Originally Posted by eburacum45

If we ever get the chance to explore many extrasolar worlds, we might find a certain number of them support such primitive pre-cellular biologies. By examining any such discoveries we could estimate how persistent and robust such biologies are, and maybe draw some conclusions about the origin of life on Earth.

This might be the only way we can ever investigate the process of abiogenesis directly, as the process (whether it happened as described in the way described in this article or not) will probably not be detectable in the fossil record.

Originally Posted by DrWho

10. Once protocells could generate their own electrochemical gradient, they were no longer tied to the vents. Cells left the vents on two separate occasions, with one exodus giving rise to bacteria and the other to archaea.

Originally Posted by "DrWho"

10. Once protocells could generate their own electrochemical gradient, they were no longer tied to the vents. Cells left the vents on two separate occasions, with one exodus giving rise to bacteria and the other to archaea.

Originally Posted by m74z00219

I find this one the most intriguing.

Originally Posted by m74z00219

I find this one the most intriguing. It gives credence to the notion that there may very well be alien life that is based on DNA.

Originally Posted by eburacum45

I don't know how long such a situation could persist, however; living, evolving cells can adapt to a wide variety of environments, but cell-less life would be limited to one environment and would die out as soon as that environment dissapeared.

Originally Posted by eburacum45

I find it interesting, but rather controversial. There may have been two separate 'cellular exodus' events, or just one, which then split up into bacteria and archaea. I don't think there is enough evidence to say one way or another, and there may never be.

Originally Posted by Henna Oji-san

I haven't read the article again, but I thought the point was that some differences between bacteria and archaea suggested they didn't have a common ancestor. But could be explained if they emerged at different times (or locations). Hardly conclusive though, I agree.

Originally Posted by Henna Oji-san

I haven't read the article again, but I thought the point was that some differences between bacteria and archaea suggested they didn't have a common ancestor.

Originally Posted by DrWho

Some interesting info in a New Scientist article: Was our oldest ancestor a proton-powered rock?


10 easy steps to life evolving in alkaline hydrothermal vents:

1. Water percolated down into newly formed rock under the sea floor, where it reacted with minerals such as olivine, producing a warm alkaline fluid rich in hydrogen, sulphides and other chemicals - a process called serpentinisation.

This hot fluid welled up at alkaline hydrothermal vents like those at the Lost City, a vent system discovered near the Mid-Atlantic Ridge in 2000.

2. Unlike today's seas, the early ocean was acidic and rich in dissolved iron. When upwelling hydrothermal fluids reacted with this primordial seawater, they produced carbonate rocks riddled with tiny pores and a "foam" of iron-sulphur bubbles.

3. Inside the iron-sulphur bubbles, hydrogen reacted with carbon dioxide, forming simple organic molecules such as methane, formate and acetate. Some of these reactions were catalysed by the iron-sulphur minerals. Similar iron-sulphur catalysts are still found at the heart of many proteins today.

4. The electrochemical gradient between the alkaline vent fluid and the acidic seawater leads to the spontaneous formation of acetyl phosphate and pyrophospate, which act just like adenosine triphosphate or ATP, the chemical that powers living cells.

These molecules drove the formation of amino acids – the building blocks of proteins – and nucleotides, the building blocks for RNA and DNA.

5. Thermal currents and diffusion within the vent pores concentrated larger molecules like nucleotides, driving the formation of RNA and DNA – and providing an ideal setting for their evolution into the world of DNA and proteins. Evolution got under way, with sets of molecules capable of producing more of themselves starting to dominate.

6. Fatty molecules coated the iron-sulphur froth and spontaneously formed cell-like bubbles. Some of these bubbles would have enclosed self-replicating sets of molecules – the first organic cells. The earliest protocells may have been elusive entities, though, often dissolving and reforming as they circulated within the vents.

7. The evolution of an enzyme called pyrophosphatase, which catalyses the production of pyrophosphate, allowed the protocells to extract more energy from the gradient between the alkaline vent fluid and the acidic ocean. This ancient enzyme is still found in many bacteria and archaea, the first two branches on the tree of life.

8. Some protocells started using ATP as well as acetyl phosphate and pyrophosphate. The production of ATP using energy from the electrochemical gradient is perfected with the evolution of the enzyme ATP synthase, found within all life today.

9. Protocells further from the main vent axis, where the natural electrochemical gradient is weaker, started to generate their own gradient by pumping protons across their membranes, using the energy released when carbon dioxide reacts with hydrogen.

This reaction yields only a small amount of energy, not enough to make ATP. By repeating the reaction and storing the energy in the form of an electrochemical gradient, however, protocells "saved up" enough energy for ATP production.

10. Once protocells could generate their own electrochemical gradient, they were no longer tied to the vents. Cells left the vents on two separate occasions, with one exodus giving rise to bacteria and the other to archaea.