Scientists have discovered a new type of living organism, called an “obelisk”, in the microbiome of the mouth and intestines.
- Researchers have discovered a new category of infectious agents.
- Called obelisks, they are present in the oral and intestinal microbiome.
- Currently, we do not know their impact on bacteria.
This is an unexpected discovery. Researchers at Stanford University have identified a new type of infectious agent present in the microbiome of the mouth and intestines. Close but different from viruses, these living organisms have been called “obelisks”. In the specialist journal bioRvixscientists say more about their identification.
Microbiome: unclassifiable infectious agents
“Obelisks comprise a class of diverse RNAs that have colonized and gone unnoticed in human microbiomes“, write the researchers in their scientific article, which has not yet been peer-reviewed. The name of these new agents comes from their shape, marked by highly symmetrical rod-shaped structures formed by the twisted lengths of RNA.”The genetic sequences of obelisks only have around 1,000 characters (nucleotides), develop the authors of the study. In fact, this brevity is probably one of the reasons we haven’t noticed them before.” These fragments of genetic material have no structural similarity to other known biological agents. For the authors of the study, led by Ivan Zheludev, a biologist at Stanford University, this discovery could help “bridging the ancient gap between simpler genetic molecules and more complex viruses”.
Obelisks present in the oral and intestinal microbiome
The team worked on more than 5 million genetic sequences: this allowed them to identify around 30,000 different obelisks. In a specific data set, obelisks appeared in 50% of patients’ oral samples and in 7% of intestinal samples. Researchers have successfully isolated a type of host cell from the human microbiome, the bacteria Streptococcus Sanguinis, a common human oral microbe. “Although we don’t know the ‘hosts’ of the other obeliskswrite the American researchers. It is reasonable to assume that at least a fraction may be present in bacteria.”
“They are much larger than other genetic molecules that coexist inside cells”
They observe that more than half of the genetic material in these obelisks contains instructions for building proteins, called Oblins. “This ability to encode proteins makes them different from other known RNA loops called viroids, but they also do not appear to have the genes needed to make the protein shells that RNA viruses (including Covid-19) live in. when they are outside the cells, detail the authors. They are also much larger than other genetic molecules that coexist inside cells, from plants to bacteria, called plasmids, which are more commonly composed of DNA.” At the moment, researchers don’t know what impact the obelisks have on bacterial hosts, or how they might spread between cells. Future research will reveal more about these mysterious new agents.
