BayCEER Workshop 2025

Compound-specific stable isotope analysis of individual amino sugars – method development and first insights into mean residence times of fungal and bacterial necromass

P 12 in Posters

Soil microbes are known to mineralize and transform soil organic matter (SOM). The remaining microbial necromass is known to contribute about 40 % to the total SOM pool (e.g. Liang et al, 2018). Some of these microbes preferentially mineralize labile OM while others may feed on more stable materials. Especially the decomposition of stable OM forms such as lignin is known to be achieved rather by fungi than by bacteria. We hypothesized that we could show this via a novel technique to isolate and analyze individual amino sugars (this is muramic acid for bacteria and glucosamine for fungi) for their d13C composition. In this poster we show the first analytical steps into isolation of fungal necromass markers muramic acid and glucosamine from soil using HPLC, a fractionation sampling device and subsequent d13C analysis with laser-ablation IRMS.  

This method allows detecting the mean residence time of bacterial and fungal necromass in agricultural soil, e.g. in C3/C4 vegetation change experiments and stable isotope labeling.  

 

Keywords: Microbial necromass, Amino sugars, Soil Organic Matter, d13C, HPLC