Will "mirror" bacteria consume all life?
In a new paper, The Alarm = sounded.
Yesterday, Science published the remarks of a group of concerned scientists. What has troubled them to speak out? Oh, only the end of the world.
In short: There exists in theory, and probably within the very short term possibilities of biological engineering, a “Bizarro World” model of life, alien to the current form we have on earth but also essentially a reflection of it. The current form, however, can produce almost no defense against it in a competition for survival — it has never needed to, because this form of life could never arise naturally.
If it is brought about unnaturally, even in the simplest form (bacteria), most multi-cellular life will have no practical defense to being “decomposed alive.”
While it has existed as a theoretical concept for over 30 years, it is only the recent approach of human-kind to the technical capability of “mirror” life that has caused the gravity of the problem to “sink in” with our group of Cassandras — perhaps at some point it has also been the topic of science fiction, but I am not aware of such a work. As far as I am aware it is a brand new vision of doom.
How to read this post:
The paper above, here, is a succinct summary of the problem, and accompanied by a larger review of the topic, here (pdf). If the reader wants the most well-organized short or long version of this topic, see the paper itself, and consider this post as merely a “check this out” notification.
In order not to cause the reader to look in two places for the same info, I have focused only on how I can augment their excellent summary. Subscribers should note that this post may not fit your email:
>I want to understand the basics about this “mirror” life concept:
See the first section below, which offers a graphical “explainer.”
>I want the most succinct summary of this topic:
See the paper itself (duplicate link).
>I want a graphical representation of the maximally worst possible outcome of the development of “mirror” bacteria:
See the second section below (which may receive substantial updates if readers point out problems with my representation, or contribute additional possible outcomes).
>I want reasons why this may be nothing to worry about
See the third section below.
i. Mirror life: The basic concept
Slide 1: Life is built in one “hand”
Slide 2: Some more discussion on the “logic” of Homochirality — the reader may skip past to focus on how this “default” system scales up.
Slide 3: Let us take the “half of you” example further. If a cell wants to make a protein or poly-protein out of multiples of just your left side (imagine this seen from above), what would that look like? We can imagine one copy of your left hand being linked to another copy of your left hand, and one copy of your torso being linked to another copy of your torso. Not a perfect metaphor for proteins (just a string of head-to-toes, but all left handed), but it leads up to our visualization of “mirror” life below so let’s use it.
Slide 4: Continuing this idea, we arrive at a visualization of all regular life is formed on the molecular level (many many copies of just the left half of you):
Slide 5: “Mirror” life, thus, is the theoretical assembly of an entire organism made out of the right half of you. The whole organism would be a mirror version of every existing protein and every existing R/DNA molecule of a current organism, made in a lab:
For a summary of how close we are to being technically capable of creating such an organism, and how such an organism would survive in a world that it is the “mirror” of, see the original paper (duplicate link).
ii. What is the worst-case scenario of “mirror” bacteria?
Short answer: The end of almost all multi-cellular life.
Here, I am repeating many of the concepts discussed in the paper — these concerns are the very reason the authors have issued their warning. But I believe it is useful to offer my own graphic representation of these worst-case possibilities.
The threshold for worst-case: A hardy bacteria able to propagate without consuming exogenous metabolites, e.g. “mirror E. coli”
Basically, the second-simplest level of “mirror” life that scientists might attempt to construct (after a mirror-virus, which would be harmless since it is a parasite of (non-existent) “mirror” cellular life) is sufficient to create the highest level of theoretical risk for us.
In this one case I will quote the paper:
In isolation, mirror bacteria would function identically to their natural-chirality counterparts if provided with achiral or mirror-image nutrients—and be as feeble or robust as the strain that served as their template. Genetic engineering could transform a slow-growing, specialized mirror bacterium into a mirror version of a fast-growing, generalist bacterial strain. Many bacteria, including Escherichia coli, can grow robustly in growth media without chiral nutrients; hence, mirror versions of those bacteria would do the same. Achiral nutrients are available in quantities sufficient for growth of common bacteria in a wide range of natural environments, including within potential hosts. Further genetic engineering could provide mirror bacteria with pathways needed to consume abundant chiral nutrients such as d-glucose.
Growth of mirror bacteria outside of the laboratory is therefore plausible. However, their interactions with other lifeforms would differ profoundly because of their reversed chirality.
Currently, scientists can make mirror versions of the building blocks of such a bacteria as “mirror E. coli.” Once science is able to put enough building blocks together to make any complete mirror organism, the threshold will essentially have been reached where “mirror E. coli” capable of thriving outside of the lab will also have been reached. “Mirror” bacteria will be ready to escape into our regular biological world, and multiply exponentially (as bacteria do).
How will it then affect life, as the authors say, is the question.
Will all life end?
In the worst case, our current bacterial kingdom may see many species go extinct, but the overall biomass of “regular” bacteria is not at serious long-term threat from “mirror” bacteria.
Multi-cellular life has much less reason for optimism: “Mirror” bacteria would be deprived of some adoptive advantages on their side of the coin, whereas multi-cellular life would be deprived of almost all anti-bacterial defenses on ours.
In the worst-case, the entire concept becomes all but “obsolete.”
The grim-ness of this scenario stems from the fact that multi-cellular life cannot even return, in case of such an outcome, unless one or the other of regular or “mirror” bacteria all die out.
If the “mirror” bacteria, after escaping a lab, eating much of multi-cellular life alive until most metazoan ecosystems collapse, then go on to die out, perhaps evolution can “reset” to 1-3 billion years ago. Otherwise, “regular” life (regular bacteria and a few remaining more complex organisms) will still be trapped in an “operating system” of one-handed proteins and D/RNA which has no means of evolving a means to coexist and compete against “mirror” bacteria.
iii. Is this all probably not really possible?
The scientists behind this paper would not have sounded this alarm, were it clear that a lab-created “mirror” bacteria could have no chance of thriving in our opposite-handed world.
Of course, that doesn’t mean that it is clear that it couldn’t, either. Only that, in their model of what is likely, it seems plausible that there are no intrinsic, hard limits to the fitness of “mirror” bacteria in our world.
But perhaps in fact there are. I offer my own examples:
1. One-world right-handism
In the absolute best-case, there are yet-to-be-understood reasons why an opposite-handed organism cannot truly meet the conditions of life — especially of propagation.
For example, many aspects of our one-handed world may be propagated by mere contact between distinct but nearby cells. For example, it is found that experimentally remodeled amoebas pass on “flipped” cellular architecture to progeny, despite an absence of any relevant genetic modifications (Inaki, M. Liu, J. Matsuno, K. (2016) - section 2).
One might imagine that a “mirror” organism enmeshed in a world opposite of itself, would experience a lethal “molecular pressure” of sorts, causing it to build improperly rotated cell structures of these sorts, rendering it unviable or at least unfit outside of a lab experiment.
Alternately, the biophysics of reality simply prohibit a functioning “mirror” organism for some reason.
This would in essence mean that our current, one-handed version of life is intrinsically immune to the alternate model.
2. The problem is too small or slow to matter
Next-best, even if “mirror” bacteria prove viable in the wild, and possess the ability to colonize multi-cellular organisms at a large scale, their growth rate is not high enough to cause substantial mortality — even within the paradigm where the weakest multi-cellular species lead a race to the bottom (as in my graphic). Relatedly, the long-term dangers may be the same, but the progress toward them may be so slow that humans never notice the problem as long as we are still here. It could be that instead of “years” in the timeline above, the problem plays out in eons.
3. The odds are too long (both slow and self-limiting)
Finally, perhaps “mirror” bacteria would prove to be too disadvantaged to survive — not only would their colonization of regular life be painstaking and slow, but conditions would be too harsh due to competition for resources. In this case, all releases of “mirror” bacteria would tend to die out on their own, without ever causing a noticeable disruption to our world.
This outcome seems intuitively “narrow” within the spectrum of possibilities — “mirror” bacteria are viable in the wild, but just not viable enough — which is why I have rated it second-last among the “bests.”
4. Humans heed the warning issued in yesterday’s paper
Our authors conclude with advice for a ban on mirror life research:
Unless compelling evidence emerges that mirror life would not pose extraordinary dangers, we believe that mirror bacteria and other mirror organisms, even those with engineered biocontainment measures, should not be created. We therefore recommend that research with the goal of creating mirror bacteria not be permitted, and that funders make clear that they will not support such work. Governance of a subset of enabling technologies should also be considered to ensure that anyone attempting to create mirror bacteria will continue to be hindered by multiple scientifically challenging, expensive, and time-consuming steps.
It should be obvious why I have rated “humans voluntarily refrain from destroying the world” as the worst (i.e. least robust) of “best” case outcomes in this list. It is clearly not realistic.
If you derived value from this post, please drop a few coins in your fact-barista’s tip jar.
So much time, energy and money wasted chasing dark powers and so little invested in health and fitness with humility and reverence for complexities beyond our understanding.
This fits with my personal explanation of why we haven’t found intelligent life out in the universe - eventually they get so clever that they extinct themselves!