News & AnalysisMicrobiology

Ever-Bigger Viruses Shake Tree of Life

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Science  19 Jul 2013:
Vol. 341, Issue 6143, pp. 226-227
DOI: 10.1126/science.341.6143.226

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A decade ago, the discovery in an amoeba of a virus that rivals the size of a small bacterium prompted a rethinking of how viruses originated and what they could do. Now, a team in France has described two new viruses with by far the largest genomes ever seen in a virus, including one that's bigger than the genomes of some parasitic eukaryotes. The two pandoraviruses, so named because of the viruses' amphora shape and the surprises they may portend, also have strikingly different genes and physical appearances from other viruses. Most of the pandoravirus genes don't look like any genes in known databases, suggesting the viruses originated from a totally different primitive cellular lineage than bacteria, archaea, and eukarya. The tree of life may need to be redrawn to account for these new viruses, some researchers say.