The Physiology and Biogeochemistry of SUP05

The SUP05 clade of gammaproteobacteria (Thioglobaceae) comprises both primary producers and primary consumers of organic carbon in the oceans. Host-associated autotrophs are a principal source of carbon and other nutrients for deep-sea eukaryotes at hydrothermal vents, and their free-living relatives are a primary source of organic matter in seawater at vents and in marine oxygen minimum zones. Similar to other abundant marine heterotrophs, such as SAR11 and Roseobacter, heterotrophic Thioglobaceae use the dilute pool of osmolytes produced by phytoplankton for growth, including methylated amines and sulfonates. Heterotrophic members are common throughout the ocean, and autotrophic members are abundant at hydrothermal vents and in anoxic waters; combined, they can account for more than 50% of the total bacterial community. Studies of both cultured and uncultured representatives from this diverse family are providing novel insights into the shifting biogeochemical roles of autotrophic and heterotrophic bacteria that cross oxic-anoxic boundary layers in the ocean.