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| Titel |
Microbial utilization of low molecular weight organic substrates in soil depends on their carbon oxidation state |
| VerfasserIn |
Anna Gunina, Andrew Smith, Davey Jones, Yakov Kuzyakov |
| 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 |
250139362
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| Publikation (Nr.) |
 EGU/EGU2017-2589.pdf |
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| Zusammenfassung |
| Removal of low molecular weight organic substances (LMWOS), originating from plants and
microorganisms, from soil solution is regulated by microbial uptake. In addition to the
concentration of LMWOS in soil solution, the chemical properties of each substance (e.g. C
oxidation state, number of C atoms, number of -COOH groups) can affect their uptake and
subsequent partitioning of C within the soil microbial community. The aim of this study
was to trace the initial fate of three dominant classes of LMWOS in soil (sugars,
carboxylic and amino acids), including their removal from solution and utilization by
microorganisms, and to reveal the effect of substance chemical properties on these
processes.
Soil solution, spiked at natural abundance levels with 14C-labelled glucose, fructose,
malate, succinate, formate, alanine or glycine, was added to the soil and 14C was traced in the
dissolved organic carbon (DOC), CO2, cytosol and soil organic carbon (SOC) over 24
hours. The half-life time of all LMWOS in the DOC (T1 ∕2−solution) varied between
0.6-5.0 min showing extremely fast initial uptake of LMWOS. The T1 ∕2−solution of
substances was dependent on C oxidation state, indicating that less oxidized organic
substances (with C oxidation state ”0”) were retained longer in soil solution than
oxidized substances. The LMWOS-C T1 ∕2−fast, characterizing the half-life time
of 14C in the fast mineralization pool, ranged between 30 and 80 min, with the
T1 ∕2−fast of carboxylic acids (malic acid) being the fastest and the T1 ∕2−fast of amino
acids (glycine) being the slowest. An absence of correlation between T1 ∕2−fast
and either C oxidation state, number of C atoms, or number of -COOH groups
suggests that intercellular metabolic pathways are more important for LMWOS
transformation in soil than their basic chemical properties. The CO2 release during LMWOS
mineralization accounted for 20-90% of 14C applied. Mineralization of LMWOS was the
least for sugars and the greatest for carboxylic (formic) acids, whereas the 14C
incorporations into cytosol and SOC were opposite. The portion of LMWOS mineralized
to CO2 increased with their C oxidation state corresponding to the decrease of C
incorporated into the cytosol and SOC pools. The ratio of 14C incorporated into
cytosol to 14C incorporated into CO2 pool ranged between 0.03 and 1.19, being the
lowest for carboxylic acids and highest for sugars, and decreased with substances C
oxidation state. Thus, the C oxidation state is one of the crucial parameter of LMWOS
determining their partitioning between two main C fluxes: mineralization and microbial
stabilization/immobilization. Our data suggests that the uptake of common LMWOS from
soil solution by microorganisms and final LMWOS-C partitioning within microbial biomass
may be possible to predict from the physicochemical properties of the substance. |
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