Old Extremophiles: using arsenic for energy (Introduction)

by David Turell , Friday, January 01, 2021, 15:31 (1422 days ago) @ David Turell

A new artic le about this research:

https://theconversation.com/ancient-microbial-life-used-arsenic-to-thrive-in-a-world-wi...

"Our team of geologists, physicists and biologists had found hints in fossilized stromatolites that arsenic was the chemical of choice for ancient photosynthesis and respiration. But modern-day versions of these microbial communities still live on Earth today. Perhaps one of these used arsenic and could offer proof for our theory?

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"In 2014, our team found the first clue that stromatolites were produced by arsenic-assisted photosynthesis and respiration. We collected pieces of 2.72-billion-year-old stromatolites from the pre-oxygen world by drilling into an ancient reefs in the Outback of Australia.

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"Our destination was Laguna La Brava, a very salty shallow lake deep into the harsh desert. A shallow stream, fed by a volcanic groundwater spring, led into the lake. The streambed was a unique, deep purple color. The color came from a microbial mat, thriving quite happily in waters that contained unusually high amounts of arsenic, sulfur and lithium, but missing one important element – oxygen.

"We cut a piece of the mat and looked for evidence of minerals. A drop of acid made the minerals fizz – carbonates! – this microbe community was forming stromatolites. So our team went to work, camping out at the site for days at a time.

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"All that was left was to show that the two types of arsenic could be detected in the modern stromatolites. We went back to France, and using an X-ray emission technique made chemical maps from the Chilean samples. Every experiment we performed supported the presence of a vigorous arsenic cycle in the absence of oxygen in this unique modern stromatolite. This validates, beyond doubt, the idea that the fossil Australian samples that we studied in 2014 held evidence of an active arsenic cycle in deep time on our young planet."

Comment: Before oxygen and photo synthesis there had to be another method to be designed.