@article{10.1371/journal.pone.0023973, doi = {10.1371/journal.pone.0023973}, author = {Sun, Jing AND Steindler, Laura AND Thrash, J. Cameron AND Halsey, Kimberly H. AND Smith, Daniel P. AND Carter, Amy E. AND Landry, Zachary C. AND Giovannoni, Stephen J.}, journal = {PLOS ONE}, publisher = {Public Library of Science}, title = {One Carbon Metabolism in SAR11 Pelagic Marine Bacteria}, year = {2011}, month = {08}, volume = {6}, url = {https://doi.org/10.1371/journal.pone.0023973}, pages = {1-12}, abstract = {The SAR11 Alphaproteobacteria are the most abundant heterotrophs in the oceans and are believed to play a major role in mineralizing marine dissolved organic carbon. Their genomes are among the smallest known for free-living heterotrophic cells, raising questions about how they successfully utilize complex organic matter with a limited metabolic repertoire. Here we show that conserved genes in SAR11 subgroup Ia (Candidatus Pelagibacter ubique) genomes encode pathways for the oxidation of a variety of one-carbon compounds and methyl functional groups from methylated compounds. These pathways were predicted to produce energy by tetrahydrofolate (THF)-mediated oxidation, but not to support the net assimilation of biomass from C1 compounds. Measurements of cellular ATP content and the oxidation of 14C-labeled compounds to 14CO2 indicated that methanol, formaldehyde, methylamine, and methyl groups from glycine betaine (GBT), trimethylamine (TMA), trimethylamine N-oxide (TMAO), and dimethylsulfoniopropionate (DMSP) were oxidized by axenic cultures of the SAR11 strain Ca. P. ubique HTCC1062. Analyses of metagenomic data showed that genes for C1 metabolism occur at a high frequency in natural SAR11 populations. In short term incubations, natural communities of Sargasso Sea microbial plankton expressed a potential for the oxidation of 14C-labeled formate, formaldehyde, methanol and TMAO that was similar to cultured SAR11 cells and, like cultured SAR11 cells, incorporated a much larger percentage of pyruvate and glucose (27–35%) than of C1 compounds (2–6%) into biomass. Collectively, these genomic, cellular and environmental data show a surprising capacity for demethylation and C1 oxidation in SAR11 cultures and in natural microbial communities dominated by SAR11, and support the conclusion that C1 oxidation might be a significant conduit by which dissolved organic carbon is recycled to CO2 in the upper ocean.}, number = {8}, }