Award: OCE-1232840

Sulfur-oxidizing marine bacteria are ubiquitous in the ocean. They are of particular interest in upwelling regions, anoxic fjords and hydrothermal systems, where reduced sources of sulfur fuel carbon fixation and nitrogen loss. Metagenomic studies have identified an abundant group of sulfur-oxidizing bacteria with the genetic potential to regulate carbon and nitrogen cycling in these regions. However, this group has defied cultivation and their precise biogeochemical roles are unknown. We isolated the first cultured representatives from this group, sequenced their genomes and determined their growth requirements. We cultured one representative from Puget Sound ("Ca. Thioglobus singularis" strain PS1) and sequenced its genome to identify the metabolic adaptations that have enabled this group of sulfur-oxidizers to occupy the global ocean. Our results indicate that members of this group are streamlined marine mixotrophs that have the genetic potential to function as carbon fixing autotrophs and organic carbon consuming heterotrophs in seawater. We also cultured a representative from Effingham Inlet in British Columbia ("Ca. Thioglobus autotrophica" strain EF1) and sequenced its genome to identify the metabolic adaptations that have enabled this group of sulfur-oxidizers to occupy marine oxygen minimum zones. Our results indicate that members of this group are chemoautotrophic and have the genetic potential to fix carbon and respire nitrate (producing nitrite and a potent greenhouse gas, nitrous oxide). Carbon fixation and nitrogen reduction are important functions linking the oceans and the atmosphere. Evidence that abundant sulfur-oxidizing marine bacteria perform these functions suggests that sulfur-oxidizing marine bacteria have critical roles in regulating nutrients on Earth. Future studies will use data from this project to quantify the amount of carbon that is fixed from the atmosphere and the amount of nitrogen that is removed from the oceans by sulfur-oxidizing bacteria. Last Modified: 11/13/2015 Submitted by: Robert Morris