Researchers have a new theory about the origins of life suggesting water-filled micropores in burning hot rocks could act as nurseries for the building blocks of living things.
The findings suggest temperature gradients in pore systems could give birth to cyclical replication and emergence of nucleic acids, reported Ludwig-Maximilians-Universität München.
In order for life to form simple biomolecules must be able to form more complex structures, but this process to occur there must be some means of accumulating the precursor molecules in highly concentrated form in solution. These solutions may have been available at low levels in the early oceans, but pore systems on the seafloor may be a more likely origin of Earth's life.
"The key requirement is that the heat source be localized on one side of the elongated pore, so that the water on that side is significantly warmer than that on the other," said Professor Dieter Braun.
Preformed biomolecules could have been washed into these pores and trapped by the temperature gradient. In this gradient charged molecules tend to move from warmer to cooler temperatures, allowing longer polymers to be secured. This is an important factor in the evolution of nucleic acids such as RNA and DNA. A team of researchers demonstrated this process in a laboratory setting.
"We used tiny glass capillary tubes to construct an analog of the natural pores found in rock, heated the pore from one side and allowed water containing dissolved fragments of linear DNA of varying lengths to percolate through it. Under such conditions, the long strands are indeed trapped within the pore," Braun said "Pores that were exposed to heat are frequently found in igneous rock formations, and they were certainly common in rocks of volcanic origin on the early Earth. So this scenario is quite realistic. And the temperature effect is enhanced by the presence of metal inclusions within the rock, which conduct heat at rates 100 times higher than water."
The researchers demonstrated nucleic acids can be retained in these pores and also have the ability to replicate. Once single strands are transported to the colder regions of the pore they encounter the chemical precursors from which each strand is built, and they act as "templates" for the polymerization of complementary strands. Once these strands replicate to a certain extent they are able to escape from the pore and colonize nearby pore systems.
"Life is fundamentally a thermodynamic non-equilibrium phenomenon. That is why the emergence of the first life-forms requires a local imbalance driven by an external energy source -- for example, by a temperature difference imposed from outside the system," Braun said. "That this can be achieved in such a simple and elegant way was surprising even to us. The success of the project is a tribute to the close cooperation between all members of the team."
The findings were published in a recent edition of the journal Nature Chemistry.
