compared the genomic traits of those bacteria found in Antarctic samples to those found in soil samples from around the world pulled from publicly available databases. This step provided evidence that the specific bacteria found in the Antarctic soil samples were different, with 90 percent of the strains found in Antarctica found nowhere else on Earth.
"Previously there have been only a few endemic microbes found in very specific environments," Fierer said. "Finding organisms distinct in Antarctica and only found there does suggest there could be some in other locations; whether other microbial groups show these patterns is a good direction to go."
Next, the team used soil samples to grow strains of Arthrobacter in petri dishes in Fierer's lab at CU Boulder. They mimicked Antarctica's harsh environment to see how different strains adapted to conditions, like temperature and dryness. Mostly, they found that the Antarctic strains grew more slowly but were very resilient. This final step proved that, in addition to being endemic, these Arthrobacter strains are uniquely adapted to Antarctica.
The work sets the stage for future research on microbial life in Antarctica.
"We tend to think of biodiversity in terms of penguins, seals, and whales, but this shows that some of Antarctica's most distinctive species are microscopic," Adams said. "Protecting Antarctic biodiversity also means protecting the biological history contained in a handful of soil."
"We already knew that a broad diversity of microbes can survive the inhospitable conditions of Antarctica, Fierer said. "Now we know that some of those microbes are also unique to Antarctica and are uniquely adapted to life on the southern continent."
