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

Abstract

The microbial contribution to soil organic matter (SOM) has recently been shown to be much larger than previously thought and thus its role in carbon sequestration may also be underestimated. In this study we employ (13)C ((13)CO₂) to assess the potential CO₂ sequestration capacity of soil chemoautotrophic bacteria and combine nuclear magnetic resonance (NMR) with stable isotope probing (SIP), techniques that independently make use of the isotopic enrichment of soil microbial biomass. In this way molecular information generated from NMR is linked with identification of microbes responsible for carbon capture. A mathematical model is developed to determine real-time CO₂ flux so that net sequestration can be calculated. Twenty-eight groups of bacteria showing close homologies with existing species were identified. Surprisingly, Ralstonia eutropha was the dominant group. Through NMR we observed the formation of lipids, carbohydrates, and proteins produced directly from CO₂ utilized by microbial biomass. The component of SOM directly associated with CO₂ capture was calculated at 2.86 mg C (89.21 mg kg(-1)) after 48 h. This approach can differentiate between SOM derived through microbial uptake of CO₂ and other SOM constituents and represents a first step in tracking the fate and dynamics of microbial biomass in soil.

Autotrophic fixation of geogenic CO<sub>2</sub> by microorganisms contributes to soil organic matter formation and alters isotope signatures in a wetland mofette

“…A contribution of phototrophic and chemoautotrophic microorganisms to SOM has been demonstrated already by other studies (Hart et al, 2013;Yuan et al, 2012), but solely for top soils. Wu et al (2014Wu et al ( , 2015 investigated soil depth profiles up to 15 cm depth , but found no significant incorporation below 5 cm depth in upland and paddy soils under not manipulating experimental conditions, like illumination.…”

“…Direct uptake of CO 2 into microbial biomass (MB) and soil organic matter (SOM) by photoautotrophic and chemoautotrophic organisms has been measured in paddy rice and agricultural upland soils (Liu and Conrad, 2011;Wu et al, 2015Wu et al, , 2014 as well as under manipulating experimental conditions, such as H 2 amendment (Stein et al, 2005) or addition of reduced sulfur compounds (Hart et al, 2013). Autotrophic acetogenic organisms, using the Wood-Ljungdahl pathway for CO 2 fixation, are important groups in wetland and forest soils (Küsel and Drake, 1995;Ye et al, 2014).…”

Community Structure and Soil pH Determine Chemoautotrophic Carbon Dioxide Fixation in Drained Paddy Soils

“…eutropha, which is well-known for its contribution to carbon sequestration in soil through the production of polyhydroxyalkanoates. 35 On the basis of the kinetic properties of the RubisCO forms, it is generally believed that form II RubisCO favors high-CO 2 (1.5%) and low-O 2 conditions while form I RubisCO is more active under aerobic conditions and in low-CO 2 environments. 33 The multiple RubisCO gene sets can help microorganisms to survive in a dynamic environment such as paddy soils, with respect to the switching between aerobic and anaerobic conditions.…”

Large perturbations in CO2 flux and subsequent chemosynthesis are induced in agricultural soil by the addition of elemental sulfur

“…Previously, we showed that the addition of thiosulfate to soils resulted in an order of magnitude increase in the uptake of CO 2 by chemoautotrophs 12, 13 . Thiosulfate acts as an electron donor and provides the energy for a large increase in CO 2 uptake.…”