Scientists have discovered an unknown biological entity in the human microbiome that they have named “obelisk”. It’s not a virus, bacteria or anything like that.
The research behind this surprising discovery is the work of an international team led by Nobel Prize winner Andrew Fire and in which the Institute of Molecular and Cellular Biology of Plants (IBMCP), a joint center of the Polytechnic University of Valencia (UPV) collaborated. , participate. ) and the Superior Council of Scientific Research (CSIC), in Spain.
The microbiome is a complex microbiological ecosystem that resides in our body. It is home to an astonishing diversity of microorganisms that includes everything from viruses and bacteria to fungi and protozoa. We know more and more about this intricate biological network and its crucial role in health, intervening in functions as diverse as digestion, the immune system or even our own behavior.
Now, in the aforementioned study, signed, among others, by Ivan Zheludev and Andrew Fire, both from Stanford University in the United States, as well as by Marcos de la Peña, from the IBCP, a further level of complexity was discovered in our world revealed the microscopic interior: obelisks, minimal biological entities never seen before and that challenge our understanding of the limits of life.
Obelisks are new infectious agents with a tiny circular RNA genome of a few thousand nucleotides, far short of the RNA genomes some viruses use to reproduce. “These RNA circles are highly self-complementary, which allows them to adopt a stable rod-shaped structure reminiscent of the Egyptian monuments from which they are named,” explains Marcos de la Peña. “They lack the protein coat that characterizes viruses, but, like viruses, they are able to encode proteins,” underlines the CSIC researcher.
As a scientist working in 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 usual presence of self-cleaving 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 calls into question their origin and classification”, explains the researcher.
The discovery of the obelisks was possible thanks to bioinformatics studies on genetic sequences obtained from human feces; the presence of these RNAs was detected in 7% of the 440 subjects analyzed. Massive bioinformatic analyzes have also allowed the discovery of almost 30,000 species of obelisks in biological samples collected across the planet, both in natural ecosystems (soils, rivers, oceans…) and in wastewater or animal microbiomes. Among all this data, it was found that a strain of Streptococcus sanguinis, a common commensal bacterium in the microbiota of our mouth, accumulates obelisks very abundantly, finding that approximately half of the analyzed population contained obelisks in the oral cavity.
Recreation of intestinal bacteria (orange cells) infected with obelisks (black rods). (Image: IBMCP/CSIC/UPV)
The function and effects of the obelisks and the proteins they encode are still a mystery, as the researchers point out. The high accumulation of RNA genomes within bacteria would indicate, according to scientists, a possible role in the regulation of cellular activity with significant implications for health, since the microbiomes in which these bacteria live influence numerous physiological aspects, 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 demonstrates that the microbial world is much more complex than we imagined. “We have opened the door to an entirely new field of exploration that can revolutionize our understanding of virology, biology and even the very origin of life on Earth.”
The study is titled “Viroid-like colonists of human microbiomes.” And it was published in the academic journal Cell. (Source: Isidoro García / CSIC)
Interview Between Time.news Editor and Microbiome Expert Marcos de la Peña
Editor: Welcome, Marcos de la Peña! Thank you for joining us today to discuss this groundbreaking discovery of a new biological entity within the human microbiome known as “obelisk.” Can you start by giving us a quick overview of what obelisks are and why they’re so significant?
Marcos de la Peña: Absolutely! Obelisks are fascinating new entities that we’ve identified in the human microbiome. They are infectious agents characterized by a tiny circular RNA genome, which is unique in that it’s much smaller than the RNA genomes typically found in viruses. What sets them apart from viruses and even from plant viroids is that they do not have a protein coat, yet they retain the ability to encode proteins.
Editor: That certainly raises a lot of questions about their classification and origin. What are the implications of discovering something that sits between viruses and viroids?
Marcos de la Peña: Yes, it really challenges our established understanding of biological classification. Viroids, for instance, are notable because they are much smaller and don’t encode proteins, while obelisks have shown that life can exist in forms we hadn’t previously understood. This discovery suggests that there are additional layers of complexity within our ecosystems, particularly with respect to the microbiome. The implications for health and disease could be profound.
Editor: It’s intriguing to think about how much there is still to learn about our microbiome. Can you explain how the research team, led by Andrew Fire and including collaborators from various institutions, was able to identify these obelisks?
Marcos de la Peña: The discovery relied heavily on bioinformatics studies of genetic sequences derived from human fecal samples. We analyzed data from 440 subjects and found obelisks present in around 7% of those samples. Through a combination of this data and further massive bioinformatics analysis, we were able to identify nearly 30,000 species of obelisks from samples taken across the globe, including in natural ecosystems as well as human and animal microbiomes.
Editor: That’s quite a degree of diversity! How do you envision this finding affecting future microbiome research or potential medical applications?
Marcos de la Peña: This is just the tip of the iceberg! Understanding the role of obelisks could lead to new insights into their ecological functions and potential roles in human health. For example, if they influence disease processes or immune responses, there may be possibilities for therapeutic applications, similar to how we study more recognized microbes. It’s a call to expand our research into these lesser-known biological agents.
Editor: Considering how many different environments have yielded these obelisks, do you think they have the potential to adapt or evolve in unexpected ways?
Marcos de la Peña: Absolutely, their unique structure and properties suggest they may display remarkable adaptability. We must be vigilant in studying their behavior in various environments, as this could reveal how they interact with other microbiota and influence their hosts, whether in humans, plants, or other animals.
Editor: It sounds like we’ve barely scratched the surface of understanding the microbiome’s complexity. As someone deeply involved in this research, what excites you most about the future possibilities?
Marcos de la Peña: The potential for discovery is exhilarating! We are on the verge of unearthing entirely new realms of biology that could have lasting impacts on medicine, ecology, and our understanding of life itself. Each new finding, like the obelisks, brings us a step closer to unraveling these intricate networks.
Editor: Thank you for sharing your insights today, Marcos. Your work is crucial in expanding our understanding of the microbiome, and we look forward to seeing what else we’ll uncover in this fascinating field!
Marcos de la Peña: Thank you for having me! It’s been a pleasure discussing this exciting research with you.
