Effect of soil microbial diversity on the efficiency of plant microbe symbiosis

Root-associated bacterial communities are important drivers of plant health and productivity.
Plants are closely connected to soil microorganisms. They excrete nutrients and other compounds via roots (“exsudates”) to select for specific useful communities of microorganisms in their rhizosphere. In return, the microorganisms promote plant growth by mobilizing nutrients from organic matter in the soil, by producing plant hormones or by suppressing plant pathogens.
One important function of plant associated bacteria is the activation of plant defenses, which leads to a stronger and more efficient defense response of the plant in the presence of pathogens.
In my project I want to investigate whether diverse bacterial communities are advantageous for the activation of plant defenses and consequently for the prevention of plant diseases. I will inoculate plants with controlled bacterial communities at different levels of diversity and measure the activation of plant defense genes. In addition I will examine bacterial metabolites which are responsible for an elevated immune reaction.

Furthermore, I want to investigate the effect of the diversity of bacterial communities on other symbionts of the plant, such as rhizobia and mycorrhizcal fungi (AMF).
The soil is inhabited by highly diverse microbial communities and understanding the importance of this diversity on microbial processes is crucial to predict and manipulate their properties. Moreover, the results of my work are important for the development of environmental friendly strategies for the protection of agricultural plants against diseases.

Master thesis: Effect of the diversity of rhizosphere bacteria on N uptake of Arabidopsis thaliana

In my master thesis I took a look at the effect of the diversity of bacterial communities on the mobilization of nutrients. I investigated the effect of genotypic richness and genotypic dissimilarity on N uptake by . Genotypic richness is defined by the number of strains in the bacterial community. Genotypic dissimilarity is calculated as the average genetic distance between the strains in the bacterial communities. Genotypic dissimilarity hereby refers to functional dissimilarity, as phylogenetic and functional distances are linked.
My results show that diversity of root-associated microbial communities is central for nutrient mineralization and plant performance. For detection of positive or negative effects of diversity on functional processes, genotypic richness as well as genotypic dissimilarity has to be considered. Publication of my results is in progress.
The experiment was set up in the facilities of the working group Bonkowski at the University of Cologne, while subsequent analyses were done in the working group Scheu at the University of Göttingen.