Part animal, part vegetable, part microbe, an entirely new assemblage of cellular machinery makes useful chemical building blocks out of planet-warming carbon dioxide, and does it more efficiently than plants do.
Researchers from one of the Max Planck Institutes in Germany have combined enzymes from nine different species to create a novel new way to "fix" CO2, turning it from a gas into an organic compound that can be used to make fuels, plastics, drugs and more.
The experimental system, described in the journal Science, is a long way from practical application. But it shows that enzymes from all walks of life can work together to create a system that outperforms photosynthesis, one of the most important and widespread chemical processes on Earth.
And if it can be scaled up, this chimera could help fight climate change.
Balky engine
Plants build their leaves, roots and branches out of carbon dioxide they remove from the atmosphere through photosynthesis. But humans are dumping more CO2 into the atmosphere than plants can remove.
The engine that runs photosynthesis, an enzyme known as RuBisCO, is notoriously slow and prone to backfiring. Scientists have tried to rev it up, but their modifications have been only moderately successful.
Tobias Erb and his colleagues at the Max Planck Institute previously found an enzyme in a strain of purple bacteria that's 20 times faster than RuBisCO.
"Our idea was, now, take this enzyme and reinvent CO2 fixation on the basis of this new enzyme we have discovered," he said.
Beautiful 'monster'
Their redesigned system includes one enzyme from a plant, one from humans and 15 others from seven different species of microorganism. Three enzymes got an additional bit of molecular tweaking to make them run better.
In a test tube, the reaction is about twice as fast and 20 percent more efficient than the one produced by plants, using the same amount of light.
"It's a beautiful version of a Frankenstein's monster," said Amanda Smeigh at the Solar Fuels Institute, who was not involved with the research.
"[It's] thrilling that they were able to bring so many species together and have it work." But it's a bit disturbing at the same time, she added. "If you're a sci-fi fan, that gets to the terrifying [question], 'What's going to come next?' "
"This one, I firmly believe will better society," she said. It shows it's possible to re-engineer natural systems to produce new fuels, drugs, materials or other products.
There are some downsides, according to a commentary accompanying the study. The system produces a molecular building block that's a bit harder to work with than what photosynthesis produces. And it will be too expensive and impractical to scale up in its current state.
Erb said the next step is to try to design artificial leaves or customized algae that run on their synthetic version of photosynthesis.
