Theoretical origin of life; subterranean extremophiles (Introduction)

by David Turell , Tuesday, October 02, 2018, 01:03 (2244 days ago) @ Balance_Maintained

David: A review article about how varied they are, and the strange types of energy they use:

https://www.the-scientist.com/features/life-thrives-within-the-earths-crust-64805?utm_c...

"These expeditions are just one part of a rapidly expanding field of research focused on documenting microbial and even eukaryotic life dwelling hundreds of meters deep in the Earth’s crust—the vast sheath of rock encasing the planet’s mantle. Researchers are now exploring this living underworld, or deep biosphere, not only in the ancient, slow-changing continental crust beneath our feet, but in the thinner, more dynamic oceanic crust under the seafloor.

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"To date, studies of crustal sites all over the world—both oceanic and continental—have documented all sorts of organisms getting by in environments that, until recently, were deemed inhospitable, with some theoretical estimates now suggesting life might survive at least 10 kilometers into the crust. And the deep biosphere doesn’t just comprise bacteria and archaea, as once thought; researchers now know that the subsurface contains various fungal species, and even the occasional animal. Following the 2011 discovery of nematode worms in a South African gold mine, an intensive two-year survey turned up members of four invertebrate phyla—flatworms, rotifers, segmented worms, and arthropods—living 1.4 kilometers below the Earth’s surface.

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"A key area of research now is understanding how such life survives. Devoid of sunlight, “these systems are typically energy-poor,” says Sherwood Lollar. Compared to surface communities, microbes in the deep biosphere are thought to be relatively slow-growing and sparsely distributed, she adds. While surface soil may contain in excess of 10 billion microbes per gram, oceanic crust usually contains around 10,000 cells per gram, and continental crust—where water is unsurprisingly in shorter supply—holds fewer than 1,000 cells per gram.

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"When geomicrobiologist Lotta Purkamo of the University of St Andrews and her colleagues characterized the ecosystem of a 600-meter-deep borehole in northern Finland, for example, they found evidence of metabolic pathways based on reducing or oxidizing sulfate, nitrate, methane, ammonia, and iron, as well as fixation reactions involving carbon.(Bold Mine)

Additionally, thanks to metatranscriptomic analyses, “we’re learning that these organisms have a lot of potential metabolisms that they could be expressing,” says Huber, who recently carried out this sort of assay on the Axial Seamount community.12 “But depending on the conditions and the geological setting, just a small subset of those genes are being used.” Such results hint at flexible and opportunistic lifestyles, she adds, where microbes make use of whatever they can, whenever they can.

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"Researchers are far from agreeing on the extent of this underworld—one 1990s paper controversially suggested that deep life constituted 50 percent of the Earth’s current biomass, though most estimates are now below 15 percent. Before the rise of land plants around 400 million years ago, though, deep biomass could have outweighed life on the surface by an order of magnitude, according to calculations published this summer by McMahon and the University of Aberdeen’s John Parnell.

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“'When we think about how life on Earth has changed over time, and how it’s interacted with the chemistry of rocks, sediments, groundwater, oceans, atmosphere, we shouldn’t be thinking just about charismatic animals and plants,” says McMahon. “We should be thinking about this huge quantity of microorganisms, most of which are living on the surfaces of mineral grains and interacting with them.'”

Comment: This type of research makes it seem that given the right planet, life is easy to begin in many different ways on many different substrates.

Tony: Terraforming bacteria. Unsurprising as it fits with my speculation that early microbes were designed to terraform the planet.

It certainly does, as it seems life can handle any conditions