Viruses buoy life at hydrothermal vents

In the deep, dark ocean, viruses have won safe harbor through thievery.

With stolen genes that make sulfur-digesting enzymes, viruses provide metabolic backup to bacteria feasting on the sulfur plumes of hydrothermal vents, researchers propose May 1 in Science. In return, the viruses secure a host in the harsh depths of the sea.

Though the oceans are rife with bacteria-infecting viruses, called bacteriophage, researchers know little about the ones that invade sulfur-oxidizing bacteria. These bacteria are key sources of energy for organisms that live in hydrothermal vents. But the bacteria are difficult to study because they don’t grow in labs.

Geomicrobiologist Gregory Dick of the University of Michigan in Ann Arbor and colleagues spotted the genetic looters in samples from vents in the western Pacific Ocean and the Gulf of California. By sequencing DNA in each sample, the team found the genomes of sulfur-oxidizing bacteria and 18 types of viruses.

Fifteen of these viruses, the researchers found, had snatched and held onto bacterial genes involved in converting elemental sulfur to sulfite, a necessary step in energy production. By toting these filched metabolism genes, the authors suggest, the viruses bolster the host bacteria’s energy output.