Ocean archaea more vulnerable to deep-sea viruses than bacteria

Deep-sea viruses aren’t just dealers of disease; they’re crucial players in Earth’s nutrient cycles. In marine sediments, virus assassinations of single-celled life-forms called archaea play a much larger role in carbon and other chemical cycles than previously thought, new research suggests. For instance, those microbial murders release as much as 500 million metric tons of carbon annually worldwide, researchers report online October 12 in Science Advances.

Viruses are a major killer of bacteria and archaea in the deep sea, busting open infected cells like water balloons and spewing the cells’ innards. To find the relative number of massacred microbes, marine ecologist Roberto Danovaro of Polytechnic University of Marche in Ancona, Italy, and colleagues studied the spilled guts of the viruses’ victims.

Tallying the number of archaeal versus bacterial genes released from the carnage in more than 480 sediment samples, the researchers discovered that viruses kill archaea disproportionately more often than bacteria. Despite making up on average about 12 percent of the microbial population in the top 50 centimeters of sediment, archaea accounted for up to one-third of the total biomass killed by viruses, Danovaro and colleagues report. The researchers do not speculate on why archaea were such frequent targets. Those deaths were not in vain, though: Archaea corpses supply nutrients such as carbon that help sustain other life-forms.