Giant viruses are characterized by disproportionately large genomes and virions that house the viruses' genetic material. Scientists have been fascinated by giant viruses since 2003, when a group of French biologists led by Didier Raoult discovered the Mimiviruses. Another—a scenario championed by Koonin—presents the idea that giant viruses arose from smaller viruses. And Koonin believes there are more giant viruses waiting to be discovered in metagenomic data. One posits that giant viruses evolved from an ancient cell, perhaps one from an extinct fourth domain of cellular life.
New giant viruses suggest their genomes expanded like an accordion
Combined, the new viruses add2,500 additional gene families to the ones previously found in giant viruses. The giant viruses make a correspondingly giant coat, one that may have a lot more flexibility in terms of how much material it can hold. Only three of those appear to date back to the ancestor of all giant viruses. And a careful analysis of their genes suggests they, and all other giant viruses, have been put together through relatively recent evolution. This search put together three additional giant virus genomes, belonging to Catovirus, Hokovirus, and Indivirus.collected by :Sandra Alex
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