In a groundbreaking discovery, a team of scientists from Stanford University has unveiled a new and intriguing class of virus-like entities termed “obelisks.” These entities have been identified within bacteria residing in the human mouth and gut, showcasing genomes composed of RNA loops. This discovery challenges conventional definitions of life and introduces a fascinating dimension to the understanding of microbial interactions.
Unlike traditional viruses, obelisks display unique characteristics. The Stanford team, led by biologist Andrew Fire and graduate student Ivan Zheludev, employed advanced software to analyze existing gene catalogs from microbes inhabiting the human body. Their search resulted in the prediction of nearly 30,000 RNA circles, each about 1000 bases long, suggesting the existence of distinct obelisks. Notably, these entities seem different from bona fide viruses, as typical RNA viruses possess a much larger number of bases. However, some obelisk sequences encode proteins involved in RNA replication, imparting a level of complexity beyond standard viroids.
Viroids, infectious loops of RNA without traditional protein shells, were initially discovered in plants. The recent identification of viroid-like circular RNA genomes in various life forms, including animals and bacteria, has expanded scientific interest in these entities. The Stanford researchers’ innovative approach to identifying obelisks involved predicting circular RNA structures similar to those found in viruses and viroids. This pioneering method revealed obelisk sequences in 7% of human gut bacteria and half of the bacteria in the human mouth, each displaying distinctive sequences depending on their microbial origin.
While the impact of obelisks on human health remains uncertain, their presence in diverse microbiomes suggests an unexplored class of RNAs that has colonized human and global microbial ecosystems. This finding underscores the complexity of the viral universe, prompting scientists to reconsider the evolution of viruses. One intriguing question emerging from this discovery is whether viruses evolved from increasingly complex structures like viroids and obelisks or if they emerged first and then degenerated into simpler forms.
The research, outlined in a preprint posted on bioRxiv, signifies a significant leap in understanding the intricate relationships between microbial entities and their hosts. As scientists delve into the frontiers of virology, the study of obelisks opens new avenues for exploring the long-term evolution of viruses on Earth. This groundbreaking work provides a glimpse into a microbial world filled with surprises, pushing the boundaries of our knowledge in the field of life sciences.
https://www.science.org/content/article/it-s-insane-new-viruslike-entities-found-human-gut-microbes