Nearly 4 billion years after life first arose on Earth, researchers have been trying to recreate the first steps towards life in steamy, bubbling pools in New Zealand.
One of the big questions in understanding the origins of life is how smaller molecules like nucleotides, fatty acids, or amino acids first formed long, polymer chains like RNA, lipids, and proteins. Life as we know it uses RNA and DNA as its genetic material, while proteins look after and catalyse these and other processes, all encapsulated within the lipid membranes that surround each living cell.
Previous lab experiments by David Deamer of the University of California, Santa Cruz, and his colleagues have demonstrated that basic, cell-like structures 鈥� called protocells 鈥� can form in hot-spring like conditions, with temperatures of 80 to 90 centigrade聽and repeated cycles of drying and rehydration. These conditions can bring simple molecules together and encourage them to form the long polymer chains essential for life. If lipid molecules are present too, this simulated environment can cause these polymers to become encapsulated inside fatty membranes that are similar to those seen on the outside of all cells today.
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But it wasn鈥檛 known if these laboratory findings could really happen in real-world conditions. To find out, Deamer鈥檚 colleague Bruce Damer travelled to Hell鈥檚 Gate near the town of Rotorua in New Zealand. This active geothermal area with acidic hot springs is 鈥渓ike a chemistry experiment that nature is carrying out,鈥� says Damer.
He placed glass vials containing a 鈥減rebiotic soup鈥� into a near-boiling pool. This soup contained fatty acids and glyceride, another component of lipids. The mix also included two components of the building blocks of RNA, which is widely believed to have been life鈥檚 original genetic material, before DNA was adopted.
The hot spring water heated the soup to around 90 centigrade, and when it dried out, Damer repeatedly wetted it with water from a nearby acidic pool, with a pH of around 1.5, that had been filtered to remove any microorganisms. The idea was to mimic water splashing from geyser eruptions, but on a faster timescale and without contamination from existing lifeforms.
Dried films became visible on the glass of the vial, and subsequent tests revealed that long RNA-like molecules had formed within these fatty layers. Deamer says he believes this is the first time anyone has tested laboratory results out in a real environment similar to the kinds of places that would have existed when life began. The results are due to be published in Astrobiology soon.
In further lab-based experiments, Deamer鈥檚 team have also found than the presence of nucleic acids appears to help fatty acid molecules to form relatively large, fluid-containing sacs. This suggests the genetic polymers needed for life may also help stabilise the rudimentary cells containing them.
But John Sutherland, of the MRC Laboratory of Molecular Biology in Cambridge, UK, warns that the experiment did not make RNA itself, and says he doesn鈥檛 think that the 鈥淩NA-like鈥� polymers that formed are relevant to origins-of-life chemistry.
鈥淚t鈥檚 quite neat work, but needs replicating,鈥� says Nick Lane of University College London. The problem is that there is no obvious path from these results to cells that have a metabolism and can reproduce themselves, he says.
