An article published in the journal “Nature Communications” describes the discovery of two species of giant viruses that were called Tupanvirus, attributed to the Mimiviridae family, the same that includes other giant virus species discovered in recent years. A team of researchers from various international institutions discovered these two viruses that are larger than some bacteria and have some unusual characteristics for viruses, such as the genes for the synthesis of a lot of proteins.
Giant viruses were discovered in 2003 and the first ones were called Mimivirus. Over the next few years, other really huge viruses were discovered and the Mimiviridae family was created to include a number of those species. They include the Klosneuvirus group, whose discovery was announced in April 2017.
Now two giant viruses discovered in Brazil have been added to these giant viruses: these are the Tupanvirus, one called ‘soda lake’, since it was found in very alkaline lakes in the Brazilian wetland of Pantanal, and the other one ‘deep ocean’, because it was discovered at 3,000 meters of depth among ocean sediments off Rio de Janeiro.
These two new giant viruses have various peculiar characteristics such as genes to synthesize a considerable amount of proteins, 1276 for the soda lake species and 1425 for the deep ocean species. More importantly, Tupanviruses possess the genes to synthesize all 20 essential amino acids crucial as life’s building blocks.
One of the parameters used to distinguish viruses from autonomous cells is the biological process known as translation. In very simple words, viruses need a host to synthesize proteins so they’re not autonomous.
Tupanviruses have the largest translational apparatus ever seen among viruses but that’s not enough to make them autonomous. However, their characteristics put them on the boundaries between the world of viruses and that of cell organisms. They are also the boundaries between living and non-living organisms with discussions about the nature of viruses.
Mimiviruses infect amoebas to reproduce and from this point of view Tupanviruses seem more efficient because they can infect more types of amoebae. The analysis of these new giant viruses has just begun because about 30% of their genome is currently unknown. The continuous discovery of new giant viruses and the progress of genetic techniques will surely bring more surprises.