Tracking the Fate of Microbially Sequestered Carbon Dioxide in Soil Organic Matter

摘要

The microbial contribution to soil organic matter (SOM) hasrnrecently been shown to be much larger than previously thought and thus itsrnrole in carbon sequestration may also be underestimated. In this study wernemploy ~(13)C(~(13)CO_2) to assess the potential CO_2 sequestration capacity of soilrnchemoautotrophic bacteria and combine nuclear magnetic resonance (NMR)rnwith stable isotope probing (SIP), techniques that independently make use ofrnthe isotopic enrichment of soil microbial biomass. In this way molecularrninformation generated from NMR is linked with identification of microbesrnresponsible for carbon capture. A mathematical model is developed torndetermine real-time ,CO_2 flux so that net sequestration can be calculated.rnTwenty-eight groups of bacteria showing close homologies with existingrnspecies were identified. Surprisingly, Ralstonia cutropha was the dominantrngroup. Through NMR we observed the formation of lipids, carbohydrates, andrnproteins produced directly from CO_2 utilized by microbial biomass. The component of SOM directly associated with CO_2rncapture was calculated at 2.86 mg C (89.21 mg kg~(-1)) after 48 h. This approach can differentiate between SOM derived throughrnmicrobial uptake of CO_2 and other SOM constituents and represents a first step in tracking the fate and dynamics of microbialrnbiomass in soil.