New megavirus found

Researchers have managed to isolate what could be the largest virus ever discovered so far from ocean water off the coast of Chile. The virus, "Megavirus chilensis," is 10 to 20 times wider than an average virus, they said in the Proceedings of the National Academy of Sciences of the US. "Here, we present Megavirus chilensis, a giant virus isolated off the coast of Chile, but capable of replicating in fresh water acanthamoeba. Its 1,259,197-bp genome is the largest viral genome fully sequenced so far. It encodes 1,120 putative proteins, of which 258 (23%) have no Mimivirus homologs," they said. According to scientists Defne Arslan1, Matthieu Legendre, Virginie Seltzer, Chantal Abergel, and Jean-Michel Claverie, the new virus encodes 1,120 putative proteins, of which 258 (23%) have no Mimivirus homologs. In contrast, they said the DNA virus Mimivirus - previously considered the largest known virus in terms of particle size and gene content - has 979 proteins. But Claverie said the megavirus would not be hazardous to humans, according to a report on the BBC website. The BBC report said Mimivirus was found in a water cooling tower in the UK in 1992. The scientists believe Megavirus probably infects amoebas, single-celled organisms floating free in the sea. The BBC report said the new particle measures about 0.7 micrometers. "It is bigger than some bacteria," said Claverie, from Aix-Marseille University, Marseille, France. "You don't need an electron microscope to see it; you can see it with an ordinary light microscope," he added. Megavirus vs Mimivirus Like Mimivirus, Megavirus has hair-like structures, or fibrils, on the exterior of its shell, or capsid, that probably attract unsuspecting amoebas. A study of the giant virus's DNA shows it to have more than a thousand genes, the biochemical instructions it uses to build the systems it requires to replicate once inside its host. Lab experiments conducted by Claverie and colleagues where they infected fresh-water amoebas showed Megavirus constructed large trojan organelles, "cells within cells" that would produce new viruses to infect other amoebas. "Everything is initiated from a single particle, and then grows and grows to become this virion factory. That's why it needs all these genes," said Claverie. Ocean viruses BBC said there is an interest in ocean viruses because they have a major influence on populations of plankton, which form the base of many marine food chains. When viruses kill plankton, they help regulate the planet's geochemical cycles as the dead organisms sink into the deep, locking away their carbon for eons. — TJD, GMA News