TAG: GS 3: SCIENCE AND TECHNOLOGY
THE CONTEXT: Recently, scientists at Stanford University have introduced a novel life form, ‘obelisks,’ discovered during the analysis of genetic material from bacteria in the human gut.
EXPLANATION:
- The boundaries between the living and non-living realms have long been defined by viruses and viroids, challenging traditional notions of life.
- This discovery further blurs the lines between the living and non-living, adding a new layer of complexity to our understanding of life.
Viruses, Viroids and obelisks:
- Historical Context:
- Since 1898, viruses have been the primary entities bridging the gap between living and non-living, characterized by host dependence and small genome sizes.
- Viroids Emergence (1971):
- Viroids, discovered by Theodor Diener, showcased a simpler form of life with naked RNA, lacking protein coats and lipid layers. Viroids presented an intriguing departure from traditional definitions of life.
- Stanford’s Revelation:
- Using next-generation sequencing (NGS), researchers at Stanford identified a new life form, ‘obelisks,’ in the genetic material of bacteria from the human gut.
- NGS Technique:
- The power of NGS is likened to assembling scattered pages in a library, allowing the reconstruction of genome sequences from bits and pieces obtained from different organisms.
Obelisks:
- The Stanford team developed a software script to identify obelisks by looking for circular RNA genomes in bacterial RNA fragments.
- Analysis of 5.4 million publicly available datasets revealed approximately 30,000 distinct obelisks in the human gut.
- Further exploration found obelisks in oral bacteria on a global scale.
- RNA Length and Coding:
- Obelisk RNA, unlike viroids, is longer (around a thousand base pairs) and appears to code for two unique proteins, with no resemblance to known proteins from other life forms.
- Comparative Analysis:
- Despite circular RNA similarities with viroids, obelisks exhibit distinctive features, raising questions about their origin and function.
Challenges and Limitations:
- The study faces challenges in attributing specific obelisks to their bacterial hosts due to analyzing RNA data collectively.
- However, a link to Streptococcus sanguini was established through individual bacterial analysis.
- Key questions arise about obelisks’ reproduction, transmission, potential pathogenicity, evolutionary history, and their role in human health and disease.
- Proof of Concept: The connection of a specific obelisk to Streptococcus sanguini in laboratory-grown bacteria suggests a potential avenue for further exploration.
Viruses:
- Viruses are microscopic organisms that can infect hosts, like humans, plants or animals. They’re a small piece of genetic information (DNA or RNA) inside of a protective shell (capsid). Some viruses also have an envelope. Viruses can’t reproduce without a host. Some common diseases caused by viruses include the flu, the common cold and COVID-19.
Viroids:
- Viroids are non-coding circular RNA molecules with rod-like or branched structures.
- They are often ribozymes, characterized by catalytic RNA. They can perform many basic functions of life and may have played a role in evolution since the beginning of life on Earth.
- They can cleave, join, replicate, and undergo Darwinian evolution. Furthermore, ribozymes are the essential elements for protein synthesis of cellular organisms as parts of ribosomes.
- Thus, they must have preceded DNA and proteins during evolution.
Conclusion:
- The discovery of obelisks opens a new chapter in the exploration of life’s complexity, challenging preconceived notions and prompting further research. As scientists delve deeper into the mysteries of obelisks, a clearer understanding of their role in the intricate web of life may emerge, pushing the boundaries of our comprehension of living organisms. The distinction between the living and non-living at the far reaches of life continues to evolve, leaving the scientific community with a captivating and challenging frontier to explore.
SOURCE: https://www.thehindu.com/sci-tech/science/rna-obelisk-next-generation-sequencing/article67891037.ece
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