An international team of scientists discovered a new biological entity in the microbiome of humanswhose unique characteristics place it between viruses and tiny viroids, without being either type of infectious agent.
From now on, The new element, called “obelisk”, will be studied and classified by biologists who will have to “explain what exactly this new step on the ladder of life is”Marcos de la Peña, researcher at the Institute of Molecular and Cellular Biology of Plants (IBMCP) and co-author of the study, explains to EFE.
“This finding not only changes our conception of the biological scale on the planet, but also shows that we probably still have a lot to discover in the microbiological world,” emphasizes the Spanish virologist.
The study, carried out using bioinformatics analysis, discovered that these new biological entities are part of our microbiome, a complex microbiological ecosystem formed mainly by bacteria, as well as fungi, protozoa, and their parasites, such as viruses.
This complex biological network plays an essential role in our health and is responsible for metabolic diseases, such as obesity and diabetes, or autoimmune disorders and mental illnesses, hence the importance of studying its components, functions and interactions.
The details of the discovery, led by the Nobel Prize winner Andrew Fire of Stanford Universitywere published in the journal Cell.
A chance find
On the biological scale, viroids are the smallest known infectious agents; They are below the viruses, “and we know that they infect plants but there are also some agents very similar to viroids, such as the virus of the hepatitis “Human D and other similar RNAs, which infect animals”comments De la Peña.
“But we had been suspecting for some time that there had to be something more, because it was surprising that these simple circular RNA infectious agents were in the minority (only about 50 species were known since their discovery 50 years ago) and only infected complex organisms such as animals and plants.” .
Furthermore, in recent years “We had found many indications that they could also be infecting simpler and more widespread organisms on the planet, such as bacteria”says the Spanish researcher.
With that idea, Ivan Zheludev, from Stanford University, “decided to analyze the human microbiome, analyzing stool samples from previous studies of patients with various intestinal problems.”
Through bioinformatic analysis, it was detected that around 7% of the samples contained novel minimal RNA subviral agents that were baptized as ‘obelisks’ and that they were present in sick and healthy people, that is, “they did not seem to be correlated with any disease”.
In subsequent studies, the researchers were also able to detect obelisks in the oral microbiota, in a strain isolated from the Streptococcus Sanguinis bacteriacommon in our mouth.
After bioinformatically analyzing millions of genetic data, they confirmed that these new infectious elements are distributed throughout the planet and Up to 30,000 new species of obelisks have been detected in environmental samples of all types (animal microbiomes, rivers, soils, seas, etc.).
Structure and function of obelisks
Obelisks, named for their elongated rod shape, are simple mobile genetic elements that infect bacteria, although researchers do not rule out that they can infect other more complex organisms “such as fungi or protists, among others,” says De la Peña.
“Now we have to see how they work at the molecular level and how they replicate. We know that the simplest RNA viruses need a genome size greater than 3,000 nucleotides but obelisks barely exceed 1,000far below that of viruses, but which, however, allows them to encode one or two proteins. Furthermore, their circular RNA genome and structure give them a series of new characteristics that make them different from everything we knew,” he details.
“In any case, we are talking about something that surrounds us, and that, although we have just discovered it, has probably been playing a role in nature for many millions of years that we will now have to reveal,” he comments, and that “We believe that this new door that opens could revolutionize our understanding of virology, biology and even the origin of life on Earth”maintains De la Peña.