Monster virus revived from melting permafrost

AS IF there weren’t enough problems with thawing tundra. A virus of unprecedented size  has been reactivated after being isolated from Russian permafrost 30,000 years old. Dubbed a pithovirus after the Greek pithos, meaning a large jar, the virus infects amoebas but does not appear to harm human or mouse cells. Even so, now that this virus has been revived from the permafrost, so too could potentially harmful microbes. “There’s good reason to think there could be pathogenic viruses in there too,” says Chantal Abergel of Aix-Marseille University in France. “This will certainly add a whole further and new dimension to  the thawing problem,” says Torben Christensen of Lund University in Sweden, who was not involved in the discovery. “It may mean that we are confronted not just with indirect climate warming impacts from thawing permafrost, but also direct, human-health-related issues.” Abergel and colleague JeanMichel Claverie revived the pithovirus by “baiting” their  peat-like permafrost sample with amoebas. “We used the amoebas to draw out the virus, as we know these giant viruses tend to infect amoebas,” says Claverie. The pithovirus really is a monster. At 1.5 micrometres long by 0.5 micrometres wide, it is around 30 per cent bigger than what had been the largest known virus – the pandoravirus, also found by Claverie’s team. The researchers were able to film the pithovirus’s entire life cycle. Once inside an amoeba, it migrates to the wall of a chamber called a vacuole. It does this with the help of an odd structure which serves as a kind of cork. Inside the vacuole, the cork is removed to initiate the infection, allowing   JULIA BARTOLI, CHANTAL ABERGEL/IGS, CNRS-AMU–Teeny whopperthe virus’s internal membrane  to fuse with that of the vacuole (PNAS, doi.org/rq7). The team is now hunting for other viruses in the permafrost sample, taken from the Kolyma region of northern Siberia. Claverie received it from a team led by Elizaveta Rivkina at Russia’s Institute of Physicochemical  and Biological Problems of Soil Sciences in Pushchino.  A year  ago, Rivkina and her colleagues revived a plant from the same layer of permafrost that eventually yielded the pithovirus. Claverie says that his team will look to revive viruses in much older permafrost samples, from as early as 3 million years ago. With untapped oil reserves hidden beneath the permafrost, Claverie warns of a health risk  to future prospectors. “If people become sick with strange symptoms, it might be wise  to quarantine and clear them  of dangerous new infections,”  he says. But Janet Jansson of the Lawrence Berkeley Laboratory in California says that most of the microbes found in permafrost  so far have been similar to  known ones. “I don’t think that permafrost per se should host more pathogens than any other environment.”