An international team led by Nobel Prize winner Andrew Fire and involving the Institute of Molecular and Cellular Plant Biology (IBMCP), a joint center of the Polytechnic University of Valencia (UPV) and the Higher Council for Scientific Research (CSIC) , a dependent organization of the Ministry of Science, Innovation and Universities (MICIU), has discovered a new biological entity in the bacteria that live in our mouth and intestines.
This organism, which they called Obelisk because of its shape, is a new infectious agent whose genome is simpler than that of viruses, and whose function and effects on our health are still unknown. This discovery, made through bioinformatics studies of genetic sequences obtained from human stools, opens new questions about the origin and evolution of microbiological diversity. The discovery is published today in the journal cell.
The microbiome is a complex microbiological ecosystem that resides throughout our body. It hosts an astonishing diversity of microorganisms, ranging from viruses and bacteria to fungi and protozoa. We know more and more about this complex biological network and its crucial role in health, involved in functions as varied as digestion, the immune system and even our own behavior.
Today, a multidisciplinary team led by Nobel Prize winner Andrew Fire from Stanford University (United States), in collaboration with the CSIC team of researchers Marcos de la Pena at the IBMCP in Valencia and the University of Toronto (Canada), revealed an additional layer of complexity in our inner microscopic world: obelisks, minimal biological entities never before seen and which challenge our understanding of the limits of life.
Discovery in the human microbiome
Obelisks are new infectious agents with a tiny circular RNA genome of just 1,000 nucleotides, well below the RNA genomes that some viruses use to reproduce. “These RNA circles are highly complementary, allowing them to adopt a stable rod-shaped structure reminiscent of the Egyptian monuments that give them their name,” explains Marcos de la Peña. “They do not have the protein envelope that characterizes viruses, but, like viruses, they are capable of coding for proteins,” underlines the CSIC researcher.
As a scientist working at a plant research center, de la Peña points out that obelisks are reminiscent of viroids, a family of subviral agents that infect plants and with which they share the circular RNA genome and the presence habitual self-excessive ribozymes. . “However, plant viroids are even smaller, around 300 or 400 nucleotides, and do not code for proteins. For all these reasons, Obelisks are halfway between viruses and viroids, which poses a challenge as to their origin and their classification,” specifies the researcher.
The discovery of the Obelisks was possible thanks to bioinformatics studies of genetic sequences obtained from human stools, the presence of these RNAs being detected in 7% of the 440 subjects analyzed. Massive bioinformatics analyzes have also enabled the discovery of nearly 30,000 species of Obelisks in biological samples collected all over the planet, both in natural ecosystems (soils, rivers, oceans, etc.) and in wastewater or animal microbiomes.
Among all this data, it was detected that a strain of Streptococcus Sanguinisa common commensal bacteria in the microbiota of our mouth, accumulates obelisks very abundantly, and approximately half of the analyzed population was found to contain obelisks in their oral cavity.
New frontier in biology
The function and effects of obelisks and the proteins they encode remain a mystery, the researchers point out. The high accumulation of RNA genomes inside bacteria would indicate, according to scientists, a possible role in the regulation of cellular activity with significant implications for health, since the microbiomes where these bacteria live influence many aspects physiological, from digestion to the immune system.
Furthermore, the discovery of the Obelisks raises fundamental questions about the origin and evolution of viruses and microbiological diversity. According to De la Peña, “this discovery shows that the microbial world is much more complex than previously imagined. “We have opened the door to a whole new area of exploration that can revolutionize our understanding of virology, biology and even the very origin of life on Earth. »
