Obelisks and Viroids

Researchers recently discovered microscopic viroids-like biological entities called obelisks, in large numbers inside the human mouth and gut.

What are Obelisks?

• These are microscopic entities characterized by circular bits of genetic material that contain one or two genes and self-organise into a rod-like shape.
• Obelisks are a newly named class of viroid they discovered in the human gut and mouth.
• The secondary structure of viroids is a 3D shape they assume by folding onto themselves, this is predicted to look like a thin rod.
• Such a gene activities are called metatranscriptomes.
• Researchers found that Obelisks were present in roughly 7% of the metatranscriptomes from human feces and 53% in the mouth.
• This was found in the host S. sanguinis bacteria, and some Obelisks contained instructions for enzymes needed for replication, making them more complex than viroids.
• It is not known if it could harm or affect human health, but may shape the human microbiome.

What are Viroids?

• Viroids are tiny loops of Ribonucleic acid (RNA) found to infect primarily plants, such as potatoes.
• They differ from RNA-based viruses, as they are naked and lack the protective shells that viruses use to hold their genetic material.
• Their RNA does not contain instructions to build proteins, whereas viruses carry instructions for their outer shells and for certain enzymes they need to replicate.
• Viroids designate these enzymes from their hosts.
• Based on recent studies, viroids were once thought to infect only plants, but may infect additional hosts like animals, fungi or bacteria.
• Researchers searched for possible viroids among the genes of microbes that reside in the human body.

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