Saliva contains enzymes and attaches them to our food in the mouth. Extracellular polymeric substances (EPS for short), which are also formed in the soil by microorganisms, i.e. bacteria and fungi, have a similar function. Microorganisms and EPS form so-called biofilms - structures that adhere to the soil surface - which are vital for the survival of microbes and valuable for soils themselves: They make them more stable and resistant to environmental stresses such as drought, flooding or strong winds.

Galactosamine has often been detected in arable soils. There, this amino sugar is produced exclusively by microorganisms. However, it is not known what function this substance has for the microorganisms. The aim of the current project at the University of Kassel is now to find out whether it is an indicator for the presence of biofilms in soils. Rebeca Leme Oliva, doctoral student and research assistant at the Department of Ecological Plant Nutrition, is carrying out the corresponding research project. She is being supervised by the retired professor and former head of the Department of Soil Biology and Plant Nutrition, Prof. Dr. Rainer Georg Jörgensen. In order to get to the bottom of the connection between galactosamine and EPS, Oliva is conducting a series of experiments in which she exposes the soil to various substrates.

The first experiments took place in the laboratory under controlled conditions and have already been completed. Here, Oliva investigated the formation of EPS by fungi and bacteria and analyzed the extent to which the components of EPS change under different conditions.

Oliva is currently working with arable soil. She is adding easily or poorly degradable carbon to the soil and analyzing how it is processed in the soil. Since EPS, as already mentioned, offers important benefits to the soil, it is crucial to know how, when and which forms of biofilms form in it. "Investigating this system and producing EPS in an organic way, for example without fertilizer, would have positive effects for agriculture, as the soil could be prepared ecologically and specifically for adverse conditions," emphasizes Oliva.

The research project has been running since the beginning of 2022 and is a sub-project of the overarching DFG-funded project "System ecology of soils - the microbiome and boundary conditions modulate energy discharge", in which several German universities are participating. Its aim is to gain a better understanding of how soil systems function. Each of the sub-projects deals with a different component or characteristic of the soil, but all projects use the same soils to ensure comparability.

Contact:

Rebeca Leme Oliva
University of Kassel
Department of Ecological Plant Nutrition
Phone: +49 5542 981518
E-mail: rebeca.oliva[at]uni-kassel[dot]de