A virus found in the sea off Chile is the biggest in the world, harbouring more than 1,000 genes, surprised scientists reported on Monday.
The genome of Megavirus chilensis is 6.5 percent bigger than the DNA code of the previous virus record-holder, Mimivirus, isolated in 2003.
Viruses differ from bacteria in that they are usually far smaller and cannot reproduce on their own, needing to penetrate a host cell in which to replicate.
But M. chilensis is such a giant that it surpasses many bacteria in size and is genetically the most complex DNA virus ever described.
It was taken from sea water sample closed to the shore of Las Cruces, Chile. Its host organism is unknown.
DNA viruses include pox viruses and herpes viruses, but M. chilensis "doesn't seem to be harmful for humans," said Jean-Michel Claverie, of France's National Centre for Scientific Research (CNRS).
The study appears in a US journal, Proceedings of the National Academy of Sciences (PNAS).
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"A distant Mimivirus relative with a larger genome highlights the fundamental features of Megaviridae," by Defne Arslan, Matthieu Legendre, Virginie Seltzer, Chantal Abergel, and Jean-Michel Claverie, PNAS.