2-P2: TherMic II

Thermodynamics of microbial turnover of organic compounds in soil – matter and energy fluxes under varying redox conditions, biomass-substrate ratios, and availability of biomass building blocks

Carbon (C) and energy (E) fluxes during SOM turnover are closely related, both depend on environmental conditions and resource availability. In the second phase of SoilSystems, we will focus on the role of redox conditions, biomass-substrate ratios and availability of biomass building blocks for the link between C and E fluxes. Hypotheses and approaches:
(1) Terminal electron acceptor availability strongly affects Gibbs energy release during mineralisation of a substrate and thus the link between C and E flux. This will be tested in soil incubation experiments tracing the fate of cellobiose at oxic, anoxic and alternating redox conditions.
(2) The availability of biomass building blocks modifies the relation between C and E fluxes as directly utilising a substrate as a biomass building block will reduce the energy required for biomolecule synthesis. We will therefore conduct incubation experiments varying the availability of biomass building blocks (e.g tryptophan) relative to cellobiose and test how C and E fluxes are affected.
(3) The abundance of active microorganisms (relative to substrate) does not only alter substrate degradation kinetics, but also has an effect on C and E balances. This will be investigated in incubation experiments at different biocatalyst/substrate ratios.
(4) We need to further develop the theoretical framework for thermodynamic assessment of soil processes. We will perform thermodynamic calculations and modelling. In particular, we will explore how we can proceed from the enthalpy measured by calorimetry to Gibbs energy, the driving force of soil processes. TherMic-II will additionally contribute to joint activities of SoilSystems such as an interlaboratory comparison to reveal variability of calorimetric data and the joint experiment E-ComPLEX studying the C and E fluxes of selected substrates with different combustion enthalpies and metabolic functions.  

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Link to English scientific abstract
Link to German scientific abstract

Link to project in the 1^st phase

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Research Team