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Related Experiment Video

Updated: Jul 4, 2025

Human Colonoid Monolayers to Study Interactions Between Pathogens, Commensals, and Host Intestinal Epithelium

Human Colonoid Monolayers to Study Interactions Between Pathogens, Commensals, and Host Intestinal Epithelium

Published on: April 9, 2019

Viroid-like colonists of human microbiomes.

Ivan N Zheludev¹, Robert C Edgar², Maria Jose Lopez-Galiano³

¹Stanford University, Department of Biochemistry, Stanford, CA, USA.

Biorxiv : the Preprint Server for Biology

|January 31, 2024

Summary

Scientists discovered "Obelisks," a new class of RNA elements in the human microbiome. These viroid-like entities possess unique genetic features and are widespread globally, potentially impacting microbial communities.

Keywords:

Hepatitis Delta Virus Human Microbiome RNA metaviromics Viroid

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Area of Science:

Microbiology
Virology
Genomics

Background:

Viroid-like elements, termed "Obelisks," were identified in human gut metatranscriptomic data.
Obelisks exhibit distinct characteristics including circular RNA genomes, predicted secondary structures, and novel protein-coding regions.

Approach:

Analysis of human gut metatranscriptomic data revealed a novel class of RNA elements.
Phylogenetic analysis confirmed Obelisks form a distinct group unrelated to known biological agents.
Large-scale genomic searches identified numerous Obelisk instances across diverse environments and continents.

Key Points:

Obelisks are prevalent in human gut and oral microbiomes, with varying compositions across anatomical sites.
Some Obelisks encode hammerhead ribozymes, suggesting potential catalytic activity.
Obelisks were found within the bacterial species *Streptococcus sanguinis*, indicating potential host interactions.

Conclusions:

Obelisks represent a previously unrecognized, diverse class of RNA elements colonizing global microbiomes.
Their widespread presence and unique features suggest a significant, yet understudied, role in microbial ecosystems.