The molecules that gave rise to life may have formed around seafloor vents like this one in the North Atlantic Ocean.
Credit: NOAA
SYDNEY: The first steps towards life may have been taken billions of years ago in the waters around seafloor vents, German researchers say.
Their study, published today in the U.S. journal Science, suggests that amino acids - the building blocks of all proteins - and other important organic molecules can form instantaneously under certain conditions with no ingredients other than seawater, volcanic gases, and metals which are present in the ocean floor.
Günter Wächtershäuser, and Claudia Huber of the Technical University of Munich in Germany have shown that, under the right conditions, metal atoms alone can catalyse the formation of amino acids, and even link them up in short strings called peptides - the first step toward creating proteins. Intriguingly, the results also suggest that once these peptides have been created, they actually bind to the metal atoms and increase their catalytic ability.
Most scientists think that the origin of life was a slow process of trial and error, taking place over millions of years. Eventually, complex molecules such as RNA (which help build DNA) and proteins were created that could replicate themselves. The team's findings suggest that the process may have been much quicker. "We [think] that life starts with an instantaneous chemical reaction that occurs when certain volcanic gases contact … metals such as nickel and iron," they said.
A class of proteins called enzymes act to speed up, or catalyse, most of the chemical reactions that occur in cells, including those that make amino acids and assemble them into enzymes. Without enzymes, the biochemical reactions that enable the cell to function would occur as much as a billion times slower.
One of the central paradoxes in the debate over the origin of life is how amino acids were originally created and assembled into enzymes when there were no enzymes around to catalyse the reaction. Many present-day enzymes are based around metal atoms, and the finding that metal atoms alone can create amino acids is a significant step forward in the debate over how life began.
The study tries to replicate the conditions present 4 billion years ago in the young oceans of Earth, when superheated volcanic gases rich in simple organic molecules like carbon monoxide and cyanide rose up through cracks in the seafloor. As the gases climbed through the rock, they mixed with seawater and encountered nickel and iron.
Other processes can create amino acids, said Wächtershäuser, but "this is important because it is a very selective process that generates 'alpha' amino acids." Alpha amino acids are the only ones that occur in life on Earth.
According to Wächtershäuser, now that he and Huber have demonstrated that it is possible to produce the building blocks of life instantaneously under volcanic conditions, they must demonstrate that these molecules can replicate themselves. "We have demonstrated production," said Wächtershäuser. "Now we must demonstrate reproduction."
