UCSC's David Deamer performs an experiment on a volcanic pool.
On the ceiling of the Sistine Chapel, Michelangelo’s Creation of Adam depicts the origin of life as told by Christian theology. God’s hand reaches toward Adam’s, their fingers pointing outstretched. If UCSC biochemist David Deamer could paint himself into the fresco, his finger would point toward the slimy edge of an acidic, bubbling, volcanic pool.
“If I had to think of the origin of life,” says Deamer, “with apologies to Michelangelo, I think it would be right there.”
Deamer’s unique approach to studying how life began attracted the attention of scientists at NASA more than 30 years ago, and the space agency has funded much of his research since. His latest proposal earned a $60,000 prize from the Origin of Life Challenge, a competition sponsored by a retired entrepreneur.
This project may have revealed a new piece of the puzzle. Deamer and his colleagues at the NASA Ames Research Center in Mountain View found that when elements like carbon, nitrogen, oxygen and sulfur are released into space by dying stars, they react to form compounds like methanol, water and ammonia. When ultraviolet radiation and cosmic rays permeate those ingredients, they form even more complex structures—such as hydrocarbons, the constituent molecules of cell membranes.
Deamer thinks those interstellar molecules settled onto early Earth and gave rise to protocells, the first cells to exist. But it probably took some homegrown cooking to do that—and our young planet had plenty of volcanoes to stir the pot.
Alien Origins
The eastern edge of Russia’s remote Kamchatka Peninsula is peppered by 160 volcanoes, 29 of which are active (accounting for 10% of the world’s active volcanoes). In 2002 and 2004, Deamer and his team trekked to Kamchatka on expeditions funded by Nobel laureate Baruch Blumberg, then director of NASA’s astrobiology program. Deamer looked to one volcano in particular: Mount Mutnovsky. The mountain is a five-hour trip (via Russian troop carrier) outside of civilization. Atop its steep, snow-covered banks and amid piles of massive boulders lies a land he believes is nearly identical to our planet before life.
“When you go down the crater, this is what I think early Earth was like,” says Deamer. “Virtually sterile, nothing alive.”
The crater sits among a set of sloping hills. Bacteria and grasses grow on the lower hills, but the higher ones are devoid of life due to recent eruptions. Deamer once showed a picture of Mount Mutnovsky’s tortured landscape to a researcher with the Mars Curiosity program, who asked where on the Red Planet the picture was taken.
At the foot of Mutnovsky, large pipes jut out of the ground—built to harness energy, but abandoned long ago. Today, mineral crusts encapsulate the pipes, which perpetually spew steam into the air. When Deamer struck the crusty shell with a rock hammer, he exposed a thin, green layer sandwiched between white ice and gray calcium carbonate. It was cyanobacteria: ancient microorganisms that harness energy from photosynthesis.
Later in the weeklong expedition, he stood 2,000 feet above the mountain’s base. Peering from behind a black, rubber gas mask resting atop his gold-brimmed glasses, he collected samples by extending a long pole into steaming pits while fellow scientist Vladimir Kompanichenko steadied him. A towering glacier melted in the background, giving way to blooming white clouds around the 80-degree hot springs. The “soil” beneath his boots was pure sulfur.
Around him, noxious gases misted out of the ground: sandy patches mixed with rocky clay outcrops, filled with acidic, murky, softly bubbling soups. Lines along the brims of these pools showed where water levels rose and fell on regular cycles.
Life was increasingly sparse closer to the eruption zone, and pools next to the crater were completely sterile. But Deamer wasn’t searching for ancient protocells. Instead, he looked to Mutnovsky’s sterile pools to perform an informal science experiment.
What would happen, he thought, if asteroids or comets snatched up organic material from space about 4 billion years ago and delivered it into Earth’s volcanic pots? Alternatively, what would happen if a curious biochemist poured a lab-brewed milky-white soup of the same organic molecules into one of Kamchatka’s pools? The answer: something interesting.
When Deamer added his concoction, he saw one kind of molecule cluster at the pool’s edge. They were fatty acids: the hydrocarbon chains that link up to form cell membranes. Deamer had seen the same fatty acids 20 years earlier, when he discovered them inside a famous meteorite that fell onto Murchison, Australia.
Life’s Work
Deamer always had a thing for membranes. Early in his career, he studied their self-assembling properties at UC Davis. While other origin of life researchers looked to more famous molecules, Deamer thought membranes played a lead role in life’s genesis. That hunch brought him to Kamchatka—and led to his new take on primordial soup in his lab at UC Santa Cruz.
Deamer is, by all accounts, a seasoned professional scientist. But he sometimes follows an unconventional path. Chris McKay, a NASA Ames scientist and fellow origin of life researcher, explains that Deamer “takes an ‘out in the real world’ approach.
“That’s useful,” says McKay, “because nature can create conditions that are unexpected, and not programmed into laboratory simulations.”
Deamer’s soup-simulator on campus looks more like outdated stereo equipment than a place for life to begin. Inside an acrylic box sits a slowly spinning aluminum wheel. The wheel houses several small wells, in which Deamer and his students place some of the ingredients of life: fatty acids and the compounds that make up RNA (adenine, guanine, uracil and cytosine). The solution is warm and acidic. But Deamer claims the machine’s most important property is the wet-to-dry cycling that cause the soup’s water levels to fluctuate, just like in the odorous pools at Mutnovsky.
When the machine’s wells dry, fatty acids amass into membrane vesicles (cellular compartments). When they get wet again, the vesicles swallow the soup’s contents. Molecules that were once floating freely are now trapped inside. Chemicals must nestle close together for chemical reactions to occur within cells. Deamer’s vesicles, now protocells, provide the perfect place for that to happen.
If indeed fatty acids were the key to protocells, meteorites would have been their delivery system. The Murchison impact showed scientists that some meteorites are cosmic cornucopias, carrying thousands of carbon-containing molecules, including the building blocks of cells: fatty acids, amino acids and more.
In our own cells, highly specific molecular machinery assembles those pieces. But such complex machinery couldn’t have arisen first on the early Earth. There must have been a simpler assembly process, driven by environmental conditions and guided by something extra. Fatty acids may have been that something.
Within Deamer’s soup, the makeshift membranes assembled more than just themselves. They also started creating chains of nucleotides, the constituent molecules of RNA and DNA.
Nuclear Soup
RNA and DNA are nucleic acids. DNA stores our genetic information while RNA transcribes it, among other tasks. But many researchers believe RNA, which consists of a single strand, predated its double-stranded sister molecule in early life. Deamer’s research supports that hypothesis.
For nucleotides to link up and form a chain of RNA, they need two things: to be in an acidic environment, and to lose water molecules in a dehydration reaction. It also helps if the nucleotides line up correctly.
Deamer’s soup did all three.
As the reaction ran through many wet-dry cycles, it linked nucleotides together and the chain grew longer. The membrane vesicles formed an organizing matrix, much like a knitter’s loom, which assembled nucleotides into nucleic acids. But the researchers were unsure if it was truly RNA, so Deamer checked with a revolutionary tool of biotechnology: nanopore analysis.
Nanopores are the magic behind the MinIon: a new, $900 USB-driven gene sequencer. The pores are riddled across a membrane template. When a piece of DNA or RNA comes across the pore, it gets sucked in and is, as Deamer says, “pulled through like a piece of spaghetti.”
Every nucleotide has a signature electrical pulse that lights up a tiny sensor attached to the pore. By reading the pulses, Deamer confirmed that his primordial polymer did indeed look like RNA. The product could be different from the RNA we know today, perhaps an earlier version. But before he dubs it so, the product needs to run a full gamut of tests. He should know exactly what he’s created this summer.
It’s Alive?
If it is RNA, will Deamer’s protocells be alive? Not exactly. But it’s a step in the right direction.
He may be able to show how gene-coding and expressing molecules could have spontaneously come into existence, completely from scratch. His simulations can explain the transitional steps from stardust to bubbling brew to cell parts to RNA-carrying protocells.
But those few steps have big implications. McKay, who recently delivered a lecture about life on other planets at the Rio Theater, explains the weight of Deamer’s discovery. “If David can demonstrate the formation of a cellular system in these experiments,” says McKay, “it would have profound implications for the study of the origin of life.”
Future researchers will need to demonstrate how protocells could evolve into fully functional cells, capable of crafting their own parts and reproducing.
But before Dr. Frankenstein’s famous words can be uttered, much work remains. Even the most advanced protocells must satisfy strict criteria before they can join the living.
Until then, Deamer wants to bring his recipe to another volcanic pool and brew RNA in the wild.
“I’m going to take my little stuff,” says Deamer, “find a rock, pour some on, come back the next day and see whether we haven’t made some RNA. That’d be the final nail in the coffin.”
