Video: Watch footage from the research team’s expedition to get samples from the vents.

Deep-sea hydrothermal vents look like alien worlds, their landscapes and fauna unlike any on Earth. Now a new study suggests that life works differently there too.

While studying the viruses that inhabit the scalding waters surrounding a vent in the Western Pacific, Eric Wommack noticed that a large proportion turned out to be docile tenants that lurk inside their bacterial hosts without causing much trouble. Marine phages – the viruses that parasitise bacteria and archaea in the sea – tend to infect their hosts, divide and burst them like balloons.

“We’ve never see that before anywhere else we’ve looked in the ocean,” says Wommack, a microbiologist at the University of Delaware in Newark, who built a device that sinks to the ocean floor and, with the help of a remote submarine, ferries 120-litre samples of water to a waiting boat.


Instead of hijacking bacteria to spawn offspring, these cell-splitting – or lysogenic – viruses insert their short genomes into the bacteria’s own, endowing it with potentially useful genes.

Survival genes

“Maybe the viruses that these bacteria are harbouring have genes that are aiding the bacteria in surviving in this harsh environment,” Wommack says.

During times of stress, the phages awake and churn out copies of themselves. During this awakening, viruses can mistakenly encapsulate bacterial genes and pass them onto new microbes.

For now, it’s unclear what sorts of genes the hydrothermal vent viruses shuttle between hosts. Of the 258 viral sequences Wommack’s team recovered from a thermal vent 2,500 m below the ocean surface, about 800 km west of Costa Rica, only a quarter matched known gene sequences.

Hydrothermal vent viruses could offer bacteria genes that help them cope with high heat, which deforms proteins, Wommack explains. Viruses could also help cells make a living by metabolising alternative sources of energy, such as sulphur, by shunting key metabolism genes from place to place.

To get a better handle on the lives of the viruses, Wommack plans to collect additional samples for further DNA sequencing. His team will also sample viruses from another vent off the coast of Baja, Mexico to see if the docile life is common to other locations.

Curtis Suttle, an expert on marine viruses at the University of British Columbia in Vancouver, agrees that lysogenic marine viruses could transfer novel features to bacteria. The bacteria that cause cholera, he notes, only causes disease when infected with a virus.

“There’s roughly Avogadro’s number (approx. 6 X 1023) of infections going on in the ocean, and every one of those interactions can result in the transfer of genetic information between virus and host,” he says.

Journal reference: The ISME Journal (DOI: 10.1038/ismej.2008.73)

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