Out of Siberian Ice, a Virus Revived

Siberia fills the heads of scientists with dreams of resurrection. For millions of years, its tundra has gradually turned to permafrost, entombing animals and other organisms in ice. Some of their remains are exquisitely well preserved — so well, in fact, that some scientists have nibbled on the meat of woolly mammoths.

Some researchers even hope to find viable mammoth cells that they can use to clone the animals back from extinction. And in 2012, Russian scientists reported coaxing a seed buried in the permafrost for 32,000 years to sprout into a flower.

Now a team of French and Russian researchers has performed a resurrection of a more sinister nature. From Siberian permafrost more than 30,000 years old, they have revived a virus that’s new to science.

“To pull out a virus that’s 30,000 years old and actually grow it, that’s pretty impressive,” said Scott O. Rogers of Bowling Green State University who was not involved in the research. “This goes well beyond what anyone else has done.”

The thawed virus, which infects amoebae, is not a threat to humans. But if the new study holds up to scrutiny, it raises the possibility that disease-causing viruses may also be lurking in the permafrost.

The new virus was discovered by a group of researchers led by Chantal Abergel and Jean-Michel Claverie, a wife-and-husband team at Aix-Marseille University in France. Dr. Abergel and Dr. Claverie are veteran virus hunters, specializing in finding new species of so-called giant viruses.

Familiar viruses are tiny and have few genes. The influenza virus, for example, has 13 genes and is about 100 nanometers across. But giant viruses, which typically infect amoebae, can be 1,000 times bigger and have more than 2,500 genes.

Researchers at the Russian Academy of Sciences sent Dr. Abergel and Dr. Claverie small pieces of permafrost extracted from a Siberian riverbank in 2000.

To search for giant viruses in the samples, the French researchers added bits of the permafrost to colonies of amoebae to see if any viruses in the permafrost could infect them. The amoebae began to die — a sign that something in the permafrost was killing them. When the scientists examined the colonies, they discovered that giant viruses were multiplying inside the amoebae.

Measuring 1.5 micrometers long, the viruses are 25 percent bigger than any virus previously found. Their oddly long, narrow shape inspired the scientists to call them pithoviruses — “pithos” referring to ancient Greek earthenware jars.

“Sixty percent of its gene content doesn’t resemble anything on earth,” Dr. Abergel said. She and her colleagues suspect that pithoviruses may be parasitic survivors of life forms that were very common early in the history of life.

The scientists describe the pithoviruses this week in the Proceedings of the National Academy of Sciences.

“Its potential implications for evolutionary theory and health are quite astonishing,” said Eske Willerslev, an evolutionary biologist at the University of Copenhagen. Nonetheless, he said he didn’t think the scientists had fully ruled out the possibility that their samples had been contaminated with young viruses. “Without it, such claims remain nothing but biological curiosities,” Dr. Willerslev said.

Dr. Abergel and Dr. Claverie acknowledged the possibility of contamination. But they noted that they had performed the experiment three times and obtained the same virus from the permafrost each time.

It’s even possible that some of those viruses could infect humans instead of amoebae. Dr. Abergel and Dr. Claverie consider it a worrying possibility.

Dr. Rogers considered the risk of an outbreak of resurrected viruses to be “extremely low,” pointing out that scientists have been excavating permafrost and ice for decades without any known infections.

“But there’s always the first instance, right?” he added.