
Mirror life - ZeljkoS
https://en.wikipedia.org/wiki/Mirror_life
======
JetSetWilly
> Mirror life presents potential dangers. For example, a chiral-mirror version
> of cyanobacteria, which only needs achiral nutrients and light for
> photosynthesis, could take over Earth's ecosystem due to lack of natural
> enemies, disturbing the bottom of the food chain by producing mirror
> versions of the required sugars. Some bacteria can digest L-glucose;
> exceptions like this would give some rare lifeforms an unanticipated
> advantage

Does this have "great filter" implications? If it confers such a huge
advantage for a prokaryote to have the opposite chirality, then it must be
very unlikely for prokaryotes to evolve from scratch, as if it wasn't then
something would have evolved to take advantage of this. It means that "the
evolution of a simple prokaryote" has definitely only happened once.

~~~
adrianN
I find it pretty unlikely that nothing would evolve to eat the mirror
bacteria.

edit: it might take some time though. Wood was indigestible for a long time,
giving us coal deposits.

~~~
gilleain
Indeed, the premise is just wrong. It's not as if organisms cannot process
biomolecules of the other handedness. There are enzymes called 'epimerases'
and 'racemases'
([https://en.wikipedia.org/wiki/Epimerase_and_racemase](https://en.wikipedia.org/wiki/Epimerase_and_racemase))
that convert stereocenters.

While it's true that a mirror cell wall would be a barrier to being broken
down, there's nothing that would fundamentally stop the evolution of a
suitable degradation machinery for it.

------
crazygringo
> _The reverse sugars circulating in the chiral organism 's body would be
> indigestible as far as normal bacteria are concerned, so any bacterium
> entering a chiral organism would simply starve to death._

Interesting, this has been considered as a diet alternative but too expensive
so far:

> _L-Glucose was once proposed as a low-calorie sweetener and it is suitable
> for patients with diabetes mellitus, but it was never marketed due to
> excessive manufacturing costs._ [1]

[1]
[https://en.wikipedia.org/wiki/L-Glucose](https://en.wikipedia.org/wiki/L-Glucose)

------
jetrink
"How would you like to live in Looking-glass House, Kitty? I wonder if they'd
give you milk in there? Perhaps Looking-glass milk isn't good to drink."

Through the Looking Glass, by Lewis Carroll

~~~
nradov
Ironically we now know that regular cow milk isn't good for cats to drink.

------
jamiethompson
These mirror organisms would need a plethora of mirror microbes created for
them if they were to be able to do things such as digest food.

It would stand to reason then that some of these mirror good microbes would
eventually evolve to become mirror bad microbes?

------
Sephr
A mirrored chirality human is a major plot point of Daniel Suarez' "Change
Agent" book.[1][2] It has interesting use in the story as mirrored chirality
gives the character the ability to be immune to many toxins that would
normally harm humans.

[1]:
[https://en.wikipedia.org/wiki/Chemical_chirality_in_popular_...](https://en.wikipedia.org/wiki/Chemical_chirality_in_popular_fiction#Books)

[2]: [http://daniel-suarez.com/changeagentsynopsis.html](http://daniel-
suarez.com/changeagentsynopsis.html)

~~~
s_kilk
It's also a minor background detail in Mass Effect. If I recall correctly,
Turian chirality is opposite that of humans, their food is poison to humans
and vice versa, etc.

~~~
pavel_lishin
Quarians too, I believe.

------
Aardwolf
> In this way, the creation of an Earth ecosystem without microbial diseases
> might be possible

I'm not a microbiologist at all, but I don't think so. If big organisms can be
mirrored, so will microbes. You need various good bacteria so already have to
mirror those. If you've got the mirrored organisms with mirrored DNA and RNA,
it's pretty certain virii and bacteria will form from it at some point.

On another note, it's a shame we don't have a 4th dimension that we can rotate
ourselves through to mirror ourselves, that would be interesting!

~~~
kyberias
In principle you're right but that "at some point" is expected to be in the
scale of millions of years. At least it would be very unlikely.

This chiral world would give protection for all organisms to all the current
pathogenic microbes. Many would have to evolve from scratch.

~~~
otakucode
Any distinction between 'pathogenic' and 'normal' microbes is necessarily
filled with holes, and easily crossed.

------
otakucode
>In this way, the creation of an Earth ecosystem without microbial diseases
might be possible.

No. This is wrong on two fronts. First, there would be new diseases which are
of the opposite chirality, obviously. There is no such thing as a real
objective definition of 'disease'. There are only patterns which successfully
reproduce themselves and those which do not. But whatever sort of environment
constructed will essentially create its own diseases, which will infect and
interfere with what we intend to create. Successful systems breed parasites.
That's a truism in microbiology.

Secondly, a microbe-free world would kill us. There are more bacterial cells
in our body than there are cells with our own DNA. Our understanding of the
importance of our microbiology to our lives is pretty meager, but it's enough
to know that 'clean room' living would be nightmarish in the best case, but
more likely just lethal. And if your intent is to only allow in the 'good'
bacteria and viruses and funguses... that line doesn't really exist. Biology
is too messy to enable those sorts of distinctions, really.

Creating a 'mirror life' world might be pretty neat, but I don't think the
benefit would be from eliminating microbial interference in our precious
bodily fluids.

------
ocfnash
I believe it is possible that our universe is not orientable, and so there may
exist closed paths which, if followed, reverse orientation upon returning to
the starting point. If you were right-handed and traversed such a loop, you
would now be left-handed relative to everyone else, everyone would agree your
heart was on the "right" side of your body etc.

In fact even Atiyah touches on this idea (though without speculating that it
might be a property of our universe). In Mind, Matter and Mathematics, he
says:

"When I was a student in Cambridge our mathematical society invited a
distinguished professor of philosophy, C.D. Broad, to give us an evening
lecture. He chose to talk on a problem which had much exercised Kant, the
difference between right-handed gloves and left-handed gloves. After the
lecture, over dinner, I diffidently suggested to Broad that, since Kant’s
time, we mathematicians had a much better understanding of “handedness”, or
chirality as scientists call it. We could even envisage a universe in which a
left-handed glove could wander around to distant regions and return to fit
your right-hand. "

~~~
paulrouget
I think left and right could not just be swapped seamlessly. Radioactive decay
(beta) would behave differently. See Wu's experiment and parity violation.

~~~
ocfnash
Great point, I agree!

It seems to me that the statement that Wu's experiment holds globally is
equivalent to the statement that the universe has an orientation so I now tend
to think the universe does not admit one of these orientation-reversing loops.

At first I was surprised that we could apparently draw a global conclusion
based on local observations but I've mostly convinced myself now based on the
following analogy (which I hope is not misleading).

Imagine we live in a two-dimensional universe and we want to know whether or
not it is orientable. E.g., do we live on the surface of a torus or on the
surface of a Klein bottle? We have defined a local orientation in the
topologically-trivial patch where we live and so are used to speaking of
"left-handed" and "right-handed" gloves. The question of whether these words
are globally meaningful is exactly the question of whether our universe is
orientable.

One day we learn about "colour" and are stunned to discover that all left-
handed gloves are red and all right-handed gloves are blue. It seems very
unlikely to us that red somehow transitions into blue as we traverse a loop
and so we conclude we must live in an orientable universe.

~~~
skinner_
> It seems to me that the statement that Wu's experiment holds globally is
> equivalent to the statement that the universe has an orientation so I now
> tend to think the universe does not admit one of these orientation-reversing
> loops.

Nice! I tried to play around with this. There's the
[https://en.wikipedia.org/wiki/Gold_universe](https://en.wikipedia.org/wiki/Gold_universe)
where two inhabitants can honestly disagree about the direction of time. (And
the interactions between the two are hilarious.) Can we have a version where
one can go far away and come back time-reversed? Or is that excluded by CT=P
symmetry breaking? It sounds like it, but it's confusing.

~~~
ocfnash
Thanks.

With regard to:

> Can we have a version where one can go far away and come back time-reversed?
> Or is that excluded by CT=P symmetry breaking?

I don't know. Having mulled these thoughts further after writing the above I'm
now more cautious about guessing. Specifically it seems to me that
electromagetic charge, weak isospin, isospin etc. are all only globally well-
defined provided we have an orientation of spacetime. So it seems to me that
if spacetime is not orientable then there's no guarantee that if we send an
instance of Wu's experiment off in a spacecraft on a hypothetical orientation-
reversing loop then the apparatus will arrive back at earth unchanged: perhaps
its electrons are all now positrons etc.

My analogy with the coloured gloves does not permit such a phenomenon because
colour is manifestly well-defined. I could make it more elaborate to account
for this (e.g., replacing colour with a clockwise/anti-clockwise concept) but
I no longer find it useful.

In summary: I revert to my original "no opinion" point of view.

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peter_d_sherman
Fascinating! (Disclaimer: I am not a biologist or gene scientist.) This is
sort of like the anti-matter concept in Physics, but applied to DNA and other
living structures. Again, fascinating! This leads to another question, which
is does light have chirality too? What about other waves in the
electromagnetic spectrum? Does chirality affect a plant's ability to process
sunlight? Is there a reverse-chirality version of sunlight? Oh, the questions
and the possibilities! Great link for Hacker News!

~~~
type0
I don't think this applies to quantum phenomena in that sense, light can have
the so called spin but the concept is different. You can read about the
interaction of such light with chiral molecules here:
[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5247477/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5247477/)

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pavel_lishin
Wasn't this fairly close to the premise in Peter Watts' Rifters series?

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timothycubed
This was used as a plot point in Neal Stephenson's novel 'Anathem'.

