Theoretical origin of life; early anoxic bacteria (Introduction)

by David Turell , Wednesday, September 23, 2020, 01:23 (1526 days ago) @ David Turell

Perhaps using arsenic:

https://www.sciencedaily.com/releases/2020/09/200922112236.htm

"Much of life on planet Earth today relies on oxygen to exist, but before oxygen was present on our blue planet, lifeforms likely used arsenic instead.

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"Theories as to how life's processes functioned in the absence of oxygen have mostly relied on hydrogen, sulfur, or iron as the elements that ferried electrons around to fulfill the metabolic needs of organisms.

"Visscher explains these theories are contested, for example photosynthesis is possible with iron but researchers do not find evidence of that in the fossil record before oxygen appeared some 2.4 billion years ago. Hydrogen is mentioned yet the energetics and competition for hydrogen between different microbes shows it is highly unfeasible.

"Arsenic is another theoretical possibility, and evidence for that was found in 2008. Visscher says the link with arsenic was strengthened in 2014 when he and colleagues found evidence of arsenic-based photosynthesis in deep time. To further support their theory, the researchers needed to find a modern analog to study the biogeochemistry and element cycling.

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"However, a breakthrough happened when the team discovered an active microbial mat, currently existing in the harsh conditions in Laguna La Brava in the Atacama Desert in Chile.

"The mats have not been studied previously but present an otherworldly set of conditions, like those of early Earth. The mats are in a unique environment which leaves them in a permanent oxygen-free state at high altitude where they are exposed to wild, daily temperature swings, and high UV conditions. The mats serve as powerful and informative tools for truly understanding life in the conditions of early Earth.

"Visscher explains, "We started working in Chile, where I found a blood red river. The red sediments are made up by anoxogenic photosynthetic bacteria. The water is very high in arsenic as well. The water that flows over the mats contains hydrogen sulfide that is volcanic in origin and it flows very rapidly over these mats. There is absolutely no oxygen."

"The team also showed that the mats were making carbonate deposits and creating a new generation of stromatolites. The carbonate materials also showed evidence for arsenic cycling -- that arsenic is serving as a vehicle for electrons -- proving that the microbes are actively metabolizing arsenic much like oxygen in modern systems. Visscher says that these findings, along with the fossil evidence gives a strong indication of what was seen on early earth.

"'Arsenic-based life has been a question in terms of does it have biological role or is it just a toxic compound?" says Visscher. That question appears to be answered, "I have been working with microbial mats for about 35 years or so. This is the only system on Earth where I could find a microbial mat that worked absolutely in the absence of oxygen.'"

Since life dates back to 3.8 bya, it had to exist somehow. This appears to be the how. What is of great interest is that life depends on arsenic, a poison, or oxygen, a dangerous element because it causes unwanted oxidation so easily, i.e., forest fires. So we have to ask, why God would choose this approach? Answer, it must be the best one.