Scientists have discovered a ‘crazy’ new lifeform lurking inside our bodies. They found entirely new virus-like entities, named ‘obelisks,’ which are are circular bits of genetic material that contain one or two genes and self-organize into a rod-like shape.
Obelisks appear in half of the world’s population, but were only discovered when researchers were searching for patterns that didn’t match any known organisms in genetic libraries.
They colonize the bacteria inside the mouths and guts of humans, living inside their host for about one year, but scientists do not know how they spread.
Obelisks have genomes of loops of RNA that resemble viroids, which are viruses that infect plants, leaving experts puzzled to why they were found in human-associated bacteria.
‘It’s insane,’ Mark Peifer, a cell and developmental biologist who was not involved in the research, told Science. ‘The more we look, the more crazy things we see.’
It is unclear if obelisks are harmful or beneficial, but the team suggested they could ‘exist as stealthy evolutionary passengers.’
Scientists also said that these tiny, primitive entities may have played a critical role in shaping the biodiversity that exists on Earth today, as they could be capable of infecting organisms of many different species throughout their evolution.
Scientists aren’t yet sure whether these newly discovered lifeforms can make people sick, but there is one species of viroid that can: Hepatitis D.
Obelisks, viroids and viruses are all technically non-living organisms that depend on a host for survival. They don’t eat, regenerate or copulate.
Even so, some researchers believe that viroids and their relatives — perhaps obelisks too — represent Earth’s oldest ‘lifeforms.’
The research team, led by Stanford biochemist Ivan Zheludev, detected the obelisks by sifting through data from an RNA database containing thousands of sequences collected from human mouths, guts and other sources.
They analyzed this data to look for single-stranded circular RNA molecules that did not match any known viroid sequences and did not code for proteins.
Their analysis revealed 30,000 distinct obelisk types. Their genomes had previously been overlooked because they are so unlike any lifeform found and documented before.
But the findings, published in the journal Cell, indicate obelisks are anything but rare.
Researchers found half of the world’s populations is carrying obelisks in their mouth, while a small seven percent in their gut.
Further research will be needed to fully understand just how prevalent they are.
The type of obelisk varied based on what part of the body they were found in and which human sample they came from.
Long-term analysis suggested that a single obelisk type can live inside a human host for about a year.
The researchers believe these beings colonize bacterial cells in order to replicate, similarly to the way a virus infects a host and then replicates inside it.
They found evidence of this host-pathogen relationship in Streptococcus sanguinis, which is a common bacterial component of dental plaque. This microbe hosts a specific type of obelisk.
This is an important because this species of bacteria can be grown easily in the lab, allowing future studies to understanding how obelisks survive and replicate inside microbial cells.
All of the obelisks that have been discovered so far encode a major protein known as obulin, and many also encode a second, smaller form of this protein.
Obulins are completely unlike all other known proteins, and scientists still are not sure what purpose they serve or how they function.
At this time, scientists can only speculate about the evolutionary and ecological roles Obelisks play.
It’s possible that they could be parasitic and harmful to their host cells, but they could also be beneficial or totally benign.
If future studies reveal that obelisks have a significant impact on the health or functionality of the human microbiome, that would be an important discovery for human health, experts say.
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