martes, 4 de marzo de 2014

Scientists revive a frozen 30,000-year-old giant Siberian virus

Climate change threatens to bring eradicated viruses back from the dead

Scientists revive a frozen 30,000-year-old giant Siberian virus

All it took was a single sample of frozen Siberian soil for an international collaboration of researchers to discover, and revive, a new type of "giant virus" — a virus whose unusually large size means scientists can spot it through a light microscope.

Indeed, despite being frozen for over 30,000 years, Pithovirus sibericum still packs a punch: a simple thawing procedure allowed it to infect a throng of unsuspecting single-cell organisms for the first time in thousands of years.

And given that climate change is already causing the ground to thaw in regions such as the Arctic and parts of Alaska , scientists fear that this lab experiment could eventually take to the field, leading to the spontaneous revival of ancient and unknown viruses.

The discovery puts the concept of "viral disease eradication" in a bit of a jam, says Jean-Michel Claverie, lead author of the study and evolutionary biologist at Aix-Marseille University, because it means that there could be a slew of "eradicated" viruses — viruses such as smallpox, which caused its last infection in 1977 , and the livestock disease rinderpest — laying dormant deep within the Earth's oldest frozen soil layers.

"We might be able to eradicate viruses from the surface of the planet," the researcher says, "but that doesn't mean that there isn't a single particle of that virus still alive somewhere."

Warm temperatures can prompt ancient frozen "giants" to infect anew

Claverie helped describe the first ever giant virus, dubbed Mimivirus, in 2003.

Prior to the finding, scientists and physicians mistook these massive viruses for bacteria or fungi.

The researchers also think that the Pithovirus is the oldest DNA virus revived to date.

To uncover the virus, Russian scientists first had to extract a sample of permafrost buried 30 meters below the surface in northeast Siberia.

"Just by retrieving the DNA, we can get a catalog of what is [in the permafrost] without reviving them."

Such a catalog should provide advanced warning of any possible pathogens lurking belowground.

"The regions of the Earth where viruses occur or that are affected by viruses, appear to extend to wherever life is found," says Curtis Suttle, a microbiologist at the University of British Columbia who did not participate in the study, "and permafrost is a rich source of microbial life."

viruses might also lay dormant in the ocean's deepest sediment

Moreover, Siberia's frozen soil probably isn't the Earth's only source of undiscovered viruses.

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