Our body is a small ecosystem: billions of microbes, bacteria and viruses coexist with us every day, helping us to digest, defend ourselves from infections and even keep our mood stable.
Yet, in this teeming life, scientists have found something completely new: tiny circular RNA molecules that resemble nothing previously known.
These mysterious fragments are not viruses, nor bacteria, nor plant viroids. I’m a little bit of everything and a little bit of nothing. Scholars have named them “obelisks”, perhaps due to their elongated and compact shape, like a thin column of genetic information. The discovery, published in the journal Cellhas left the scientific community speechless: in the literal sense of the term, given that it is precisely in the mouth that these invisible beings seem most numerous.
Tiny, circular and intelligent
Obelisks are small RNA molecules about a thousand genetic bases long. When they are “read” and modeled on the computer, they take on a stick or command stick shape, a repetitive and symmetrical structure that resembles certain plant pathogens known as viroids.
But there is a detail that makes them even more interesting: some obelisks encode a protein, renamed with a name worthy of a fantasy novel – Oblin. This feature clearly distinguishes them from viroids, which do not encode proteins. It is as if these new entities lived halfway between a virus and a cell, in a gray area of biology that we had previously ignored.
Scientists identified them not with a microscope, but through artificial intelligence algorithms applied to huge databases of RNA taken from human samples. They looked for two signals: the “junction” that reveals a circular molecule and a stick-like fold predicted by RNA folding models. When both conditions appeared together, there was the obelisk.
And do you know where the greatest number of these strange entities were hiding? In the oral microbiome, the invisible world that inhabits our mouth, between saliva and bacteria such as Streptococcus sanguinis.
Obelisks live in the mouth and perhaps reproduce on their own
Analyzes show that obelisks are not a passing anomaly: they can remain stable in a person’s mouth for months, as if they found their ideal habitat there.
And some bring a detail that seems straight out of a science fiction film: a “ribozyme-headed hammer”, a sequence capable of cutting and mending itself. Simply put, a piece of RNA that replicates itself, without the need for external enzymes or proteins. A primitive and ingenious system which, after all, recalls the way in which the first molecules of life on Earth could have formed.
Not all obelisks have this “integrated tool”, but their constant presence in oral bacteria suggests a symbiotic relationship: they do not seem to cause diseases, but coexist peacefully with us and with our bacterial flora.
The obelisks challenge our definitions. They are not viruses, they are not bacteria, they are not even organisms in the classical sense of the term. But they are alive, or at least act like one.
They can replicate, adapt, interact with bacterial cells and resist over time.
In short, a new category of biological entities so far invisible to our instruments.
Experts haven’t yet figured out whether these micro-RNAs affect human health, but their discovery opens a fascinating door: Our body could be a much more crowded and complex house than we imagined.
You might also be interested in:
