AUTHOR=Kalyuzhanaya Marina, Yang Song, Matsen Janet, Konopka Michael, Green-Saxena Abigail, Clubb Justin, Sadilek Martin, Orphan Victoria, Beck David TITLE=Global Molecular Analyses of Methane Metabolism in Methanotrophic Alphaproteobacterium, Methylosinus trichosporium OB3b. Part II. Metabolomics and 13C-Labeling Study JOURNAL=Frontiers in Microbiology VOLUME=4 YEAR=2013 URL=https://www.frontiersin.org/articles/10.3389/fmicb.2013.00070 DOI=10.3389/fmicb.2013.00070 ISSN=1664-302X ABSTRACT=In this work we use metabolomics and 13C-labeling data to refine central metabolic pathways for methane utilization in Methylosinus trichosporium OB3b, a model alphaproteobacterial methanotrophic bacterium. We demonstrate here that similar to non-methane utilizing methylotrophic alphaproteobacteria the core metabolism of the microbe is represented by several tightly connected metabolic cycles, such as the serine pathway, the ethylmalonyl-CoA (EMC) pathway, and the citric acid (TCA) cycle. Both in silico estimations and stable isotope labeling experiments combined with single cell (NanoSIMS) and bulk biomass analyses indicate that a significantly larger portion of the cell carbon (over 60%) is derived from CO2 in this methanotroph. Our13 C-labeling studies revealed an unusual topology of the assimilatory network in which phosph(enol) pyruvate/pyruvate interconversions are key metabolic switches. A set of additional pathways for carbon fixation are identified and discussed.