Extreme extremophiles: in Chile's Atacama Desert (Introduction)

by David Turell , Sunday, August 28, 2022, 14:51 (608 days ago) @ David Turell

Life without oxygen:

https://knowablemagazine.org/article/living-world/2022/treasure-hunt-microbes-chile-ata...

"The famously dry region has long been dismissed as a mostly lifeless wasteland, good for little more than mining of minerals and precious metals. To these researchers, however, it’s a microbial gold mine worthy of protection.

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"Gómez-Silva is part of a small but strong contingency of scientists searching for living microbes here in the world’s oldest desert, a place that’s been dry since the late Jurassic dinosaurs roamed Earth some 150 million years ago. Anything trying to survive here has a host of challenges to contend with beyond the lack of water: intense solar radiation, high concentrations of noxious chemicals and key nutrients in scarce supply. Yet even so, unusual and tiny things do grow, and researchers like Gómez-Silva say that scientists have a lot to learn from them.

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"Without water, little should survive: Cells shrivel, proteins disintegrate and cellular components can’t move about. The atmosphere at the desert’s high altitudes does little to block the sun’s damaging rays. And the lack of flowing water leaves precious metals in place for mining companies, but means distribution of nutrients through the ecosystem is limited, as is the dilution of toxic compounds. Where water bodies do exist in the desert — often in the form of seasonal basins fed by subterranean rivers — they frequently have high concentrations of salts, metals and elements, including arsenic, that are toxic to many cells. Desert plants and animals that manage to make it in the region typically cling to the desert’s outskirts or to scattered fog oases, which are periodically quenched by dense marine fogs called camanchacas.

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"Dorador studies microbial mats that thrive beneath the crust of the Atacama salars, or salt flats, that are sometimes submerged under a layer of brine. A slice through one of these mats yields what might be taken for an alien serving of gelatinous lasagna. Inside the pasta-dish-gone-wrong, which can grow to several centimeters thick and is held together in part by cell-exuded goo, live millions of microorganisms of various types. The species cluster together into distinct, colorful layers: Purple streaks often represent bacteria that can avoid oxygen; bright green stripes might indicate ones that produce it. Other colors hint at cells that can capture nitrogen from their surroundings, produce foul-smelling sulfur, or leak methane or carbon dioxide into the air.

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"They are also a glimpse into the past, as this layered community looks very much like what scientists believe were the earliest ecosystems to come about on Earth. As they grow, some microbial mats form mounds of layered sediment that can be left behind as lithified fossils, called stromatolites. The oldest of these stromatolites date back to 3.7 billion years, when Earth’s atmosphere was devoid of oxygen. Thus, living mats, still found in extreme environments the world over, are of great interest to researchers trying to piece together the puzzle of how life as we know it today came to be. (my bold)

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"Then, on a 2012 trip with Argentinian and Chilean colleagues, Visscher found what he was looking for in a vibrant purple microbial mat thriving below the surface of the Atacama’s La Brava, a hypersaline lake more than 7,500 feet above sea level. Unlike previously studied microbial mats, Visscher couldn’t detect oxygen in the La Brava mats or the waters around them then nor during several subsequent visits at different times of the year. Thus they provide an ideal natural laboratory, he says, and have lent weight to earlier theories about the importance of arsenic for early life.

“'I had been looking for well over 30 years to find the right analog,” he says. “This bright purple microbial mat may have been something that was on Earth very early on — 2.8 to 3 billion years ago.”

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"Other microbes take an active role in seeking out water. In 2020, a group of scientists from the United States described in PNAS a bacterium living within gypsum rocks that secreted a substance to dissolve the minerals around it, releasing individual water molecules sequestered inside the rock.

“"They’re almost like miners … digging for water,” says David Kisailus, a chemical and environmental engineer at the University of California, Irvine, and one of the study’s authors. “They can actually search out and find the water and extract the water from these rocks.'”

Comment: An amazing group with very inventive ways of living. An enormous article filled with amazing descriptions of very strange bugs.