American scientists have made the analysis of the diversity of viruses, browsing a public database metagenomes (isolated from the environment sets of genes). The article States that the researchers collected the hypothetical genomes of 501 for various types of large nuclear-cytoplasmic DNA-containing viruses that primarily live in aquatic environment, where they infect unicellular algae. It turned out that giant viruses have a huge variety of genes that participate in cellular metabolism, particularly in the absorption of nutrients and nitrogen metabolism.

In earlier studies of giant viruses discovered genes that, as is commonly believed, was obtained by horizontal gene transfer. This suggests that the viruses might get DNA from infected hosts. However, in this case, it was revealed evolutionary changes in genes, indicating close contacts between infectious agents and their hosts. According to scientists, the virus-specific metabolic genes could be purchased millions or billions of years ago.

From the point of view of researchers, as soon as such a virus infects a unicellular organism, it begins to restructure fundamental aspects of cell physiology. It redefines the traditional view of viruses, whose effects on human body was considered through the impact on mortality of infected organisms, not how they change their functions.