The finding has renewed the debate about the place of giant viruses on the evolutionary tree.
Austrian microbiologists have discovered a virus that stands out from congeners by the size and complexity of the device. “Record holder” found in the wastewater of the town of Klosterneuburg in the East of Austria, has a diameter of about 400 nanometers. In honor of the place of detection of a virus called Klosneuvirus.
The virus was discovered using the Arsenal of methods metagenomic. Simply put, the genome of the virus collected in parts of the fragments that were present in the sample. This approach allows researchers to study the set of genes of all microorganisms present in the sample environment without their cultivation in the laboratory. Themselves the authors appreciate the find as a fact, and reported the probable discovery of three related species in the nearby area.
The discovery rekindled debate about whether periodically opened in the last fifteen years, a giant virus with viruses in the strict sense of the word, or before us the former living cells, once become parasites and on the long evolutionary path to lose a fair amount of genetic information together with the fixtures, which encode “thrown”. In this case, it would seem logical definition as a separate domain, on an equal footing with bacteria, eukaryotes and archaea.
The size of some known viruses
The polio virus is~30 nm Virus – Zeke~45 nm
Adenovirus~90 nm HIV-1~120 nm
Indeed, most viruses are much smaller cells, in which is embedded, and has a very modest size of the genetic material. Some types of avian and swine viruses for reproduction cost only two genes against thousands of even ordinary bacteria. So, for example, all known E. coli contains genes 4400 — and that’s not a record. Known viruses-giants (the first opened in 2003, and all of them described about half a dozen) contain of the order of one to two thousand genes each, which clearly exceeds the number necessary for “capture” of the cell and its subsequent use. Some organisms are obviously capable of independent life and reproduction cost less.
Skeptics do not see in the fourth domain need explaining genetic redundancy in a virus-giants of borrowing material owners. So, Eugene koonin (national center for biotechnology information, Bethesda, MD) calls “crystal clear” that a virus-giants belong to groups, which includes far more small form. Overall, to this point of view tend and the authors themselves open. Together with colleagues, they showed that giant viruses are gradually borrowed genetic material from different hosts. “There is no evidence of the existence of a fourth domain, and this document proves it,” says Curtis Suttle, a virologist from the University of British Columbia (Vancouver, Canada).
In addition, skeptics have questioned the fact of the opening. Microbiologist Didier Raoult (Didier Raoult) from the University of Marseille, says that before drawing conclusions about evolution based on the genome, it would be nice to see its owner. The gene sequence itself is a minor argument: they often change places, and undergo other changes, masking their origin.
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