Geneticists from the University of Innsbruck have discovered more than 30,000 previously unknown viruses that were “hiding”
The discovery was made during anotherproject aimed at studying the origin of a new group of viruses that scientists have discovered in a lake in Austria. Since it was not known exactly which organisms infect these viruses, the scientists decided to conduct a large-scale screening of all microbes whose DNA code is known.
The researchers analyzed a huge setdata using a powerful university computer cluster. Although the data contained only DNA sequences, that is, the sequence of nucleotides (adenine, guanine, cytosine and thymine) that code for all genes, it is several hundred gigabytes.
As a result of the study, scientists found muchmore than the viruses they were looking for. The analysis showed that many of the numerous unicellular eukaryotic (complex) organisms of the Earth are filled with viruses. In total, scientists counted more than 30 thousand previously unknown viruses. These "infected" organisms are ubiquitous and include large numbers of algae in lakes and oceans, amoebas in the soil, and human parasites.
Why so many viruses are found in the genomes of microbes is not yet clear. Our strongest hypothesis is that they protect the cell from infection by dangerous viruses.
Christopher Bellas, study co-author
These viruses do not harm their hosts,scientists note. On the contrary, many of them appear to be similar to so-called virophages, which infect and destroy other harmful viruses. Many eukaryotic single-celled organisms are infected by “giant viruses,” a group of viruses that can be as large as bacteria. When the virophage is in the host cell, it "reprograms" the giant virus to create virophages.
As a result, the giant virus sometimes succeedsreflect, and the host cell population is saved from destruction. The DNA of newly discovered viruses is similar to that of virophages. Therefore, it is likely that host microbes protect themselves against giant viruses with these embedded viruses.
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On the cover: artistic illustration of the genetic year of unicellular organisms. Image: University of Innsbruck