“It’s crazy”: scientists discover a new type of viral life in our intestines

There are billions of microorganisms, including bacteria, but also viruses, fungi and protozoa, that exist in the human gastrointestinal tract.. However, something never seen before was reported this week in a preprint: A new type of viral life, which lives in the human mouth and intestine, has been discovered all over the world.

Scientists call them “obelisks,” which are small circular fragments of RNA (even smaller than viruses) that colonize bacteria inside the human gut and mouth. Researchers have found nearly 30,000 different obelisks, in samples from around the world. while exploring over 5 million published genetic sequence datasets.

Other scientists are delighted with the appearance of the obelisks. “It’s crazy,” he said. Science Mark Peifer, cellular and developmental biologist at the University of North Carolina at Chapel Hill. “The more we look, the crazier things we see.”

The work, which was published on the preprint server bioRxiv on January 21 and has not been peer-reviewed, suggests that the obelisks are folded into rod-like structures. Regarding the structure They are unlike any other known biological agents and form their own distinct phylogenetic group with no detectable sequence.

They are only about 1,000 bases long. Actually, This brevity is probably one of the reasons why they had not been noticed before.

Although the obelisks have the same shape as many others »viroids “, structures made of RNA similar to viruses but much smaller, their genetic sequences are very different, implying that they form a distinct but related group. In any case, more work is needed to see how different the viroid obelisks are.

This is why Ivan Zheludev, a biologist at Stanford University, and his colleagues say that Their strange discovery may not even be viral in nature, but rather a whole new group of entities. this can help bridge the long-standing gap between the simplest genetic molecules and the most complex viruses. They might look more like RNA plasmids, the team concludes.

The research results revealed a large number of obelisks in stool samples taken from people around the world. In samples of 472 individuals, mostly from North America, The authors found that 6.6% of people carried obelisks in their gut microbiota and 53% carried them in their oral bacteria.

Because obelisks contain genes unlike any discovered so far in other organisms, “they constitute a class of diverse RNAs that have colonized and gone unnoticed in human and global microbiomes,” writes l ‘team.

It is not known whether this new agent could affect human health. The answer may lie in a common bacteria found in the mouth called Streptococcus Sanguinis, in which researchers discovered a family of obelisks.

“Although we do not know the ‘hosts’ of the other obelisks”, they write Jeludev and colleagues. “It is reasonable to assume that at least a fraction may be present in bacteria.”

What we know is that all appear to include genes that encode a new class of proteins that researchers have named Oblins which researchers suspect of being involved in RNA replication.

The study is “an important milestone” because it presents the best available evidence that such elements are widespread throughout the bacterial world and not just in more complex organisms, he said. Nature molecular biologist Joan Márquez-Molins of the Swedish University of Agricultural Sciences in Uppsala, who was not involved in the work. “It’s not really something that’s sporadic or isolated within the population; This actually affects a considerable portion of the sample,” he said.