Small Volcanic Cracks May Have Been Ideal Environment for Ancient DNA
According to work done by researchers from the Ludwig Maximillian University of Munich, tiny pores in ancient Earth volcanic rocks may have created the perfect environment for replicating molecules and may have been responsible for driving genetic sequences to evolve longer and longer.
Genetic material in shorter fragments replicate faster than their longer counterparts. As such, the shorter fragments have a tendency to out-compete the longer ones, resulting in a trend that leads to information loss over time instead of longer strands developing. Dieter Braun and colleagues believe, however, that conditions favoring the opposite may have existed within tiny cracks inside hot volcanic rocks sitting on the sea bed millions of years ago.
Braun said that he and his colleagues thought that producing a thermal gradient in porous rock would be the simplest means of replicating a common setting in early Earth. They did not, however, expect that the setup would solve a lot of problems associated with life's origins.
For a study published in the journal Nature Chemistry, the researchers engineered an experiment designed to simulate conditions within rock pores. Glass capillary tubes were immersed in water flowing continuously. The water contained DNA fragments in different lengths. The capillary tubes were then heated on one side creating a temperature gradient.
Researchers found that some DNA fragments got trapped in one side of the tubes, accumulating to form a pocket full of DNA. Additionally, when polymerase enzymes, nucleotides and fluorescent-labeled primers into the system and left the setup running for a few hours, the DNA fragments replicated as they moved within the hot and cold areas inside the tubes.
Just a rock pore the size of a millimeter has the ability to accumulate molecules and keep them continuously replicating thanks to thermal cycling and the non-stop inflow of water. According to Braun, the process favors longer fragments of DNA or those strands made up of more than 75 nucleotide replicates. Shorter strands of DNA material were simply washed out of the tubes.
He also further explained that longer DNA strands were necessary for genetic information to evolve. In a way, the rock pores acted as miniature incubators, fostering the very building blocks of life.
Matthew Powner from University College London thinks the study's theory is convincing, adding more interesting things may be observed if the polynucleotide selection process was coupled with mutation and evolution. Powner was not involved with the study.
Aside from Braun, Simon Lanzmich, Lorenz Keil and Moritz Kreysing also contributed to the study.