Scientists Warn of an ‘Unprecedented Risk’ From Synthetic ‘Mirror Life,’ Built With a Reverse Version of Natural Proteins and Sugars

On Thursday, a group of notable scientists, including Nobel Prize winners and global health experts, issued a warning against researchers synthesizing a type of artificial cell that could rampage through life on Earth with practically no barriers to stop it.

“Mirror cells,” as they are known, could one day compose “mirror life,” a type of synthetic organism that, on the molecular level, is the complete reverse of the life forms we know. But the 38 co-authors of the warning article published in the journal Science recommend that research into mirror life be blocked immediately, before it spirals out of control.

To understand mirror life, consider good old-fashioned life. The building blocks of life, like DNA and proteins, all have a property called chirality. Derived from the Greek word for “handedness,” chirality means that these fundamental biomolecules come in two varieties: with either a right-handed or left-handed orientation. DNA, for instance, is made up of a right-handed double helix of sugars, like a ladder twisted only in a certain direction. Proteins, by contrast, are made up of left-handed amino acids.

“The opposite hands for both amino acids and sugars exist in the universe, but they just aren’t utilized by any known biological life form,” Danielle Sedbrook wrote for Smithsonian magazine in 2016. That selection is “one of the strangest aspects of life on Earth.”

Right- and left-handed molecules are not interchangeable, just like how your left hand won’t neatly fit into your right-handed glove. However, when you hold your left hand up to a mirror, it appears as if it were the same orientation as your right.

In recent years, scientists have begun to synthetically create these “mirror” versions of real-life molecules—right-handed proteins and left-handed sugars—in the lab.

Should this research continue into building mirror cells, “the consequences could be globally disastrous,” Jack Szostak, a Nobel Prize-winning chemist at the University of Chicago and co-author of the new article, tells Carl Zimmer of the New York Times. 

The profound consequences start at a molecular level. Right-handed amino acids seem quite similar to their left-handed counterparts. But in fact, they’re significantly harder to break down, because the enzymes in Earth’s life are built to degrade proteins with left-handed chirality. To use an analogy from the New York Times, you can’t twist open a lid counterclockwise when the threads run the opposite direction.

To optimists, this property of mirror molecules could prove useful in the fight against chronic disease.

“If you give therapeutics to a person, especially protein or nucleic acid therapeutics, digestive enzymes in the body break them down rapidly, sometimes within minutes,” Michael Kay, a biochemist at the University of Utah and a co-author of the warning in Science, says in a statement. “This can make it very challenging to treat chronic illnesses in a way that’s cost-effective and convenient.”

Mirror molecules, on the other hand, “are not recognized by those digestive enzymes,” Kay adds, opening up the possibility that they could remain effective as therapeutics for “a much longer period of time.”

Kay Lab D-Peptide Discovery

Watch on

But this same property could also make the cells dangerous. In a 299-page technical report that accompanied the article in Science, the team highlighted how “sufficiently robust mirror bacteria could spread through the environment unchecked by natural biological controls.”

The effects of these potentially “dangerous opportunistic pathogens,” the authors write, would extend to “an unprecedentedly wide range of other multicellular organisms, including humans.”

Mirror cells constructed in a lab could infect workers “without triggering any resistance from their immune systems,” according to the New York Times. From there, the cells could spread with similar stealth until a “mirror pandemic” gets out of control.

These synthetic life forms would threaten more than just humans. Other animals and plants would put up similarly weak defenses. Entire ecosystems could be at risk. “The impact on the food chain would be devastating,” Deepa Agashe, a biologist at the National Center for Biological Sciences in India, tells the Times.

This doomsday scenario sounds like science fiction. But the authors of the warning, many of them synthetic biologists, are acutely aware of the dangers that their research, if unchecked, could pose to the world.

“We think there’s an opportunity, before anyone’s livelihood depends on this, to define responsible lines of research, lines that should be carefully evaluated by regulatory authorities, and the lines we shouldn’t cross,” Kay says in the statement.

In a separate article published in the Scientist, John Glass and Kate Adamala, both synthetic biologists who also signed onto the article in Science, argue that the risks of this work far outweigh the benefits.

“Curiosity is not a good enough reason to create something that could be so dangerous,” they write. “For the good of mankind—and science itself—we must avoid the creation of mirror life.”

Eli Wizevich | | READ MORE

Eli Wizevich is a history correspondent for Smithsonian. He studied history at the University of Chicago and previously wrote for the El Paso Times.