Last week I ran across an article in the journal Science about our capacity for creating "mirror life," and the risks thereof. I considered addressing the topic here, but after some thought concluded that the human race has more pressing things to worry about at the moment, such as climate change, global pandemics, terrorism, environmental collapse, and Donald Trump opening the Seventh Seal of the Apocalypse because he thought it was a can of Pepsi, so I decided against it.
Since then I've been sent the article (or various summaries and commentaries) four times, along with the questions "can you tell me more about this?" and "should I be freaking out right now?" So I guess there's enough interest (and concern) over this that it's worth a post.
The answer to the second question, at least, is "No, not yet;" and as for the first, here goes.
The issue has to do with a property of a great many organic molecules called chirality. Chirality is like the handedness of a pair of gloves; no matter how you flip or turn a left-handed glove, it's not going to fit on your right hand. It's made of the same parts, but put together in such a way that it can't be rotated or translated to coincide with its opposite. Pairs of molecules like that are called enantiomers or optical isomers (the latter because crystals made of them rotate polarized light in opposite directions).
The key point here is that on Earth, living things generally can only synthesize and metabolize one form of chiral molecules; our amino acids are all left-handed, while our sugars (including the ones in the backbones of DNA and RNA) are right-handed. Given a diet of food made of right-handed amino acids and left-handed sugars, we'd probably not notice a difference in taste or texture -- but since our enzymes are all evolved to deal with a particular handedness, the food wouldn't be metabolizable.
In short, we'd starve to death.
The article in Science deals with the fact that biochemists have been working to find out if it's possible to create "mirror life" -- organisms constructed of molecules with the opposite handedness as our own. And this is what has some people concerned. The authors write:
Driven by curiosity and plausible applications, some researchers had begun work toward creating lifeforms composed entirely of mirror-image biological molecules. Such mirror organisms would constitute a radical departure from known life, and their creation warrants careful consideration. The capability to create mirror life is likely at least a decade away and would require large investments and major technical advances; we thus have an opportunity to consider and preempt risks before they are realized. Here, we draw on an in-depth analysis of current technical barriers, how they might be eroded by technological progress, and what we deem to be unprecedented and largely overlooked risks. We call for broader discussion among the global research community, policy-makers, research funders, industry, civil society, and the public to chart an appropriate path forward.
The main concern is that if these mirror organisms were somehow to escape from the lab, we wouldn't have much of a way to fight back. Both antibodies and antibiotics are chiral as well, and likely wouldn't recognize and bind to organisms whose cell surfaces were made of molecules with the opposite handedness. Any of these synthetic organisms that did turn out to be pathogenic would require a whole different suite of medications, and our own bodily defenses would likely be relatively useless against them.
But.
Here's the thing. If the scientists do succeed in creating mirror life, and it does escape, the most likely result would be... nothing. Mirror life would itself need food, and of the proper handedness for its own enzymes; and given that everything in the environment has the same left-handed amino acids and right-handed sugars that we do, these synthetic life forms would have nothing to eat. The only possible problem would be if the scientists created a mirror autotroph -- something capable of synthesizing its own nutrients, like cyanobacteria, algae, or plants. Then, it could be a problem, from the standpoint that like exotic invasives, it would have no natural predators and might outcompete other organisms in its environment.
The other concern, though, is the "life finds a way" thing. A mutation allowing one of these synthetic organisms to metabolize proteins or sugars of the opposite handedness from their own (or both of them) would be at a distinct advantage; if we created one of those, and it escaped, we might well be fucked. The thing is, from what we know of biochemistry, that's an extremely rare adaptation. I only know of one organism -- a rather obscure plant pathogen called Burkholderia caryophyllii -- that has an enzyme called D-threo-aldose 1-dehydrogenase that allows it to oxidize left-handed glucose.
But unless you're a carnation, Burkholderia isn't a threat.
So that's an awful lot of ifs. Thus my response that you don't have anything pressing to worry about from this research.
Now, mind you, I'm all for being careful, and I mean no criticisms of the scientists who are advising cautious consideration. We have a rather abysmal track record of launching into stuff without thinking about the consequences. But as far as whether we ordinary laypeople need to be worried about some synthetic mirror-image pathogen attacking next Tuesday and reducing us all to little quivering blobs of goo, I'd say no.
On the other hand, I'm the guy who told his AP Biology students in January of 1997 that "adult tissue cloning is at least ten years away," exactly one month before the announcement about Dolly the Sheep. So maybe any predictions I make should be taken with a grain of salt.
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