New giant viruses found at an Austrian wastewater treatment plant probably evolved from a smaller virus that picked up bits of genome from its hosts and incorporated it, Frankenstein-like, into its own genetic code.
The viruses — four species in a new group dubbed the Klosneuviruses — are a type of Mimivirus. The giant viruses in the Mimivirus group were discovered just in 2003. Giant viruses live up to their name: They can reach sizes of up to 500 nanometers in diameter, compared to a few dozen nanometers for typical viruses. Giant viruses also have more complicated genetic machinery than their tinier cousins.
One of the new Klosneuviruses, for example, is so big that it carries transfer ribonucleic acids (tRNA) that can translate the genetic code for 19 out of the 20 protein-building amino acids found in nature. (Translation is part of the process in which a gene’s instructions are decoded and carried out. Viruses use tRNA in their replication process, but not all of them have their own tRNA; some hijack their hosts’.) That’s impressive, even for a giant virus, scientists led by Tanja Woyke of the Department of Energy’s Joint Genome Institute reported April 6 in the journal Science. [The 9 Deadliest Viruses on Earth]
“Since protein synthesis is one of the most prominent hallmarks of cellular life, it shows that these new viruses are more ‘cell-like’ than any virus anyone has ever seen before,” study co-author Eugene Koonin, a computational biologist at the National Institutes of Health, said in a statement.