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Researchers have resurrected a 700 year old virus they discovered in caribou poo.

The team say their would shows the potential for bringing back other viruses to study their biology and work out how to beat them.

The new viruses are hundreds of years old, and one of them probably infected plants the caribous ate.

700 year old frozen Caribou excrement: A careful examination turned up two never-before-seen viruses which researchers were able to resurrect

The findings prove viruses can survive for surprisingly long periods of time in a cold environment, according to Eric Delwart, a researcher at Blood Systems Research Institute in San Francisco.

His team analyzed the viral genetic material contained in a core drilled through layers of accumulated caribou feces up to 4,000 years old in an ice patch in Canada's Selwyn Mountains.

Caribou congregate on ice patches to escape insects and summer heat, and deposit feces containing partially digested plant material. 

The authors isolated the complete genome of a DNA virus from a 700-year-old ice core layer that was distantly related to plant and fungi-infecting viruses, and a partial viral RNA genome that was related to an insect-infecting cripavirus. 

The appearance of the viral material in the fecal samples suggests that the viruses may have originated in plants eaten by the caribou or flying insects attracted to the material. 

Using a reverse genetics approach, the authors reconstituted the genome of the DNA virus to confirm whether the virus might infect plants.

They then introduced it to Nicotiana benthamiana, a close relative of tobacco, where it successfully infected both new leaves and leaves inoculated with the virus 

Caribou congregate on ice patches to escape insects and summer heat, and deposit feces containing partially digested plant material.

Plants inoculated with the ancient viral DNA displayed evidence of infection including replication of viral DNA in inoculated and newly emerging leaves. 

According to the authors, cryogenically preserved environmental samples may preserve ancient viral genetic material for present day study.

'Our finding indicates that cryogenically preserved materials can be repositories of ancient viral nucleic acids, which in turn allow molecular genetics to regenerate viruses to study their biology,' the team wrote.

Using reverse genetics, the team reconstituted the DNA virus, which replicated and systemically spread in a model plant species.

'Knowledge of ancient viruses is limited due to their low concentration and poor preservation in ancient specimens. 

'Using a viral particle-associated nucleic acid enrichment approach, we genetically characterized one complete DNA and one partial RNA viral genome from a 700-y-old fecal sample preserved in ice. 

'Using reverse genetics, we reconstituted the DNA virus, which replicated and systemically spread in a model plant species. 

'Under constant freezing conditions, encapsidated viral nucleic acids may therefore be preserved for centuries. ' 

As Arctic ice melts faster with climate change, it could release ancient viral particles into the environment—some of which could remain infectious, the team warns.