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| Titel |
"Death in soil" or what can we learn from groundwater for the genesis of soil organic matter |
| VerfasserIn |
M. Kaestner, A. Miltner, P. Bombach, B. Schmidt-Brücken |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250027774
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| Zusammenfassung |
| Soil microorganisms do not only catalyze the transformation of plant residues to soil organic
matter, but also serve as considerable carbon source for the formation of refractory soil
organic matter by providing cell fragments as structural interfacial surfaces in soil
systems.
After incubation of 13C-labeled Gram negative bacteria in soil for 224 days, we could
show that 44% of the bulk carbon remained in soil. 30 – 35 % of the remaining
bulk C from Gram negative microbial biomass was stabilized in non-living soil
organic matter (SOM). Surprisingly, the added labeled biomass proteins remained in
soil almost completely which clearly indicates the stabilization of proteins in cell
aggregations being more resistant to biodegradation than free proteins and amino
acids. Scanning electron micrographs of the soil showed very rarely intact cells but
highly abundant patchy organic cover material of 20 to 50 nm2 size on the mineral
surfaces.
A possible mechanism for this stabilization and the observed material could be found
by analyses of microbial communities and biofilms developing on Biosep? beads
within in situ microcosms exposed to contaminated aquifers. Scanning electron
micrographs of the developing biofilms on the beads showed the formation of such patchy
material found in the soil by fragmentation of empty bacterial cell envelopes (cell
walls) and all stages of decay. The fragmentation of these cell walls provided a
mechanistic explanation for the observed stabilisation, the genesis of SOM derived from
dead bacterial cells, and the enzyme activity always found associated to SOM. |
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