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Manufacturing triple-isotopically labeled microbial necromass to track C, N and P cycles in terrestrial ecosystems
No full textThe functional relevance of microbial necromass in terrestrial biogeochemical cycles remains one of the unresolved mysteries of element cycling in ecosystems, especially considering the high microbial abundance and turnover in soil. We therefore established a protocol to manufacture multi-isotope (14C, 15N and 33P) labeled microbial necromass to comprehensively track the turnover of microbial necromass elements within element cycles. This protocol encompasses the i) microbial cultivation of Pseudomonas kilonensis ACN4 (Gram-negative) and Bacillus licheniformis DSM13 (Gram-positive) on labeled minimal medium as well as fungal cultivation of Hypsizygus tessulatus on a complex yeast medium, ii) quantification of radio- (14C, 33P) and stable (15N) isotope incorporation as well their cellular pool partitioning, and iii) determination of element and tracer isotope uptake efficiency. We achieved 1 g of bacterial biomass per liter minimum medium within 24 h and 2.9 g l-1 fungal biomass in complex medium within 18 d. This production rate enabled us to produce more than 100 g of necromass within only one half-life time of 33P, including post-harvest processing. Isotope uptake and incorporation for 33P ranged from 10 to 73%, for 15N from 24 to 52%, and for 14C from 12 to 23%. Each of the cultivated species showed individual patterns of tracer element uptake. The nutritional value of the carbon- (C), nitrogen- (N) and phosphorus- (P) labeled microbial necromass was characterized by a water-based, necromass speciesspecific partitioning scheme with subsequent elemental analysis of the pools. We separated Gram-negative, Gram-positive and fungi’s cellular pools to characterize element and tracer partitioning among dissolved versus particulate fractions. That is essential because these properties subsequently affect the respective pool's availability for ecosystem nutrition. Our procedure allows a defined production of microorganism-based necromass, enabling versatile use to determine necromass-related nutrient fluxes in terrestrial ecosystem studies
Subsoil biogeochemical properties induce shifts in carbon allocation pattern and soil C dynamics in wheat
No full text
Arbuscular mycorrhiza enhances rhizodeposition and reduces the rhizosphere priming effect on the decomposition of soil organic matter
No full textRedundancy of microbial P mobilization in beech forest soils with contrasting P stock: A microbial dilution experiment
No full textRoot-o-Mat: A novel tool for 2D image processing of root-soil interactions and its application in soil zymography
No full textExtracellular enzyme activity and stoichiometry: The effect of soil microbial element limitation during leaf litter decomposition
No full textCorrection to: Size matters: biochemical mineralization and microbial incorporation of dicarboxylic acids in soil
Full text linkThe transformation and turnover time of medium- to long-chain dicarboxylic acids (DCA) in soil is regulated by microbial uptake and mineralization. However, the chain length of n-alkyl lipids may have a remarkable influence on its microbial utilization and mineralization and therefore on the formation of stable soil organic carbon from e.g. leave- needle- and root-derived organic matter during decomposition. To investigate their size dependent mineralization and microbial incorporation, four DCA of different chain lengths (12–30 carbon atoms), that were 13C labeled at each of their terminal carboxylic groups, were applied to the Ah horizon of a Fluvic Gleysol. Incorporation of 13C into CO2 and in distinct microbial groups classified by phospholipid fatty acid (PLFA) analysis was investigated. Mineralization of DCA and incorporation into PLFA decreased with increasing chain length, and the mineralization rate was highest during the first days of incubation. Half-life time of DCA carbon in soil increased from 7.6 days for C12 DCA to 86.6 days for C18 DCA and decreased again to 46.2 days for C22 DCA, whereas C30 DCA had the longest half-life time. Rapid and efficient uptake of C12 DCA as an intact molecule was observable. Gram-negative bacteria incorporated higher amounts of DCA-derived 13C compared to other microbial groups, especially compared to actinomycetes and fungi during the first phase of incubation. However, the incorporation of C12 DCA derived 13C into the PLFA of actinomycetes, and fungi increased steadily during the entire incubation time, suggesting that those groups take up the 13C label from necromass of bacteria that used the C12 DCA for formation of their lipids before
Size matters: biochemical mineralization and microbial incorporation of dicarboxylic acids in soil
Full text linkAbstract
The transformation and turnover time of medium- to long-chain dicarboxylic acids (DCA) in soil is regulated by microbial uptake and mineralization. However, the chain length of n-alkyl lipids may have a remarkable influence on its microbial utilization and mineralization and therefore on the formation of stable soil organic carbon from e.g. leave- needle- and root-derived organic matter during decomposition. To investigate their size dependent mineralization and microbial incorporation, four DCA of different chain lengths (12–30 carbon atoms), that were
13
C labeled at each of their terminal carboxylic groups, were applied to the Ah horizon of a Fluvic Gleysol. Incorporation of
13
C into CO
2
and in distinct microbial groups classified by phospholipid fatty acid (PLFA) analysis was investigated. Mineralization of DCA and incorporation into PLFA decreased with increasing chain length, and the mineralization rate was highest during the first days of incubation. Half-life time of DCA carbon in soil increased from 7.6 days for C
12
DCA to 86.6 days for C
18
DCA and decreased again to 46.2 days for C
22
DCA, whereas C
30
DCA had the longest half-life time. Rapid and efficient uptake of C
12
DCA as an intact molecule was observable. Gram-negative bacteria incorporated higher amounts of DCA-derived
13
C compared to other microbial groups, especially compared to actinomycetes and fungi during the first phase of incubation. However, the incorporation of C
12
DCA derived
13
C into the PLFA of actinomycetes, and fungi increased steadily during the entire incubation time, suggesting that those groups take up the
13
C label from necromass of bacteria that used the C
12
DCA for formation of their lipids before.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659Christian-Albrechts-Universität zu Kiel 50110000286
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