Obelisks are considered one of the discoveries of 2024 in biology! These are RNA fragments recently detected in the oral and intestinal microbiota. It remains to be determined whether their long-term effects are positive, negative or neutral for the individual who hosts them.
The human gut microbiome regulates key functions such as digestion, metabolism and immune response, while playing a crucial role in protection against pathogens and in the production of vitamins and other beneficial compounds.
Read more: Can microbes be useful?
In this microscopic ecosystem, an imbalance (such as dysbiosis) can contribute to the development of inflammatory, metabolic and autoimmune diseases, and affect mental well-being.
Scientists studying the microbiome have identified new genetic components that had previously been little explored. This allows them to better understand how bacteria, viruses and things called plasmids (small fragments of DNA that bacteria sometimes share with each other) interact.
Genetic material with no clear function
Recently, attention has also focused on so-called viroids, small pieces of genetic material (circular RNA) that lack a protein coat and the ability to code for proteins. Research based on circular genome mapping also detected viroid-like RNA fragments.
Among the latter, the “obelisks” stand out. In fact, their detection in bacteria of the mouth and intestine can be considered one of the discoveries of the year.
This discovery was made by the research group of Ivan N. Zheludev from the Department of Biochemistry at Stanford in the United States, after applying a bioinformatics program called Viroid Nominator (VName) to the data of the Integrative Human Microbiome Project (iHMP). This new class of RNA agents forms a distinct and novel phylogenetic group. Additionally, they are present in various microbial ecosystems, such as the human gut.
Obelisks owe their name to their secondary structure composed mainly of rod-shaped or obelisk-shaped regions. These are circular RNAs which encode a new superfamily of proteins, the oblinswhose function is unknown.
The scientific community is making important steps toward understanding obelisks. Thus, the research team of Frederico Schmitt Kremer, from the Federal University of Pelotas in Brazil, has developed a new bioinformatics tool – Tormentor – to detect them even more effectively than through VNom.
Another research group from Duke University (USA) revealed that they are widely present in all RNA molecules of Streptococcus blood SK36 – a common dental plaque bacteria – although they are not present in its genome. This discovery is curious because it means that obelisks need a host cell to replicate, in this case the species Streptococcus that we have just mentioned.
If we add to this the fact that these biological entities can persist in individuals for more than 300 days, we can think that they have long-term effects on their hosts, but we still do not know if their presence is positive, neutral or negative. This opens a new field of study and even raises the possibility of redefining concepts that may have become obsolete, such as that of the microbiome.
Microbiome or microgenobiome?
The human body is estimated to host approximately 40 trillion bacteria, distributed among the digestive, respiratory, genitourinary, and other systems. Faced with this dizzying figure, and if we compare it to the approximately 30,000 billion cells that make up the body of an adult human being, the discovery of obelisks could prove to be momentous.
Read more: Is it true that there are more microbes than cells in the human body?
Until now, the concept of microbiome was limited to living microorganisms such as bacteria, viruses or fungi, but the emergence of obelisks makes this definition incomplete, since they are genetic components that do not have own cellular structure.
Before long, a consensus concept will likely emerge that takes into account not only obelisks, but also other genetic fragments called endogenous viral sequences. These are remnants of viruses that have been integrated into human DNA or are present in microorganisms in the body, but do not form complete, active viruses. This paradigm shift could mean that what we know today as the microbiome could be renamed the microgenobiome.
British writer Aldous Huxley wrote: “There is a world, but it is out there.” Perhaps it would be more appropriate to say, in light of recent discoveries, that “there is a world, but it is inside us.”
