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SPP 1090 AG 2: Mass balance of microbial biomass contribution to the formation of refractory soil organic matter using isotope tracer techniques – (cells, cell components,CO2, and NH4)

Project

Environment and ressource management

This project contributes to the research aim ' Environment and ressource management'. Which funding institutions are active for this aim? What are the sub-aims? Take a look:
Environment and ressource management


Project code: DFG SPP 1090
Contract period: 01.01.2000 - 01.01.2006
Purpose of research: Basic research

In general, a considerable amount of carbon is converted to biomass of bacteria during microbial turnover of organic compounds. After death of the cells, this biomass is subject to biodegradation by other microorganisms or fragments of the mortal cells are fixed within the soil organic matter (SOM). Thus, microbial biomass contributes substantially to the formation of refractory soil organic matter. Using tracer compounds labeled with isotopes, the experiments are focused on the microbial turnover rates and the formation of humic substances derived from bacterial biomass, fractionated cell components, and from mineralization products such as CO2 and NH4. The transformation of isotopically labeled constituents of bacterial biomass (14C; 13C; 15N) will be analysed in bioreactors with model soils of the research program. The residual and fixed products of the labeled biomass will be balanced in different fractions of humic substances and particle sizes and will be further examined with isotope and structure analytical methods. Thus, the material contribution of microbial biomass to the formation of humic substances in soil can be balanced and the conversion factors and rates of the carbon and nitrogen distribution can be estimated. Results of preliminary experiments show evidence that carbon from CO2 contributes significantly to the formation of SOM. This may give rise to a re-evaluation of tracer experiments concerning the formation of bound residues from pesticide and xenobiotic compounds. A second step of the experiments will develop methods for the evaluation of the structure and function of the biopolymers fixed to the organic soil matrix. Special focus will be directed to the fixation of cell wall components, structural proteins and nucleic acids.

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