On the Earth’s surface, plants use photosynthesis to convert sunlight into food. In the deep oceans, however, where no light penetrates, microbes (e.g., bacteria) use chemosynthesis—chemical reactions involving inorganic materials like sulfur—to power the production of the organic compounds necessary for life. Such microbes drive key biogeochemical cycles that impact all life on earth. The primary causes of microbial mortality are viruses, which are the most abundant biological entities in the oceans. Yet, little has been known about their impact on chemosynthetic microbes in the dark oceans.
Now, recent work at the ALS microprobe beamline, Beamline 10.3.2, by Brandy Toner (University of Minnesota) in collaboration with Gregory Dick (University of Michigan), shows that the viruses infecting globally distributed sulfur-oxidizing bacteria in the deep sea carry bacterial genes for the oxidation of elemental sulfur. Although such observations are common in viruses that infect phytoplankton in the surface oceans, this represents the first instance of such a relationship in the dark oceans.
The results suggest that such viruses employ a novel strategy to trick the bacteria into utilizing their stored reserves of sulfur. Although the viruses themselves cannot use the sulfur, they likely supplement bacterial sulfur oxidation and then exploit the generated energy for viral replication. The findings implicate viruses as a previously unknown cog in the global sulfur cycle and will help researchers understand how biogeochemical cycles will respond to environmental change.
Work performed on ALS Beamline 10.3.2.
Citation: Karthik Anantharaman, Melissa B. Duhaime, John A. Breier, Kathleen A. Wendt, Brandy M. Toner, and Gregory J. Dick, “Sulfur Oxidation Genes in Diverse Deep-Sea Viruses,” Science 344, 757 (2014).