Undocumented Potential For Primary Productivity In A Globally-Distributed Bacterial Photoautotroph

Abstract

Aerobic anoxygenic phototrophs (AAnPs) are common in the global oceans and are associated with photoheterotrophic activity. To date, AAnPs have not been identified in the surface ocean that possess the potential for carbon fixation. Using the Tara Oceans metagenomic dataset, we have reconstructed high-quality genomes of four bacteria that possess the genomic potential for anoxygenic phototrophy, carbon fixation via the Calvin-Benson-Bassham cycle, and the oxidation of sulfite and thiosulfate. Forming a monophyletic clade within the Alphaproteobacteria and lacking cultured representatives, the organisms compose minor constituents of local microbial communities (0.1-1.0%), but are globally distributed, present in multiple samples from the North Pacific, Mediterranean Sea, the East Africa Coastal Province, and the South Atlantic. These organisms represent a shift in our understanding of microbially-mediated photoautotrophy in the global oceans and provide a previously undiscovered route of primary productivity.