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| Titel |
Organomineral interactions as an important mechanism for stabilisation of
bacterial residues in soil |
| VerfasserIn |
Anja Miltner, Jan Achtenhagen, Matthias Kästner |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250143778
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| Publikation (Nr.) |
 EGU/EGU2017-7531.pdf |
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| Zusammenfassung |
| Although plant material is the original input of organic matter to soils, microbial residues
have been identified to contribute to a large extent to soil organic matter. However, until now
it is unclear how microbial residues are stabilised in soil and protected from degradation. We
hypothesised that organomineral interactions, in particular encrustation by oxides, may play
an important role, which might vary depending on environmental conditions, e.g. redox
potential. Therefore we produced 14C-labelled Escherichia coli cells and cell envelope
fragments and coprecipitated these materials with Fe oxide or Al oxide. Mineral-free
(control) and mineral-encrusted bacterial residues were incubated for 345 days at 20˚ C
under either oxic or oxygen-limited conditions, and mineralisation was quantified by
scintillation counting of the CO2 produced during incubation. Oxygen limitation
was achieved by first exchanging the atmosphere in the incubation vessels with
dinitrogen gas. After 100 days of incubation, the anoxic treatments were waterlogged to
further decrease the redox potential, and after 290 days, glucose and nutrients were
supplied to all treatments in order to foster microbial activity and consumption of
electron acceptors. The mineralisation curves were fitted by double-exponential (0-100
days), first-order kinetic (100-290 days) and linear (290-345 days) models. The
model parameters were tested for significant differences between the treatments by
three-way ANOVA with post-hoc Bonferroni t-test. We found that encrustation by the
oxides significantly reduced mineralisation of the bacterial residues. This effect was
inversed by reductive dissolution of Fe oxides after substrate and nutrient addition to
the oxygen-limited treatments, suggesting a significant role of the encrustation in
stabilisation of the bacterial residues. We also observed that bacterial cell envelope
fragments were generally slightly more resistant to mineralisation than whole cells. The
results indicate that bacterial residues, in particular cell envelope fragments, may be
stabilised in soil by organomineral interactions as long as the minerals are stable in soil. |
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