[ExI] thinking about the unthinkable

[John Clark]

On Mon, Aug 31, 2026 at 10:43 AM <spike at rainier66.com> wrote:


*> I am suggesting mirror life could not survive in the presence of
> non-mirror life. *



*I asked GPT the following question: *


 *ME:Somebody told me that mirror life could not survive in the presence of
non-mirror life, but I think nothing could eat a mirror bacteria and there
must be some non-Chiral chemicals it could use as food. Who is right?*

*GPT: "Y*our intuition is basically right. *The statement “mirror life
could not survive in the presence of ordinary life” is too strong.* In
fact, the concern researchers have been discussing is almost the opposite:
a sufficiently robust mirror bacterium might have *fewer natural predators
and competitors* than ordinary bacteria.

There are two separate questions here.
1. Could ordinary organisms eat a mirror bacterium?

Probably *very poorly, if at all*.

Suppose a normal bacterium is eaten by another bacterium. The predator uses
enzymes—proteases, nucleases, etc.—that have evolved to recognize ordinary
biological molecules. A mirror bacterium would have the opposite chirality:

   - ordinary proteins → mostly *L-amino acids*
   - mirror proteins → *D-amino acids*
   - ordinary DNA/RNA → *D-sugars*
   - mirror DNA/RNA → *L-sugars*

The difference is rather like trying to put your *left hand into a glove
designed specifically for your right hand*. The atoms are the same, but the
three-dimensional geometry is wrong.

 Consequently, ordinary enzymes generally cannot digest mirror proteins or
nucleic acids efficiently. Likewise, ordinary viruses and many other
biological recognition systems would have difficulty interacting with
mirror cells.

So your basic idea—*“nothing could eat it”*—is directionally correct,
although “nothing” is too absolute. There are chemical and physical
processes that don't care about chirality, and there could potentially be
specially adapted natural organisms.
2. But what would the mirror bacterium eat?

This is where your second point is particularly important.

Not every useful nutrient is chiral. Some relatively simple molecules are
*achiral*, meaning they have no left/right version. For example, glycerol
and butyric acid are examples of achiral compounds that could potentially
be metabolized by either type of biology.

And the 2026 UK government assessment specifically notes that *some
substrates in the body are achiral and could support mirror bacterial
growth*. It also says that mirror organisms might potentially evolve or be
engineered to use nutrients of the opposite chirality.

There's an important subtlety here, though:

*A mirror bacterium couldn't simply eat an ordinary glucose molecule and
use its ordinary enzymes to metabolize it.* Its enzymes would have the
wrong handedness. But a mirror organism could have its own mirror metabolic
machinery for processing whatever substrates are chemically accessible to
it.

And if somebody engineered the organism appropriately, the range of usable
nutrients could potentially be considerably larger.
The really interesting ecological consequence

Put those two facts together:

*Ordinary bacterium:*

Food → ordinary enzymes → growth
↓
Can be eaten by lots of organisms
Can be attacked by viruses
Can be killed by immune systems
Competes with enormous existing microbial ecosystems

*Mirror bacterium:*

Achiral/compatible nutrients → mirror enzymes → growth
↓
Natural predators may not recognize it
Natural viruses may not infect it
Natural enzymes may not digest it
Natural immune systems may have difficulty recognizing it

That is why the possibility has attracted serious biosafety attention. The
concern isn't that mirror bacteria would necessarily starve in our
biosphere; *it's that they might find enough resources while being
unusually difficult for the existing biosphere to control.* The UK's
assessment explicitly identifies lack of natural predation as a potential
problem and says photosynthetic mirror organisms could be particularly
concerning because they wouldn't need an external food supply.

There is, however, a big caveat: *mirror life does not currently exist.* A
self-replicating mirror bacterium has not been created, and constructing
one remains a formidable scientific problem.

So I'd put it this way:

*Your friend has the ecological relationship backwards.* Chirality would
make it difficult for ordinary organisms to exploit or attack mirror life,
but it does not imply that mirror life couldn't obtain nutrients from the
ordinary world. Achiral nutrients provide one possible bridge, and
engineered or otherwise suitable metabolism could provide others.

And there's an interesting deeper question hiding here: *how much of
Earth's biomass is actually accessible to a mirror organism?* That's
considerably more complicated than simply saying “it can eat achiral
chemicals,” because a bacterium needs carbon, nitrogen, phosphorus, sulfur,
trace elements, energy sources, etc., and each one has to be incorporated
through a compatible biochemical pathway. That's where the question becomes
a genuinely fascinating ecological problem."
*John K Clark    See what's on my list at  Extropolis
<https://groups.google.com/g/extropolis>*


*4dc*
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