The Wild Type is a weekly look at the most interesting thing happening in biotech, written for the curious rather than the credentialed. I am Riya, a biology student, and each issue is one idea, explained properly, in about five minutes. No background required.
This week: everything alive is built the same way round, and what it would take to build something that is not.
The Lead
In 1981 someone patented a sugar with no calories.
It is not an artificial sweetener. It is glucose, the same atoms in the same order as the sugar in your kitchen, and when it was put in front of a taste panel nobody could tell the two apart. It dissolves like sugar and browns like sugar. It simply passes straight through you without being absorbed, because your body has no way of taking hold of it.
The only difference is that it has been built the other way round.
Molecules can come in two versions that are mirror images of one another, the way your left and right hands are the same hand reflected. Chemists call this chirality, from the Greek word for hand. Left-handed scissors exist for this reason: in the wrong hand the blades push apart instead of together and the paper folds rather than cuts. A molecule has no equivalent of struggling through. It either fits the machinery that handles it or nothing happens at all.
Your digestive enzymes are shaped to grip ordinary sugar. Hand them the mirrored version and they slide off, so the sugar arrives, tastes sweet, and leaves again untouched.
Every living thing on Earth is built to the same orientation. Every protein in every organism, in you and in mushrooms and in whales and in the bacteria a mile under Antarctic ice, is made from left-handed amino acids. Every strand of DNA runs on right-handed sugars. Chemistry has no preference either way; make amino acids from scratch in a laboratory and you get a fifty-fifty mixture. Life picked a side near the beginning and has never once switched.
Which means the mirrored version of biology is not a place where anything has gone extinct. Nothing has ever lived there at all.
The Big Picture
That sugar has never reached a shop, because making it costs somewhere between a hundred and a thousand times more than making the ordinary kind. The chemistry works and the taste works. The price does not.
The same trick is worth far more in medicine than in food. Your body is efficient at destroying drugs, which is why a dose wears off and you have to take another one: enzymes find the molecule, grip it, and take it apart. Build that molecule mirrored and there is nothing for them to grip, so something that would have survived minutes can survive days instead.
A Berlin company called TME Pharma, founded in 1997, has spent nearly thirty years building mirror-image RNA, which it calls Spiegelmers after the German word for mirror. Ordinary RNA is a promising drug and a hopeless one at the same time: you can fold it into a shape that latches onto a single target in the body, and blood is full of enzymes that shred it within minutes of arrival. Built backwards, it slips past them. The company's lead candidate strips away a signal that brain tumours use to shield themselves, and it is in trials in patients whose cancer does not respond to standard chemotherapy.
Every one of those molecules is assembled by chemists, link by link, at chemist prices. Thirty years in, the science is not the thing holding this back. Manufacturing is.
The Gap
There has always been a cheaper way to make a complicated molecule, which is to grow it instead of building it. Beer, penicillin, insulin, most of what sits in your medicine cabinet: nobody assembles those by hand. You feed raw material to living cells in a tank and they do the work for nothing.
That option is closed here. Every organism on Earth is built the normal way round, so everything it makes comes out the normal way round too. There is no bacterium anywhere that will brew you mirror sugar, because there is no mirrored life to ask.
So in 2019 a group of biologists took about four million dollars to go and make some.
The proposal was serious for two reasons. The practical one was the factory: a mirror bacterium would eat, grow and divide like any other, except that everything it produced would come out mirrored, which turns mirror drugs and mirror sugar from hand-built luxuries into something you brew in a tank. The second reason was pure curiosity. Nobody has ever built a living cell from scratch, and building one backwards would be the hardest possible proof that we understand how a cell works at all. As one of the biologists put it, if you could make a mirror cell, you could make anything.
Then they followed their own reasoning a little further.
The comforting assumption about a mirror organism has always been that it could never survive outside a laboratory. It cannot digest our food, so it starves in a world of meals it cannot eat, the way you would starve on mirrored bread.
That assumption is wrong, and everything follows from it being wrong.
Plenty of what a bacterium needs has no handedness to get wrong. Carbon dioxide, nitrogen, phosphate and glycerol, which is abundant in soil and in living tissue, are all symmetrical, so a mirror bacterium could live on them quite comfortably. Nothing could return the favour. Anything trying to eat it would be reaching in with ordinary enzymes and finding no grip, for exactly the reason the mirror sugar has no calories.
So the exchange runs one way. It could eat our world, and our world could not eat it.
Everything else that keeps bacteria in check has the same problem. Your immune system identifies invaders by their shape, and so does a plant's and an insect's. In the wild, bacterial populations are mostly held down by phages, the viruses that hunt them, and a teaspoon of seawater holds tens of millions of those. All of it is cut for the opposite handedness.
None of which makes such a thing unkillable, and the report is careful about that. A few antibiotics have no handedness and would work normally, mirror versions of the others could be manufactured, and a person with a mirror infection could probably be treated.
The trouble is everything that is not a person. Antibiotics generally work alongside an immune response rather than instead of one, and the immune response is the part that fails here. There is also no version of this where you treat a forest, or a wheat field, or the bacteria in topsoil that everything above it depends on.
The people who worked all this out were the people building it. Kate Adamala, the biochemist at the University of Minnesota who had taken the money to make a mirror cell, has described her change of mind as slow rather than sudden, and as something she arrived at herself. "It wasn't like someone came to me and said: 'You must not do it, because it will kill everyone,'" she told Noema. "It was very gradual."
In December 2024 she and thirty-seven colleagues, two of them Nobel laureates, published a paper in Science asking the world not to build what she had been funded to build. They attached a technical report of nearly three hundred pages and asked their own field to find the error in it. One of her co-authors said afterwards that they had been hoping to be proved wrong, which would have been good news for everybody, and that nobody had managed it.
On the Radar
Mirror drugs are not what anyone wants banned. A molecule cannot make copies of itself, so mirror sugars, mirror medicines and mirror enzymes that break down plastics carry no risk of spreading. The line being proposed sits at anything that can reproduce.
One machine decides the timeline. Every cell contains a ribosome, which reads genetic instructions and builds proteins to order. A mirrored one would be the first thing capable of mass-producing mirror molecules, which makes it simultaneously the commercial prize and the last real obstacle before a mirror cell is possible. The laboratory furthest along has been at it for about a decade and says it is still years away. Most estimates put a full mirror organism ten to thirty years out.
There is no law against any of this anywhere. In March the UN Secretary-General's science advisers published a brief concluding that mirror life could pose a catastrophic threat to humanity, and calling for red lines to be agreed before it becomes possible. UNESCO has recommended a global moratorium. Neither is binding, and no country has legislated. The Carnegie Endowment is now convening an international working group to turn the scientific agreement into something a government could enforce.
The dilemma of mirror biology comes down to a single phrase: nothing alive can take it apart.
At the scale of a individual drug molecule, that sentence is a medical miracle currently extending the lives of cancer patients. At the scale of an organism that makes copies of itself, that exact same sentence becomes an existential threat.
The remarkable thing about this debate is the timeline. The safety rules for genetic engineering were written after modified crops were already growing in fields, and the first gene edited humans were born before the world knew the experiment was happening. Arguing over safety guidelines a decade before the technology exists is unprecedented.
Whether the scientific consensus holds remains an open question. For now, the agreement costs nothing because nobody has the capability to build a mirror cell yet. But the financial incentive sits there in plain sight, hidden inside a forty year old patent for a perfect zero calorie sugar that nobody can afford to brew.