June 9th, 2012 by James Ayre
A new DNA analysis of the Martian-like landscape on top of some South American volcanoes has found communities of bacteria, fungi, and archaea. These organisms are not just capable of surviving there, but also deriving their energy in ways not currently known, perhaps from volcanic gases, the researchers think.
“We haven’t formally identified or characterized the species,” said Ryan Lynch, a microbiologist with the University of Colorado in Boulder who is one of the finders of the organisms, “but these are very different than anything else that has been cultured. Genetically, they’re at least 5 percent different than anything else in the [DNA] database of 2.5 million sequences.” The database includes a close-to-comprehensive collection of microbes, and is continually updated as researchers worldwide add to it.
The soil samples were collected on the incredibly dry slopes of the tallest volcanoes in the Atacama region. Whatever snow that does fall there quickly sublimates back into the atmosphere, and the soils there are so depleted that nitrogen levels were below detectable limits. The ultraviolet radiation there is twice as high as even the harshest low-elevation deserts. And the temperature swung from 14 to 133 degrees Fahrenheit in less than 24 hours, during the time that the researchers were there.
How the organisms survive there is a mystery to the researchers. They looked for the genes known to be involved in photosynthesis in the organisms, and looked into the cells looking for chlorophyll, but couldn’t find any evidence that the organisms were photosynthetic.
The researchers think that they might be deriving their energy from the small amounts of carbon monoxide and dimethyl sulfide that are carried to the region by wind.
Normally, in more temperate locations, there are thousands of microbial species represented in just a gram of soil, but in the barren Atacama mountain soils, there appear to only be only a few species that can live there.
“To find a community dominated by less than 20 [species] – that’s pretty amazing for a soil microbiologist,” Schmidt said.
Steven Schmidt, a University of Colorado in Boulder microbiologist, “has studied sites in the Peruvian Andes where, four years after a glacier retreats, there are thriving, diverse microbe communities. But on these volcanoes on the Chile-Argentina border, which rise to altitudes of more than 6,000 meters (19,685 feet) above sea level and which have been ice-free for 48,000 years, the bacterial and fungal ecosystems have not undergone succession to more diverse communities.”
“It’s mostly due to the lack of water, we think,” Schmidt said. “Without water, you’re not going to develop a complex community.”
“Overall, there was a good bit lower diversity [in the Atacama samples] than you would find in most soils, including other mountainous mineral soils,” Lynch said, which makes the Atacama microbes very unusual. They probably adapted to the extremely harsh environment, the researchers propose, or may have evolved in different ways than similar organisms elsewhere due to long-term isolation.
The growth on the mountain might be done intermittently, growing during the short period when there is snow, and then being dormant the rest of the time, maybe even for years. High-elevation sites like this are valued by microbiologists because of their extreme simplicity and presumably “primitive” communal architecture.
“There are a lot of areas in the world that haven’t been studied from a microbial perspective, and this is one of the main ones,” he said. “We’re interested in discovering new forms of life, and describing what those organisms are doing, how they make a living.”
“Schmidt’s lab, along with others, is studying how microorganisms are dispersed — that is, how they travel from one site to another. There’s evidence that one common method of microbe transport is through the air – they’re caught up in winds, sucked up into clouds, form rain droplets, and then fall back to the ground somewhere else as precipitation. But on mountains like Volcán Llullaillaco and Volcán Socompa, the high ultraviolet radiation and extreme temperatures make the landscape inhospitable to outside microbes.”
“This environment is so restrictive, most of those things that are raining down are killed immediately,” Schmidt said. “There’s a huge environmental filter here that’s keeping most of these things from growing.”
The next step for the researchers is to recreate the environment in a laboratory setting and study the microbes there. There is a good chance some of the organisms might use completely new forms of metabolism, deriving their energy in unexpected ways.
The researchers are also working with astrobiologists to try and model past conditions on Mars.
“With their rocky terrain, thin atmosphere, and high radiation, the Atacama volcanoes are some of the most similar places on Earth to the Red Planet.”
“If we know, on Earth, what the outer limits for life were, and they know what the paleoclimates on Mars were like, we may have a better idea of what could have lived there,” he said.
The research has just been accepted for publication in the Journal of Geophysical Research-Biogeosciences.
Source and Images: American Geophysical Union
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