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Organic matter degradation: Linking microbial identity to metabolic function

Institution: MPI Biogeochemistry
Biogeochemical Processes
Hans-Knoell-Str. 10
07754 Jena
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Telephone: +49 (0)3641/576130

Ashish Malik

Background and aim: The primary source of organic carbon to terrestrial ecosystem is from plants. There are several ways by which carbon enters the soil from vegetation; the below-ground process of rhizo-deposition contributing significantly. This process of soluble organic carbon input into the soil has not been sufficiently investigated. We aim to characterize the low molecular weight carbon (LMW-C) compounds in root exudates and link it to the microbial communities involved in its turnover.

Methodology: Our first strategy is to take advantage of natural-abundance differences in isotopes among substrates. In soils grown with C3 (δ13C ≈ -29‰) or C4 (δ13C ≈ -12‰) plants, the organic matter will be naturally labelled with its characteristic isotopic signature. Investigation of the dissolved organic carbon (DOC) from soils with C3 and C4 vegetation (rhizosphere and non-rhizosphere) for its stable isotope composition would help determine its source. This would be accomplished by size fractionation of the DOC and on-line δ13C measurements by HPLC-IRMS. Later we aim to develop a method for HPLC separation of RNA species and simultaneous on-line analysis of the separated molecules for carbon isotope ratios. Later microcosm experiments would be carried out monitoring the uptake of labelled LMW-C compounds fed into the soil using artificial roots and microdialysis systems. So our strategy is to combine stable isotope probing and metagenomics where incorporation of stable isotope from a labelled substrate is used to identify the function of microorganisms in the environment. With RNA as a biomarker; molecules with the incorporated labelled heavy isotope can thus be utilized not only to gain extensive phylogenetic information but also to link it with substrate utilization.

Perspective: The project would link rhizosphere microbial community to decomposition pathways of compounds in root exudates.



Home PhD projects Malik, Ashish: Understanding the mechanisms of organic matter degradation from black pelites