Theoretical origin of life; early anoxic bacteria (Introduction)

by David Turell , Friday, August 07, 2020, 20:53 (1569 days ago) @ David Turell

Had a metabolism without oxygen:

"In the first billion years, there was no oxygen on Earth. Life developed in an anoxic environment. Early bacteria probably obtained their energy by breaking down various substances by means of fermentation. However, there also seems to have been a kind of "oxygen-free respiration." This was suggested by studies on primordial microbes that are still found in anoxic habitats today.

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"...we at some point took a heat-loving bacterium, Thermotoga maritima, which grows at temperatures between 60 and 90°C," explains Dragan Trifunovic, who will shortly complete his doctorate. "Thermotoga also contains Rnf genes, and we hoped that the Rnf enzyme in this bacterium would be a bit more stable. Over the years, we then managed to develop a method for isolating the entire Rnf enzyme from the membrane of these bacteria."

"As the researchers report in their current paper, the enzyme complex functions a bit like a pumped-storage power plant that pumps water into a lake higher up and produces electricity via a turbine from the water flowing back down again.

"Only in the bacterial cell the Rnf enzyme (biochemical name = ferredoxin:NAD-oxidoreductase) transports sodium ions out of the cell's interior via the cell membrane to the outside and in so doing produces an electric field. This electric field is used to drive a cellular "turbine" (ATP synthase): It allows the sodium ions to flow back along the electric field into the cell's interior and in so doing it obtains energy in the form of the cellular energy currency ATP.

"The biochemical proof and the bioenergetic characterization of this primordial Rnf enzyme explains how first forms of life produced the central energy currency ATP. The Rnf enzyme evidently functions so well that it is still contained in many bacteria and some archaea today, in some pathogenic bacteria as well where the role of the Rnf enzyme is still entirely unclear."

Comment: It is important to remember all enzymes aere giant protein molecules with specific areas which force reactions to happen by keeping reactive molecules together. They are so specific they have to be designed.