Amazement at the discovery of a completely new type of life in the human digestive system

In the “jungle of microbes” that live inside us, scientists were amazed when they came across what could be a completely new class of virus-like objects.

“It’s crazy,” University of North Carolina cell biologist Mark Peifer, who was not involved in the study, told Science magazine. “The more we look, the more crazy things we see.”

These mysterious bits of genetic material don’t even have detectable sequencesto known structural similaritiess from other biological agents.

That’s why biologist Ivan Zheludev of Stanford University and his colleagues argue that their strange discovery may not involve viruses at all, but a group completely new entities which may help bridge the long-standing gap between simpler genetic molecules and more complex viruses.

“The ‘obelisks’ (as they called the unknown entities) comprise a class of different RNAs that they colonized and went unnoticed in human and global microbiomes,” the researchers said in the study published on bioRxiv.

The genetic sequences of obelisks, which get their name from the highly symmetrical rod-shaped structures formed by their twisted stretches of RNA, “They are about 1,000 nucleotides in size.”.

Indeed, “this characteristic “That’s probably one of the reasons we didn’t notice them before,” they say.

In a study that has not yet been peer-reviewed, Zheludev and his team examined 5.4 million published genetic sequence datasets and They identified nearly 30,000 different obelisks. They appeared in about 10% of the human microbiomes examined by the team.

In one dataset, obelisks appeared in 50%. of oral patient samples. Furthermore, different types of obelisks appear to be present in different areas of our body.

“This supports the idea of ​​obelisks they could include settlers of these human microbiomes,” the researchers explain.

They managed to isolate a type of host cell from our microbiome, the bacterium Streptococcus sanguinis, a common microbe in the human mouth. The Obelisk had these microbes a loop 1,137 nucleotides long.

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

“They all appear to include codes for a new class of proteins,” the researchers say They called Oblins.

It appears that the instructions for building these proteins take up at least half of the Obelisks’ genetic material. Because these proteins are so similar in all obelisks, the researchers suspect they may be involved. in the entity replication process.

This ability to code proteins It differentiates them from other known RNA loops called viroids, but they also don’t appear to have the genes to make protein coats that RNA viruses (including COVID-19) live on when they’re outside cells. .

Also they are significantly larger than other genetic molecules that coexist inside cells, from plants to bacteria, called plasmids, which are commonly composed of DNA.

However, Zheludev and his team were unable to identify any impact of the obelisks on their bacterial hostsnor a medium through which they could spread between cells.

“These elements could not even be of a “viral” nature. and may look more like ‘RNA plasmids,'” they concluded.

Source: Scientific Notice