- Context (TH): Researchers recently discovered obelisks, which are biological entities within the human mouth and gut.
- Next-generation sequencing (NGS) was employed to analyze existing datasets from human microbiomes, facilitating the discovery of obelisks.
- NGS technology determines nucleotide sequences in genomes or specific DNA/RNA regions, enabling efficient, simultaneous sequencing of multiple fragments from diverse organisms.
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What are Obelisks?
- Obelisks are circular bits of genetic material containing one or two genes, self-organizing into a rod-like shape.
- The Obelisks’ genetic sequences are only around 1,000 characters (nucleotides) in size.
- They are made of RNA and proteins which facilitates self-replication within bacterial cells. Obelisks rely on microbial host cells, possibly bacteria or fungi, for replication.
- Obelisk genes perform identical functions across diverse bacterial strains.
- They are capable of vertically propagating from parent to offspring cells along with the host bacteria.
- Integrate loosely into the bacterial genome without disrupting standard cellular mechanisms.
- Obelisks fall between viruses and viroids in terms of classification.
- Similar to viroids, obelisks are circular single-stranded RNA genomes without a protein coat.
- Like viruses, obelisks contain genes predicted to code for proteins.
What is the difference between viruses and viroids?
| Features |
Viruses |
Viroids |
| Structure |
Nucleic acid core (DNA or RNA) surrounded by a protein coat (capsid) |
Short, circular RNA molecule (250-400 nucleotides) |
| Living or Non-Living? |
Non-living;
lack cellular structures and independent metabolic processes |
Non-living;
lack protein coats and protein-encoding capability |
| Replication |
Require host cells for replication, hijack host machinery |
Replicate within host cells using cellular enzymes |
| Genetic Material |
DNA or RNA |
RNA |
| Protein Synthesis |
Do not synthesize proteins independently; rely on host cells |
Do not encode proteins |
| Pathogenicity |
Infect animals, plants, and other organisms |
Infect plants and cause plant diseases |
| Examples |
Influenza virus, HIV, SARS-CoV-2 |
Potato spindle tuber viroid, Coconut cadang-cadang viroid |
To know more about Viruses and Viroids, refer to PMF IAS CA June 5, 2021.
