Fig. 2: Metabolomic evidence for anoxic degradation of a model polyphenol in soil.
From: Decrypting bacterial polyphenol metabolism in an anoxic wetland soil
a Model CT polymers have an average degree of polymerization of 16, with repeating epicatechin (blue) units capped with a terminal catechin (magenta). Depolymerization breaks the interflavan bonds of the polymer backbone, generating smaller sized oligomers and monomers. These can be further transformed, by biotic or abiotic processes, to lower molecular weight phenolic compounds. b Kendrick mass defect (KMD) hex plots for the peaks detected in replicate C of biologically-active (top) and autoclaved (bottom) CT-amended microcosms. KMD is given relative to (epi)catechin. Hex plots divide plot area into equal size hexagons, and hexagons are colored according to the number of data points that fall in that area. At left, peak information that enabled oligomer assignments is shown by colors where 13Co (orange) and 13Ce (green) denote doubly-charged compounds containing odd and even numbers of 13C, respectively (see Supplementary Fig. 4 for detailed examples). Colored rectangles are shown around regions where CT oligomers (blue) and monomers/dimers (pink) and their derived compounds are expected to occur, with key regions highlighted in purple. Corresponding colored numbers indicate oligomer sizes: monomer (1), dimer (2), trimer (3), tetramer (4), pentamer (5), and hexamer (6) peaks. Kendrick plots for all replicates at all timepoints are found in Supplementary Fig. 6A–C. c–f Metabolites detected via LC–MS can be organized into c CT C15 monomers (epicatechin, catechin), d other C15 flavonoids (quercetin), e C6-C3 phenolic compounds, and f C6-C2 phenolic compounds. Metabolite dynamics are shown with lines indicating average peak area (n = 3 individual biological replicates) for CT (purple) microcosms, and shaded areas the 95% confidence interval with individual data points plotted. Dotted lines show signal from autoclaved CT-amended soil control. Orange circles indicate timepoints at which active soil signal significantly differed from autoclaved soil signals (LIMMA, p < 0.05, log2FC > 1.5, see Supplementary Data 1 for exact p-values). Vertical gray lines mark day 10. In the illustration of the monomer structure in (c), red letters label flavonoid rings, and red numbers correspond to C-ring position.
