The unknown soil microbial stoichiometry and its potential use

Funded by German Research Foundation (DFG) • 2023-2026

The soil microbial community provides important ecosystem services and is intergral part of soil health and fertility. A microbial cell consists of biomolecules comprising the structural elements C, H, O, N, P, and S. Physiological and structural stability is granted by the ionic elements K, Na, Cl, Ca, and Mg. For fulfilling specific functions proteins like enzymes contain the proteinogenic metals Mg, Fe, Zn, Cu, Mn, and Mo. Depending on the kind of organism or the environmental conditions further elements can play specific roles like Se, Co, Ni, W, B, or Si. From the level of single cells to the whole community, sets of elements can be recognised, which are needed for growth and maintenance of the soil microbial biomass and the single processes of the ecosystem services ( However, the ratio of soil microbial biomass C to any other element, i.e. the stoichiometry, needed for running these processes is not known.


Determination of soil microbial biomass elements was restricted to C, N, P, S, and K and for the C:N:P ratio a relative homeostatic value has been found. A protocol developed in the Soil ionoMICS project (see below) enables now determining further microbial biomass elements ( Using soils, which by long-term fertilisation treatments differ in their nutritional status, the project aims at finding which elements behave homeostatic or plastic. We want to link the bioavailable elements and the soil microbial biomass elements to functions like enzyme activities and to the abundance of functional genes coding for metalloproteins. The grand goal is to find out whether the knowledge of soil bioavailable elements and microbial biomass stoichiometry can be used to enhance microbial growth and ecosystem services by addition of elements in limitation.