L1 Did black volcanic rock help early life 753w 5m

Volcanic glass, like that found near Iceland’s Blue Lagoon, can help knit RNA letters into long strands.
Did black volcanic rock help spark early life?
Quenched lava may have helped form long RNA strands vital to primordial organisms
By Robert F. Service
W
hen life emerged, it did so quickly.
Fossils suggest microbes were
present 3.7 billion years ago, just
a few hundred million years after
the 4.5-billion-year-old planet had
cooled enough to support biochemistry. Many researchers think the hereditary material for these first organisms
was RNA. Although not as complex as DNA,
RNA would still be difficult to forge into the
long strands needed to convey genetic information, raising the question of how it could
have spontaneously formed.
Now, researchers may have an answer.
In lab experiments, they show how rocks
called basaltic glasses help individual RNA
letters, known as nucleoside triphosphates,
link into strands up to 200 letters long. The
glasses would have been abundant in the fire
and brimstone of early Earth; they are created when lava is quenched in air or water
or when the melted rock created in asteroid
strikes cools off rapidly.
The result has divided top origin-of-life
researchers. “This seems to be a wonderful
story that finally explains how the nucleoside
triphosphates react with each other to give
RNA strands,” says Thomas Carell, a chemist at the Ludwig Maximilian University of
Munich. But Jack Szostak, an RNA expert at
Harvard University, says he won’t believe the
result until the research team better characterizes the RNA strands.
Origin-of-life researchers are fond of a primordial “RNA world” because the molecule
can carry out two distinct processes vital for
life. Like DNA, it’s made up of four chemical
letters that can carry genetic information.
And like proteins, RNA can catalyze chemical
reactions needed for life.
But RNA also brings headaches. No one has
found a set of plausible prebiotic conditions
that would cause hundreds of RNA letters—
each of them complex molecules—to link into
strands long enough to support the complex
chemistry needed to ignite evolution.
Stephen Mojzsis, a geologist now at the Research Centre for Astronomy and Earth Sciences of the Hungarian Academy of Sciences,
wondered whether basaltic glasses played a
role. They are rich in metals such as magnesium and iron that promote many chemical
reactions. And, he says, “Basaltic glass was
everywhere on Earth at the time.”
He sent samples of five different basaltic
glasses to the Foundation for Applied Molecular Evolution. There, Elisa Biondi, a molecular biologist, and her colleagues ground
each sample into a fine powder, sterilized
it, and mixed it with a solution of nucleoside triphosphates. Without a glass powder
present, the RNA letters failed to link up.
But when mixed with the glass powders,
the molecules joined into long strands,
some hundreds of letters long, the researchers report last week in Astrobiology. No
heat or light was needed. “All we had to do
was wait,” Biondi says. Small RNA strands
formed after just a day, but strands kept
growing for months. “The beauty of this
model is its simplicity,” says Jan Špaček, a
molecular biologist at Firebird Biomolecular Sciences. “Mix the ingredients, wait for a
few days, and detect the RNA.”
Still, the results leave questions unanswered. One is how the nucleoside triphosphates could have arisen in the first place.
Biondi’s colleague Steven Benner says recent
research shows how the same basaltic glasses
could have promoted the formation and stabilization of the individual RNA letters.
A bigger issue, Szostak says, is the shape of
the RNA strands. In modern cells, enzymes
ensure most RNAs grow into linear chains.
But RNA can also bind in complex branching patterns. Szostak wants the researchers
to report which type of RNA the basaltic
glasses created. “I find it very frustrating that
the authors have made an interesting initial
finding but then decided to go with the hype
rather than the science,” he says.
Biondi admits her team’s experiment almost certainly produces a small amount of
RNA branching. However, she notes that
some branched RNAs exist in organisms today, and related structures may have been
present at life’s dawn. She also says other
tests the group performed confirm the presence of long strands with connections that
most likely mean they are linear. “It’s a
healthy debate,” says Dieter Braun, an originof-life chemist at Ludwig Maximilian. “It will
trigger the next round of experiments.” j