Recently the scientific community has been wondering about the risks associated with “Mirror bacteria”, i.e. synthetic bacterial forms made up of identical molecules, but mirroring those present in nature. It should be emphasized that, currently, these bacteria do not exist and therefore it is improper to give an exact definition, but in the future they could be synthesized with bioengineering techniques. After all, biomolecules mirrormirroring those present in nature, such as enzymes or nucleic acids (DNA or RNA), have already been produced in the laboratory. From here to create entire mirror microorganisms compared to living bacteria, the road is still long, but the conditions for their future synthesis are there. The concern is such that it has induced a group of 38 internationally renowned scientists, including some Nobel Prize winners, to publish the December 12, 2024 in the prestigious magazine Sciencean appeal to ask that the experimentation on the synthesis of mirror bacteria be stopped in time, given their potential danger or at least that the consequences be evaluated. As with other biotechnological applications, mirror bacteria could represent one new therapeutic frontier for many chronic diseases and have other important applications, but at the same time they could generate harmful effects not only on humans, but on all other living species. The risk considered highest is that, not existing in nature, they may be able to evade the immune system of victims, thus generating infections that are difficult to treat or have very serious consequences.
What is a mirror molecule: the chirality of molecules
All molecules in nature have their own structure and a certain orientation in space and it is precisely theirs three-dimensional shape to determine many of their properties. Some organic molecules have a asymmetric structure which makes them not superimposable on their mirror image: these molecules are called chiral. To better understand this concept it is possible to use a very common example, that of hands: if we observe our hands we see that the right hand is the same as the left, if we place them one in front of the other, but they are not superimposable.
Chiral molecules exist in two different forms called enantiomers (right-handed, R and left-handed, L) which are not superimposable and have very different properties. For example, limonene, the molecule that gives the aroma to citrus fruits, is chiral and in the left-handed conformation it generates the aroma of lemon, in the right-handed conformation the aroma of orange.
The most important biomolecules of living systems, such as DNA, RNA, amino acids or proteins are not only chiral, but in nature they are found in only one of the two conformations, DNA, for example, is a right-handed helix and exists only in this form. It’s a bit as if in nature there were only right hands and not left hands. There conformation it is essential for functions such as protein synthesis, enzyme activation, immune response and more.
For some years, biotechnologies have been experimenting with the creation in the laboratory of artificial biomolecules with inverse chirality compared to natural ones (for example, a left-handed RNA) and are finding numerous applications in long-lasting therapies. Even a large number of active ingredients contained in drugs are chiral molecules and the two right-handed and left-handed forms have, in some cases, different efficacy or even opposite effects. A very famous case is that of thalidomide, a very well-known sedative: one of the two enantiomers of the molecule is effective, the other is teratogenic (i.e. causes damage to the fetus if taken by pregnant women). The same thing happens for the very common ibuprofen which is effective only in one of the two chiral synthetic forms.
What could happen if mirror bacteria were synthesized
Just as today pharmacology makes use of synthetic mirror molecules, tomorrow entire microorganisms capable of producing enzymes with inverse chirality and effective for the treatment of rare diseases could be “created” in the laboratory. The main problem of these bacteria and the concern that is generated is that we could say that the whole world we live in is chiral and biological interactions have evolved between molecules with specific chirality.
Obviously the circulation of an entirely new and non-naturally occurring organism could have an uncontrollable effect on how it might react with the rest of the world. For example, one of the most feared effects is that could not be recognized by the immune system of living organisms and therefore not find any obstacle to new infections. Furthermore, these bacteria would be antibiotic-resistant, because the drugs are also chiral, and capable of persisting for a long time in an external environment without finding pharmacological “enemies” or bacteriophage predators (which feed on bacteria).
It is difficult to predict possible “scenarios” today something that doesn’t exist yetbut as with other synthetic substances it would be risky improper use accidental or deliberate, this is why the appeal of scientists to face this new hypothetical challenge through collaboration between researchers, governments and pharmaceutical industries to identify useful but highly biosafe testing strategies.
