Scientists have explored multiple gigabytes of microbial DNA sequences to reveal their secrets. Photo Credit: Fabian Oswald
Within the DNA of unicellular lifeforms, a multitude of mysterious viruses lie dormant.
Using the high-performance computing cluster known as “Leo,” a research team from the University of Innsbruck has discovered over 30,000 previously unidentified viruses. These viruses, fascinatingly, were embedded in the DNA of unicellular organisms, with as much as 10% of microbial DNA composed of integrated viruses.
Image of Christopher Bellas. Credit: Christopher Bellas
The significant discovery was made by Dr. Christopher Bellas, Marie-Sophie Plakolb, and Prof. Ruben Sommaruga from the Department of Ecology. They had been conducting an in-depth study of unicellular microbes and unexpectedly found these concealed viruses encoded directly into the microbes’ genetic blueprint. This latent viral DNA may have the potential to generate fully operational viruses within the host cell.
Bellas expressed surprise at the abundance of viruses revealed through their research, with some microbes having up to 10% of their DNA made up of these hidden viruses. Intriguingly, these viruses don’t seem to harm their hosts. Some might even serve a protective role, resembling virophages which infect and eliminate other detrimental viruses within the host cell.
The Austrian Science Fund (FWF) sponsored the study, which was published in the esteemed journal Proceedings of the National Academy of Sciences (PNAS). Collaborations were made with scholars from the Max Planck Institute for Medical Research and the University of Groningen.
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Viruses: Protectors of Life?
Viruses infect all life forms, from bacteria to humans, persistently. While some are routinely present and occasionally cause symptoms, like the herpes virus in humans, others embed themselves within the host’s DNA. This study disclosed that many of the planet’s abundant unicellular eukaryotic (complex) organisms carry numerous viruses. These organisms can be found in diverse habitats, including algae in bodies of water, amoebae in soil, and even within human parasites.
Bellas shared that the reason for such a high prevalence of viruses in microbial genomes remains unclear. The leading theory is that these viruses safeguard the cell from infection by harmful viruses. Many unicellular eukaryotes are susceptible to infection by “giant viruses,” which are as big as bacteria and can destroy their host while replicating. However, the presence of a virophage can reprogram the giant virus to produce virophages instead, thereby potentially defending the host cell and saving its population.
Image of Ruben Sommaruga. Credit: Laura Sommaruga
The DNA of the newly found viruses is akin to virophage DNA, suggesting that the host microbes use these integrated viruses to defend themselves against giant viruses.
A Study Birthed from an Alpine Lake
Bellas and Sommaruga initiated the research project after discovering a new group of viruses in Gossenköllesee, an alpine lake in Tyrol, Austria, in 2021. They had aimed to trace the origin of these new ‘Polinton-like viruses’ but were unsure which organisms these viruses typically infected. To solve this, they conducted a broad-scale study encompassing all known microbial DNA sequences.
The vast dataset examined by the researchers consisted solely of DNA sequences, encoded by combinations of the nucleotide bases ATGC, and spanned several hundred gigabytes. Thanks to advanced technology and the high-performance computing power of “Leo,” the researchers could quickly analyze the enormous dataset. Microbial DNA sequences were also read using the cutting-edge Oxford Nanopore technology, which reads DNA by passing it through microscopic pores and detecting changes in electrical current caused by each base.
Ultimately, the scientists uncovered more than they were originally searching for, unearthing a plethora of hidden viruses. This unexpected find promises to stimulate further research into the roles these viruses play.
Source: “Large-scale invasion of unicellular eukaryotic genomes by integrating DNA viruses” by Christopher Bellas et al., Published on 10 April 2023, in Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2300465120
The Austrian Science Fund provided funding for the study.
Frequently Asked Questions (FAQs) about Hidden Viruses in Microbial Genomes
What are the “hidden” viruses discussed in the text?
The “hidden” viruses referred to in the text are more than 30,000 previously unknown viruses discovered within the DNA of unicellular organisms. These viruses are considered “hidden” because they were encoded directly into the organism’s genome and were previously undetected.
Where was the research conducted?
The research was conducted at the University of Innsbruck, in collaboration with researchers from the Max Planck Institute for Medical Research and the University of Groningen.
What technology did the researchers use to discover these hidden viruses?
The researchers used the high-performance computing cluster known as “Leo” to analyze large amounts of microbial DNA sequences. The sequences were also read using cutting-edge Oxford Nanopore technology.
What could be the potential role of these hidden viruses?
These hidden viruses may serve a protective role for the host organism. Some of these viruses are similar to virophages, which are known to infect and destroy other harmful viruses that may infect their host cell.
What is the significance of these findings?
These findings provide a deeper understanding of the microbial world, revealing an unexpected level of viral integration into unicellular organisms. They may also contribute to further studies on the roles these hidden viruses play in microbial health and disease, and even in larger ecosystems.
Who funded the research?
The study was sponsored by the Austrian Science Fund (FWF).
More about Hidden Viruses in Microbial Genomes
- University of Innsbruck
- Max Planck Institute for Medical Research
- University of Groningen
- Austrian Science Fund (FWF)
- Proceedings of the National Academy of Sciences (PNAS)
- Oxford Nanopore Technology
- Virophages – National Center for Biotechnology Information
