Extreme extremophiles: living in deep Earth mines: (Introduction)

by David Turell , Wednesday, December 13, 2023, 23:41 (136 days ago) @ David Turell

One in South Dakota:

https://www.scientificamerican.com/article/subterranean-microbial-dark-matter-reveals-a...

"Devoid of light and deprived of nutrients, the depths of Earth might seem too barren to bother scouring for signs of life. But subterranean microbial organisms actually make up an enormous part of our planet’s biosphere. They are second only to plants in terms of total estimated biomass.

"Now an abandoned gold mine in South Dakota is allowing the deepest look yet into this secret world of buried biodiversity. In new research published in the journal Environmental Microbiology, a genetic analysis of the mine’s microbes from as deep as 1.5 kilometers beneath the surface reveals a schism in survival strategies. Some microbes have big, bulky genomes that prep them to digest any nutrient that might come their way. Others are so genetically streamlined that they can’t even make some of life’s fundamental building blocks and instead rely on scavenging them or living symbiotically with other species.

“'It was just cool to find that total dichotomy in survival strategy,” says Lily Momper, a consultant at the environmental and engineering firm Exponent and the paper’s first author. Similar results have been seen at the few other deep microbe observation sites around the world, Momper says. “We think this is probably a strategy in the deep subsurface in general,” she adds.

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"The Deep Mine Microbial Observatory, a network of deep boreholes situated in what was once the Homestake gold mine in the Black Hills of South Dakota, is one of the few places on Earth where researchers can study these deep communities over long periods of time. “There are very few such deep boreholes,” Anantharaman says.

"The mine, which closed in 2002, penetrates 2,438 meters deep. Since 2007 it’s been a multidisciplinary science lab called the Sanford Underground Research Facility, and it is now used primarily by physicists who are studying neutrinos and searching for dark matter particles. But there is another type of “dark matter” down there, Osburn says: microbes that have never been cultured in a lab. They are only known from their genetic detritus, snippets and parcels of DNA that researchers can sequence en masse from filtered groundwater and painstakingly reconstruct. Retrieving these precious samples requires descending deep into the mine in a wood-and-metal elevator cage.

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"This method revealed genomes that were never seen before, indicating a plethora of new species hiding in the former gold mine’s depths. The researchers also found a large amount of diversity among the organisms. “The thing that popped out at us immediately is that they’re doing a lot,” Osburn says. “The metabolic capacity of these organisms is wide, so there’s huge potential for nitrogen and sulfur and metal cycling all over.”

"Some of the organisms were minimalists, with genes for only a few very specific metabolic processes. These weren’t surprising to see in a nutrient-poor place such as the subsurface, Anantharaman says, because there is a metabolic burden associated with maintaining a big, energy-hungry genome. More surprising, he says, was the discovery of a second class of maximalist organisms. These organisms had the ability to metabolize chemicals that were not found in their environment.

"This overpreparation is surprising because there is an energy cost to maintaining so many genes for so many metabolic abilities, Osburn says. But the “prepper” nature of these microbes may be an advantage in the subsurface. “Fractures open; fractures close; things mineralize,” she says. “Many of these organisms are just prepared for whatever energy source comes along.”

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"One common pattern, though, is that most sites host a wide range of life. Osburn and her team are now looking at sequencing not just DNA but RNA, the molecular go-between for genes and proteins. Studying microbial RNA can reveal not just what microbes can do, Osburn says, but what they are doing at a given moment. Another current project is analyzing subsurface biofilms—stable accumulations of microbes that are protected by slimy excretions, which we more typically encounter as scummy deposits in toilets and kitchen sinks. Biofilms are hard to study, Osburn says, but the researchers got lucky: They set up a long-term filtration system in a mine borehole in December 2019 and planned to collect it three to six months later. Instead COVID hit, and the filtration system sat for four years before the team could get back to check on it. Miraculously, it was intact."

Comment: all of these studies tell us the same thing: the form of life God created is tough enough to live anywhere on Earth. One wonders was first life this tough to start it all.