While analyzing the genomes of single-celled microbes, a group of researchers made a surprising discovery: thousands of unknown viruses are “hidden” in their DNA.
Researchers have found the DNA of more than 30,000 viruses integrated into the diverse genomes of single-celled microbes, they report in a new study. They explained that viral DNA can enable a host cell to replicate fully functional viruses.
“We were very surprised by the number of viruses we found in this analysis. In some cases, this has been up to 10% of viruses,” said lead author Christopher Pellas, an ecologist who works on viruses at the University of Innsbruck in Austria. Microbe DNA consists of hidden viruses.” .
These viruses don’t seem to infect their hosts and could be beneficial, the researchers say. Some of the new viruses resemble phages, a type of virus that infects other pathogenic viruses that try to infect host cells.
“It is not yet clear why microbes have so many viruses in their genomes. Our strongest hypothesis is that they protect the cell from infection by dangerous viruses,” said Bellas.
Living on Earth means dealing with viruses, the most abundant biological creatures on the planet, which together infect every form of life. They are very diverse and use many different tactics to exploit the cellular host.
Regardless of semantic debates about whether viruses are alive or not, they certainly insert themselves into the lives of other organisms. Some even replicate by inserting their DNA into a host cell and becoming part of its genome.
When this happens in a germ cell, it can give rise to internal viral elements (EVE) or viral DNA that is passed from one generation to the next in a host species.
Scientists have discovered the drug virus infects a wide variety of organisms, including animals, plants, and fungi. For example, mammals carry various viral fragments in their DNA, and about 8% of the human genome consists of DNA from ancient viral infections.
The authors of the study explained that many of these are no longer functional and are considered “genetic fossils.” Research suggests that endogenous viral components may be adaptive in humans and other organisms, although they may help ward off modern viruses.
The researchers note that this is true for many single-celled eukaryotes, noting that these microbes are often infected and killed by giant viruses.
And if phages already live in a host cell, they can save the host by reprogramming a giant virus to form phages instead of replicating themselves.
The DNA of the newly discovered viruses is similar to the DNA of phages, suggesting that microbes may offer some protection against giant viruses thanks to “integrated” viruses found in their genomes, according to in new research.
The researchers write that until now, the study of EVEs has focused primarily on animals and plants, with little interest in protists—that is, eukaryotic organisms that are not animals, plants, or fungi—although and they represent the majority of eukaryotic biodiversity on Earth. .
Planning to study a new group of viruses they found in the waters of Gusenkolssee, an alpine lake in the Austrian state of Tyrol, Bellas and his colleagues originally intended not to discover thousands of new viruses hidden in DNA of microbes.
“In our work, we first wanted to find the source of the ‘Bolinton-like virus’. But we usually don’t know which organisms these viruses can infect. So we did a massive study to test all the microbes. The DNA sequence is known,” said Bellas.
To do this, they enlisted the help of Leo, a high-performance computing group at the University of Innsbruck that can efficiently analyze large volumes of data.
Noticing genes from phages and other viruses in several microbial genomes, the researchers decided to conduct further research using Leo to systematically analyze all publicly available sets of protist draft genomes.
They discovered that autologous viral elements are “hidden in repetitive regions of single-celled eukaryotic genomes that are difficult to assemble,” and noted that thousands of assembled viruses in several species show that the viruses constitute a large unrecognized protogroup. – genomes.
The study also found evidence that many endogenous viral elements are not only genetic fossils but also functional viruses, the researchers wrote, suggesting that different sequences of these elements may be part of a host antiviral system.
The study was published in the Proceedings of the National Academy of Sciences.
Source: ScienceAlert
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