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| Titel |
From microbial biomass compounds to non-living soil organic matter - Microbial biomass as a significant source for soil organic matter formation |
| VerfasserIn |
A. Miltner, R. Kindler, C. Hoffmann-Jäniche, B. Schmidt-Brücken, M. Kästner |
| 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 |
250025694
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| Zusammenfassung |
| Soil organic matter is one of the most important pools of the global carbon cycle. Recently, it
has been suggested that microbial biomass is a significant source for the formation of
refractory organic matter. We tested the relevance of this source by incubation of soil with
13C-labeled Escherichia coli cells. We traced the labeled carbon in fatty acids and amino
acids, both in the microbial biomass and in the bulk soil. We also localized cells and their
debris by scanning electron microscopy. Although we could not detect any living cells after
100 days, about 50% of the carbon remained in the soil after 224 days. The amount of label in
the fatty acids indicated that microbial lipids were degraded faster than the bulk microbial
biomass. Their labeling pattern showed that they were redistributed from E. coli
to the microbial food web and from the living biomass to non-living soil organic
matter. In contrast, the label in the total amino acids did not decrease significantly
during incubation. Proteins are thus surprisingly stable in soil, but they also shifted
from microbial biomass to non-living soil organic matter. The scanning electron
micrographs showed only isolated intact microbial cells in our soil, but patches
of organic material of unknown origin which are about 20 - 50 nm2 in size were
quite abundant. Dying microbial cells therefore are a significant carbon source
for the formation of refractory organic material, but the morphology of the cells
changes during degradation, as cell structures cannot be found frequently in soils. |
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