Our bodies are home to trillions of microbes, including bacteria, viruses, fungi, and a whole host of others. Now, Stanford scientists have discovered an entirely new class of biological entities inside us, which they’ve ominously named “Obelisks.”
The microbiome we all carry around with us is so vast, we’re still regularly learning new things about its makeup and how it affects our health. New strains of bacteria or viruses are discovered in there from time to time, but it’s not often scientists discover a completely new group of entities that don’t fit any known category.
The Stanford team calls them Obelisks, thanks to their rod-like structure, and they’re kind of a cross between viruses and viroids. We’re all familiar with the former, while viroids are simpler molecules of RNA that can replicate by chopping up and reforming their genome, but don’t produce proteins and lack a protective shell. Obelisks have the basic structure of viroids, but like viruses their simple genomes do seem to code for previously unknown proteins the scientists call “obulins.”
It turns out that Obelisks are very common and surprisingly diverse. The scientists discovered almost 30,000 different types of them within microbiome samples taken from over 400 people from all around the world. They were found in about 50% of tested oral microbiome samples and 7% of gut samples. It seems they’ve eluded detection so far because they don’t look like anything else we know about.
“We find that Obelisks form their own distinct phylogenetic group with no detectable sequence or structural similarity to known biological agents,” the researchers write in the paper.
Exactly what they do in our bodies remains a mystery for now. They could help or harm their hosts, which might not be us directly but bacteria or fungi that call our bodies home. So far, the leading candidate is the Streptococcus sanguinis bacteria, which resides in dental plaque. The researchers say this easy-to-cultivate bacteria species would be the best starting point for studying Obelisks further.
The study has yet to be peer-reviewed, but it’s available as a pre-print on bioRxiv.
Source: The Conversation via Nature
