Up until recently, the line between viruses and cells seemed pretty simple: cells were big and carried everything they needed to live and grow. Viruses were tiny and only carried the genes they needed to take over their host cells; they relied on their hosts for most essential proteins.
That line got a bit blurry as we found parasitic and symbiotic cells with very stripped-down, minimalist genomes that wouldn’t let them survive outside their hosts. But it’s nearly been obliterated by the discovery of giant viruses—some of these have genomes that are larger than those of bacteria and carry many of the genes needed to copy DNA and translate it into proteins.
Scientists have now identified yet another giant virus, this time using a technique that sounds like it’s straight out of a sci-fi horror flick: they thawed some 30,000-year-old permafrost and allowed any viruses present to infect some cells. Fortunately, the cells were amoebas, and this virus is overwhelmingly unlikely to present a threat to human health. But the fact that viruses could apparently survive so many centuries in the Siberian permafrost does lead the authors to suggest that the melting Arctic may pose an emerging disease risk.
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