13C-Isotopomer-based metabolomics of microbial groups isolated from two forest soils |
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Authors: | Teresa W-M Fan Jeffrey A Bird Eoin L Brodie Andrew N Lane |
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Institution: | (1) Center for Regulatory and Environmental Analytical Metabolomics (CREAM), Department of Chemistry, University of Louisville, 2210 S. Brook St., Belknap Research Building, Rm 348, Louisville, KY 40208, USA;(2) James Graham Brown Cancer Center, University of Louisville, Louisville, KY 40202, USA;(3) School of Earth and Environmental Sciences, Queens College, City University of New York, Flushing, NY 11367, USA;(4) Earth Sciences Division, Ecology Department, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA |
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Abstract: | Soil microorganisms are the primary mediators of organic matter decomposition and humification processes in soil, which represent
a critical C flux in the global C cycle. Little is known about how soil microbes regulate carbon cycling including the contribution
of their own biomass to stable soil organic matter. A comprehensive understanding of microbial composition is a first step
to unraveling microbial regulation of soil humification processes. For this purpose, we isolated 23 microbial strains representing
four major groups (Gram (+) bacteria, Gram (−) bacteria, Actinobacteria, and Fungi) from a temperate and a tropical forest
soil. The microbial isolates were cultured with uniformly 13C-labeled glucose as the C source such that all biochemical components synthesized from glucose were 13C labeled. This approach enabled field mesocosm experiments on tracking microbial decomposition, while facilitating solution-
and solid-state NMR analysis of microbial composition. Polar and lipid extracts of labeled biomass of the four microbial groups
from the two forest sites were profiled by 2D NMR methods, including high-resolution heteronuclear single quantum coherence
spectroscopy and HCCH-total correlation spectroscopy. This 13C labeling approach also enabled the analysis of intact biomass by 2D solid-state 13C–13C correlation spectroscopy. Distinction between microbial groups and sites was observed in the polar and lipophilic metabolite
profiles. Dominant differences could also be related to the capacity for lipid β-oxidation or adaptation to desiccation. Solid-state
NMR further revealed differential synthetic capacity for glycolipids among groups. This technology coupled with 13C metabolite profiling should facilitate future functional annotation of indigenous microbial genomes. |
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Keywords: | 2D solution-state NMR 2D solid-state 13C NMR Gram negative bacteria Gram positive bacteria Actinobacteria Fungi |
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