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A team led by the 彩民宝典 looking for organisms that eke out a living in some of the most inhospitable soils on Earth has found a hardy few.
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.
鈥淲e haven鈥檛 formally identified or characterized the species,鈥� said Ryan Lynch, a CU-Boulder doctoral student involved in the study.听 鈥淏ut these are very different than anything else that has been cultured. Genetically, they鈥檙e at least 5 percent different than anything else in the DNA database of 2.5 million sequences.鈥�
Life gets little encouragement on the incredibly dry slopes of the tallest volcanoes in the Atacama region, where CU-Boulder Professor Steve Schmidt and his team 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鈥� samples were below detection limits.
Ultraviolet radiation in the high-altitude environment can be twice as intense as in a low-elevation desert, said Schmidt of CU-Boulder鈥檚 ecology and evolutionary biology department. While the researchers were on site, temperatures dropped to 14 degrees Fahrenheit one night and spiked to 133 F the next day.
How the newfound organisms survive under such circumstances remains a mystery. Although Ryan, 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, they couldn鈥檛 find evidence that the microbes were photosynthetic.
Instead, they think the microbes might slowly generate energy by means of chemical reactions that extract energy and carbon from wisps of gases such as carbon monoxide and dimethylsulfide that blow into the desolate mountain area. The process wouldn鈥檛 give the bugs a high-energy yield, Lynch said, but it could be enough as it adds up over time. A paper on the findings has been accepted by the Journal of Geophysical Research-Biogeosciences, published by the American Geophysical Union.
While normal soil has thousands of microbial species 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. 鈥淭o find a community dominated by less than 20 species is pretty amazing for a soil microbiologist,鈥� Schmidt said.
He 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 19,685 feet and which have been ice-free for 48,000 years, the bacterial and fungal ecosystems have not undergone succession to more diverse communities. 听鈥淚t鈥檚 mostly due to the lack of water, we think,鈥� he said. 鈥淲ithout water, you鈥檙e not going to develop a complex community.鈥�
鈥淥verall, there was a good bit lower diversity in the Atacama samples than you would find in most soils, including other mountainous mineral soils,鈥� Lynch said. 听That makes the Atacama microbes very unusual, he added. 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.
Growth on the mountain might be intermittent, Schmidt suggested, especially if soils only have water for a short time after snowfall. In those situations, there could be microbes that grow when it snows, then fall dormant, perhaps for years, before they grow again. High-elevation sites are great places to study simple microbial communities, ecosystems that haven鈥檛 evolved past the very basics of a few bacteria and fungi, Schmidt said. 听
鈥淭here are a lot of areas in the world that haven鈥檛 been studied from a microbial perspective, and this is one of the main ones,鈥� he said. 鈥淲e鈥檙e interested in discovering new forms of life, and describing what those organisms are doing, how they make a living.鈥�
Schmidt鈥檚 lab, along with others, is studying how microorganisms travel from one site to another. One common method of microbe transport is through the air -- they鈥檙e 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 Volc谩n Llullaillaco and Volc谩n Socompa, the high UV radiation and extreme temperatures make the landscape inhospitable to outside microbes. 鈥淭his environment is so restrictive, most of those things that are raining down are killed immediately,鈥� Schmidt said. 鈥淭here鈥檚 a huge environmental filter here that鈥檚 keeping most of these things from growing.鈥�
The next steps for the researchers are laboratory experiments using an incubator that can mimic the extreme temperature fluctuations to better understand how any organism can live in such an unfriendly environment. Studying the microbes and finding out how they can live at such an extreme can help set boundaries for life on Earth, Schmidt said, and tells scientists what life can stand. There鈥檚 a possibility that some of the extremophiles might utilize completely new forms of metabolism, converting energy in a novel way.
Schmidt also is working with astrobiologists to model what past conditions were like 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.
鈥淚f 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,鈥� he said.
Other paper authors included Andrew King of Ecosystem Sciences, CSIRO Black Mountain in Acton, Australia; Mari谩 Far铆as of Laboratorio de Investigaciones Microbiologicas de Lagunas Andinas, Planto Piloto de Procesos Industriales Microbiologicas, CCT, CONICET in Tucuman, Argentina; Preston Sowell of Geomega, an environmental consulting firm in Boulder; and Christian Vitry of Museo de Arqueologia de Alta Montana in Salta, Argentina.
Contact:
Steve Schmidt, 303-492-6248
Steve.Schmidt@colorado.edu
Ryan Lynch, 303-492-6248
rlynch@colorado.edu
Kate Ramsayer, AGU media relations, 202-777-7524
kramsayer@colorado.edu
Jim Scott, CU media relations, 303-492-3114
Jim.Scott@colorado.edu
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A CU-Boulder-led team has discovered some rare, primitive microorganisms on high volcanoes in South America that may be fueled by drifting gases in the region rather than photosynthesis. (Image courtesy University of Colorado)
