Mirror Life refers to the concept of creating or studying life forms that employ mirror versions of the biomolecules found in natural organisms. In conventional biology, life is based on chiral molecules with a specific orientation: for example, amino acids are predominantly levorotatory (L-forms), while sugars in nucleic acids are right-handed (D-forms). This chirality is a fundamental building block of biochemistry as we know it. Exploring mirror life challenges our understanding of the fundamentals of biology and the universality of biochemical principles, opening up questions about the possibility of alternative forms on other planets.

In all the Synthetic Biology courses I teach, I include this topic and discuss the progress made in this field. I recognise that it is one of the topics that has the greatest impact on students. The recent articles in Science and the related report on the associated risks are certainly relevant and timely. However, reading them, I can't help but feel a sense of déjà vu. In 1969, Jon Beckwith announced at a press conference the first isolation of a gene from DNA, while warning society about the potential dangers of manipulating genetic material, a then nascent field. In my talks, I often present Beckwith as an emblematic example of what I call the ‘firefighter-pyromaniac paradox’: someone who lights a fire, warns about the resulting problem, and then sets himself up as the fixer, drawing attention to his field.

Perhaps something similar is now happening with synthetic biology in general, and mirror life in particular. On the one hand, the possibility of creating such life inspires awe and fascination; on the other, it raises concerns about potential problems. In a sense, scientists create the challenge, then warn of its risks, and finally propose solutions under their leadership. Without adequate pedagogy, it is legitimate to question why this quest was initiated in the first place.

My perspective on the issue and my reaction to the Science article (plus the report) includes several considerations:

1. Scientific curiosity. From this point of view, exploring alternative life forms with opposite chirality is fascinating. However, we must be realistic: although we have made progress in creating mirror molecules and macromolecules, we are far from building a functional living cell from scratch, even using conventional chirality. I believe we are at least 10-20 years away.
2. Beneficial applications. The Science article focuses on the risks, but it is crucial to highlight the possible advantages as well. Focusing the narrative solely on the dangers may alienate the public, as scientific curiosity alone does not justify venturing into such uncharted and potentially dangerous territory.
3. Governance and oversight. I am concerned that the panel charged with drafting this report is composed almost exclusively of US (or US-orbiting) scientists, with little international representation. Given that the risks and benefits of this research have global implications, it is essential to include actors from diverse regions and contexts in the debate.

In my case, after years of developing genetic technologies to enhance the biodegradative capacity of environmental bacteria, I have found a general rejection of the idea of using laboratory-engineered organisms for bioremediation. This is even when their use would be crucial in the context of climate change.

I have therefore worked for years to reframe the debate on genetically modified organisms (GMOs), promoting an approach that does not present them as tools of domination over nature, but as a dialogue with the biological world: a partnership that leads to mutual benefits. This approach can facilitate a more positive and acceptable perception, framing research as a search for a shared purpose. In this sense, I insist on highlighting the possible beneficial applications of mirror life.

In any case, as this concept represents a step into the unknown, we must approach it with caution, learning from past mistakes in communicating innovations to the public. The stumbles of the pioneers of genetic engineering provoked a significant public backlash, and we must do our best to avoid repeating those experiences.

It is a very interesting reflection that includes some experts with decades of experience in working with this problem.

Certainly, the generation of asymmetric life raises fascinating questions: Why was this asymmetry chosen? What is the degree of orthogonality between lives that are mirror images of each other?

It is possible that life with the new symmetry has the ability to escape the main defence mechanisms and may be a danger. Especially since bacteria can grow from non-chiral elements.

It is true that, although it seems so far away to have a specular whole bacterium, perhaps it is not so far away to have specular components in bacteria.

There is an intriguing new world on the other side of the looking glass whose properties we are only beginning to glimpse and about which we should be very cautious. This call for a halt to experimentation on future mirror cells follows a tradition of similar calls on other biotechnologies with potential real-world impact: from the Asilomar conference on recombinant DNA, to the recent editorial on controlling the construction of new proteins designed by AI techniques, signed by George Church and David Baker (recently awarded the Nobel prize precisely for the construction of new proteins).

The current debate on mirror cells adds to these precedents also promoted by leading scientists, far from sensationalism - nothing like the AI debate - and reveals the pressure of the accelerating pace of scientific innovation when the distance between research and application is dramatically shortened, together with the great difficulty of estimating its impact in the real world, for example, how a new variant of an infectious disease, say covid, would spread.

In this case, early publications describe steps to create proteins with D-amino acids, mirror copies of natural proteins made of L-amino acids. These proteins can have special properties such as being more resistant to degradation, a property that can be useful in industrial applications but can also make these proteins very difficult to destroy by systems operating in the real world, such as the immune system or proteolytic enzymes, with the consequent danger if they were to operate outside the laboratory.

Beyond these new proteins, the next challenge must be to synthesise complete cells with a mirror DNA/genome (natural DNA is D-conformational). These synthetic cells might be able to reproduce and evolve, creating a symmetrical world that could come to compete for resources with our ‘real’ world. While this possibility is by no means immediate, it does represent a danger of sufficient magnitude to stop these experiments in the opinion of the authors of this statement.

This article is yet another example of the need to act responsibly with respect to the possible innovations that may result from scientific advances. At times we scientists have not acted in a coordinated and publicly visible way (usually not for lack of will) in anticipating and avoiding the risks of the applications that may arise from science, the clearest example being the development of nuclear weapons in the middle of the 20th century. Since then, the scientific community has acted more stringently, the best example being the 1975 Asilomar conference, when the scientific community self-imposed restrictions on the use of recombinant DNA. Since then, such actions have been attempted periodically, with varying degrees of success, in areas such as synthetic biology, human cloning, and artificial intelligence.

In the specific case of specular biology mentioned in the article, it is certainly still a mystery why life on this planet has chosen a particular symmetry in its fundamental molecules, and it is possible to think that another form of life could develop using the opposite symmetry (see for example the episode “Mirror, mirror” from the 2nd season of the original Star Trek series, 1967). In principle this new life form could interact little with the existing one (for example it could be that mirror pathogens would not be effective in invading common hosts), but not being sure it is very convenient to be forewarned and establish protocols that prevent harmful situations in the future. Not designing this type of life is not an option if we want to continue to understand the universe better (to improve the health of our planet and its residents), but not thinking responsibly about the consequences is not an option either.