A new DNA analysis of rocky soils in the martian-like landscape on some volcanoes in South America has revealed a handful of bacteria, fungi, and other rudimentary organisms, called archaea, which seem to have a different way of converting energy than their cousins elsewhere in the world.
“We haven’t formally identified or characterized the species,” said Dr Ryan Lynch, a microbiologist with the University of Colorado in Boulder who is one of the authors of the discovery, “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.”
Life gets little encouragement on the incredibly dry slopes of the tallest volcanoes in the Atacama region, where Lynch’s co-author, University of Colorado microbiologist Dr Steven Schmidt, collected soil samples. Much of the sparse snow that falls on the terrain sublimates back to the atmosphere soon after it hits the ground, and the soil is so depleted of nutrients that nitrogen levels in the scientists’ samples were below detection limits. Ultraviolet radiation in this high-altitude environment can be twice as intense as in a low-elevation desert. And, while the researchers were on site, temperatures dropped to -10 degrees Celsius (14 degrees Fahrenheit) one night, and spiked to 56° C (133° F) the next day.
How the newfound organisms survive under such circumstances remains a mystery. Although Dr Lynch, Dr Schmidt, and their colleagues looked for genes known to be involved in photosynthesis, and peered into the cells using fluorescent techniques to look for chlorophyll, the scientists couldn’t find any evidence that the microbes were photosynthetic.
Instead, they think the microbes might slowly convert energy by means of chemical reactions that extract energy and carbon from wisps of gases such as carbon monoxide and dimethyl sulfide that blow into the desolate mountain area. “The process wouldn’t give the bugs a high energy yield,” Dr Lynch said, “But it could be enough as it adds up over time.”
While normal soil has thousands of microbial species represented in just a gram of soil, and garden soils even more, remarkably few species have made their home in the barren Atacama mountain soil, the new research suggests. The findings will be published in the Journal of Geophysical Research-Biogeosciences.
“To find a community dominated by less than 20 species – that’s pretty amazing for a soil microbiologist,” Dr Schmidt said. “It’s mostly due to the lack of water, we think. 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,” Dr Lynch added. “That makes the Atacama microbes very unusual. They probably had to adapt to the extremely harsh environment, or may have evolved in different directions than similar organisms elsewhere due to long-term geographic isolation.”
Dr 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,” Dr Schmidt said. “There’s a huge environmental filter here that’s keeping most of these things from growing.”
Bibliographic information: Lynch, R. C., A. J. King, M. E. Farías, P. Sowell, C. Vitry, and S. K. Schmidt. 2012. The potential for microbial life in the highest elevation (>6000 m.a.s.l.) mineral soils of the Atacama region. J. Geophys. Res., in press; doi:10.1029/2012JG001961