Theoretical origin of life: very early chemical use (Introduction)

by David Turell , Sunday, May 18, 2025, 17:31 (2 days ago) @ David Turell

Another view of the study:

https://www.sciencealert.com/scientists-recreated-the-ancient-chemical-reactions-that-m...

"Life on Earth probably began in warm, underwater 'chemical gardens', rich in hydrogen and iron. Researchers from Germany have now simulated this environment in a vial, and found that archaic life forms that live in the deep sea today can thrive under these primordial conditions.

"It's difficult to imagine how life kicked off on our planet. In ecosystems today, life is so deeply entwined with itself that very few creatures live directly off Earth's raw materials. That has been the case for a very, very long time. (my bold)

"But the first organisms on an otherwise lifeless planet would have had to make do with what the mineral environment had to offer. There was little to no oxygen, and no photosynthesis.

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"Borrowing electrons from hydrogen as it spews from the Earth's core, the deep-sea microbes follow a recipe more ancient than the genes they use to conduct it, called the acetyl CoA pathway. It is the only method for carbon fixation – processing inorganic carbon into organic compounds – that can be re-created without enzymes.(my bold)

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"'The ancient occurrence of hydrothermal iron-sulfide rich deposits in the geological record extend into the early Archaean eon (4 to 3.6 billion years ago) and exhibit fossil features interpreted as some of the oldest signatures for life on Earth," the team writes in their paper describing the experiment.

"'However, links between abiotic H2 [dihydrogen] production in iron-sulfide chemical gardens simulating [primordial] hydrothermal systems and early life are scarce."

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"'Abiotic H2 was a potentially important electron donor and CO2 served as a key electron acceptor for the first cells," the team explains. "Anaerobic organisms that use the H2-dependent reductive acetyl CoA pathway for CO2 fixation are modern representatives that have preserved vestiges of the first metabolisms."

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"This is evidence that the recipe for acetyl CoA metabolism emerged from the extreme and energy-limited environments where Earth life may have struck its first sparks.

"'Our study points to mackinawite and greigite chemical gardens as potential hatcheries of life, primordial environments that could theoretically support a continuous evolution of the first metabolizing cells," the authors conclude.'

Comment: Amazing work to how early life invented mechanisms to live on very simple substrates. As an aside to dhw note: "In ecosystems today, life is so deeply entwined with itself that very few creatures live directly off Earth's raw materials. That has been the case for a very, very long time." When I have told you the ecosystems are exquisitely entwined this statement proves the point.