Labor für Radioisotope

Development of an advanced 33P-PLFA method:


A new and significant improvement of 33P-PLFA analysis was established to quantify P in microbial biomass and functional groups. The new method combines the classical phospholipid fatty acid (PLFA) analysis via gas chromatography mass spectrometry (composition of the microbial community) with 33P uptake and incorporation in the same sample. This enables to link changes in 33P fluxes into microbial biomass to changes in microbial community structure in soils in situ. It offers the possibility to link annual/seasonal dynamics of microbial P uptake and incorporation to annual/seasonal variations in microbial community structure.


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Fig.1: Scheme of a phospholipid molecule with the head group bearing information on 33P uptake and the fatty acid tails, indicative for the microbial Group

Microcosm experiment about P heterogeneity to study root growth as well as root and microbial mobilization of Fe33PO4

A rhizotron experiment was conducted to investigate the P uptake strategies of plants and microorganisms. F. sylvatica-bearing rhizoboxes were labeled with increasingly coarse spatial P patterns using 33P-Iron(III)phosphate to study the effects of spatial P heterogeneity in soil on plant and microbial P acquisition. P imaging and zymography were used to link enzyme activities with 33P uptake over the course of 3 months. Plant 33P uptake and localization in plant components were measured after termination of the experiment. P fluxes into the soil and specific microbial community structures were tracked by 33P-PLFA.


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Fig. 2: Left: Soil solution sampling by micro suction cups from three rhizotrones simultaneously; right: Acidic phosphatase zymography from beech roots in a rhizotrone. Photos: J.C. Mendez