Extreme extremophiles: from ocean cores (Introduction)

by David Turell , Thursday, October 29, 2020, 14:28 (1274 days ago) @ David Turell

Very difficult to revive:

http://nautil.us/issue/92/frontiers/preserving-a-sense-of-wonder-in-dna?mc_cid=68eb156a...

"When we go beyond the top 10 centimeters where animals tend to be burrowing, there’s very little mixing and reworking of the marine sediments, he said. There are marine locations which have not had significant perturbations for millions of years.

"These habitats are hard to mimic in the laboratory given their extreme energy limitations. Among the habitats that Bradley studies is the South Pacific Gyre. The crew of the ship JOIDES Resolution drilled a long vertical core from the gyre, wearing masks to protect themselves from the hydrogen sulphide gas the core emits. Such cores can be hundreds of meters long, taken up in sections.

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“'From analyzing what is contained in this core, from the top of it to the bottom of it, you’re going from a modern environment, all the way to an ancient environment,” said Bradley. From the South Pacific gyre, the cores can date upward of 95 million years old.4 The hydrogen sulphide is a byproduct of metabolism. That this is measured is a “good indication we have living and breathing organisms that are surviving in this habitat,” he said. In a 2018 paper, writing about the Deep Biosphere, Bradley noted, “the fitness of a microorganism may not be determined by its growth, but rather its ability simply to stay alive.”

"He is particularly interested in understanding what the energy limits may be for such organisms. “That is a tough line to draw,” he said, “because the amount of energy that these organisms are processing is so close to zero.” There is an energetic shift from when organisms are in growth mode and move to maintenance mode, and then to what Bradley calls a “deeper state of dormancy.” He said, “It’s reduced its basal maintenance energy requirement to even lower than it was previously, where it was not growing.”

"A human typically runs on 100 watts of power while an organism from the deep subsurface theoretically may run at about 10 to the power of -21 watts. “So that’s more than a hundred billion-billion, I’m not sure how many billions…” times lower than the power that a human runs on, he said. The -21 is a theoretical limit though, and Bradley estimates that organisms would be subsisting at a higher power threshold.

"Bradley points to a surreal aspect. Experimentalists struggle to grow and culture these ancient organisms. To his knowledge, the time taken for them to revive has taken up to 1,000 days. For organisms that did not revive, it is possible that the variable that’s missing is not nutrients but time for the super-slow organisms to grow. “We might be testing conditions in the lab over too small a time scale,” he said."

Comment: Apparently, as described before living organisms can be exceedingly tough and survive in very severe conditions. Adaptability in the extreme is built into life.