Abstract
Linking microbial metabolomics and carbon sequestration in the ocean via refractory organic molecules has been hampered by the chemical complexity of dissolved organic matter (DOM). Here, using bioassay experiments and ultra-high resolution metabolic profiling, we demonstrate that marine bacteria rapidly utilize simple organic molecules and produce exometabolites of remarkable molecular and structural diversity. Bacterial DOM is similar in chemical composition and structural complexity to naturally occurring DOM in sea water. An appreciable fraction of bacterial DOM has molecular and structural properties that are consistent with those of refractory molecules in the ocean, indicating a dominant role for bacteria in shaping the refractory nature of marine DOM. The rapid production of chemically complex and persistent molecules from simple biochemicals demonstrates a positive feedback between primary production and refractory DOM formation. It appears that carbon sequestration in diverse and structurally complex dissolved molecules that persist in the environment is largely driven by bacteria.
Highlights
Linking microbial metabolomics and carbon sequestration in the ocean via refractory organic molecules has been hampered by the chemical complexity of dissolved organic matter (DOM)
The chemical complexity of bacterial DOM was compared with DOM isolated from the surface Atlantic Ocean and analysed under the same experimental conditions[13]
Bacterial DOM did not reflect the same extent of structural space coverage as surface Atlantic DOM (Fig. 4c), but the chemical complexity generated by bacterial metabolism provides novel insights about the mechanisms shaping the complexity of DOM
Summary
Linking microbial metabolomics and carbon sequestration in the ocean via refractory organic molecules has been hampered by the chemical complexity of dissolved organic matter (DOM). The chemical composition and biological reactivity of DOM are modified during microbial utilization and processing, resulting in small dissolved molecules (o10 kDa) that are very resistant to further microbial alteration and consumption[3] Microbial production of this refractory DOM contributes substantially to carbon sequestration in the ocean, a process recently termed the microbial carbon pump[3,4]. At the end of the 29-day incubations, DOM was isolated by solid-phase extraction (SPE) and analysed by Fourier transform ion cyclotron resonance mass spectrometry[12] and high-field nuclear magnetic resonance spectroscopy (NMR)[13] These complementary untargeted analyses provide novel insights into the biological generation of chemical complexity and the molecular imprint of microbes on DOM in the ocean
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