These state of the art approaches in isotope and environmental ecology are essential to link microbiological ecology to biogeochemistry.
Biomarkers are also used to probe the origin and alteration degree of soil organic matter. For example, the biomarker potential of root and shoot derived aliphatic macromolecules (suberin and cutin) is currently under investigation in order to trace the origin of soil organic carbon. The acid-to-aldehyde ratio of soil lignin structures is a function of its alteration degree, which can be characteristic of given soil formations and thereby help determine the origin of SOM in sedimentary systems.
Research theme 4 supports activities on soil biomarkers aimed at unravelling the microbial transformations and decomposition processes affecting soil organic matter, as well as tracing its origin in terms of plant species and organ type.
Theme 1: Molecular composition and turnover of soil organic matter
Theme 2: Plant molecular structures as drivers of C stabilisation in soils
Theme 3: Fire transformations of plant and soil molecular structures
Theme 5: Dissolved organic molecules in soils: origin, functionality and transport
Theme 4: Molecular markers in soils
Biomarkers are a powerful tool to unravel the processes that govern the soil organic matter transformation in soils. Among these processes, microbial transformations and activities are central. Knowing which microorganisms are active is indispensable for biogeochemical research.
Since most microorganisms cannot be cultured (easily) in the laboratory, alternative molecular techniques have been developed, based on observations that specific biomarker molecules, characteristic for a specific type of microorganism present in an ecosystem, can be isolated and quantified. Linking these molecular biomarker techniques with component specific stable isotope techniques (e.g. GC-c-IRMS and LC-c-IRMS) provide additional advantages. Via stable isotopes probing (SIP) labeled substrates can be introduced in an ecosystem e.g. via (13CO2) pulse labeling of the vegetation. Transfer of 13C via root exudates to active microorganisms permits to identify metabolically active microorganisms via the isotopic composition of their respective biomarkers.
Because of the great structural diversity and specificity of the phospholipid fatty acid (PLFA) building blocks of cell membranes and because of their instability after necrosis, PLFA’s are an ideal proxy for the microbial biomass. Cell walls of fungi, bacteria and actinomycetes are partially constructed of amino sugars (AS) which can be used as biomarkers for microbial necromass. The relative and absolute amounts of AS in soil, together with their individual δ13C values can be used to determine turnover times and contribution to C-sequestration of microbial soil communities.