French researchers have discovered a new giant virus that surpasses all previously known giant viruses. However, the researchers are puzzled because the genes of the giant virus do not resemble any known life form. Nadège Philippe, a French researcher from Aix-Marseille University in Marseille, discovered two new giant viruses that raise more questions than they currently answer. One giant virus was found in a river mouth off the coast of Chile, and the other was found in the mud of a pond near the city of Melbourne. Although one giant virus was found in saltwater and the other in freshwater, both giant viruses are remarkably similar. The researchers named the previously unknown and extremely puzzling particles Pandoraviruses – named after Pandora’s box, which contains an eerie surprise.
Viruses are tiny particles that spread outside of cells through transmission. Unlike bacteria, which are much larger than viruses, they do not even consist of a cell, which is why they are not considered living organisms. The first giant virus was discovered by researchers about ten years ago in a cooling tower in Bradford, England. At that time, the researchers were looking for bacteria and initially believed they had found them. However, it later turned out that the 0.7-micrometer particles were not bacteria but viruses – the largest known at the time, which shifted the boundaries and classification criteria of viruses. This was not only due to the size of the viruses but also to the length of the genetic material, which comprised more than one million bases – more than some bacterial genomes.
In recent years, researchers have discovered more and more giant viruses. However, the two new Pandoraviruses overshadow everything that has been seen before: the length of the viruses is one micrometer, and a virus has twice as many base pairs as the previous record holder. The biggest mystery that scientists have not yet been able to solve is the DNA of the giant viruses. 93 percent of the genes of both Pandoraviruses are completely unknown to science. They cannot be traced back to any known cell lineage. Where the researchers should place the Pandoraviruses in the tree of life and how they originated is still completely unclear.
