Project Area B

Understanding the Mechanisms that Generate Community Structures

This project area will investigate the underlying regulative mechanisms that lead to a change in metabolic signatures within complex communities and the associated function of such changes. We will examine regulation on a genetic, biochemical, as well as on a metabolic level and underscore the dynamic modulation of the metabolism in specific interactive or stress situations.

Focus of project area B is the elucidation of regu­lative principles controlling the release and per­ception of metabolites active at a community level.

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Chemical imaging techniques
(also in conjunction with Z2) will help monitor the chemical landscape in communities thereby answering central questions about the formation of signaling hot spots or chemospheres around single organisms or consortia.

This approach will allow all partners to overcome the shortcomings of established bioassays that often rely on the determination of average concentrations of metabolites in, e.g., cultures, and the application of solutions of these metabolites. The effect of abiotic factors such as metal composition or light on the metabolic interplay of different interaction partners in soil, biofilms or plankton will be another focus. Additionally, several projects will be linked through the examination of another core topic regarding the regulation of specific enzymatic switches and the activation of silent gene clusters in the presence of a complex multi-organism community.

Project B01

Cryptic Mediators at the Bacterial-Fungal Interface

This project explores interactions of bacteria and fungi with the aim to identify factors that either promote or moderate infection processes. We investigate the role of mushroom 'helper bacteria' and protective symbionts of beneficial soil fungi that inactivate virulence factors and shield the host from predators, respectively. Beyond gaining insight into ecologically relevant multi-partner interactions, our findings have translational value for agriculture and medicine.

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Project B02

Bacteria-triggered Activation of Fungal Silent Gene Clusters and Impact of Produced Compounds on Microorganisms

We discovered a tripartite microbial interaction between the bacterium Streptomyces iranensis, the fungus Aspergillus nidulans and the green algae Chlamydomonas reinhardtii. This interaction is determined by the bacterial azalomycin F. It induces the activation of the silent orsellinic acid gene cluster in A. nidulans and the fungus protects C. reinhardtii from killing by azalomycin F. Project B02 aims at the elucidation of (i) the targeted release of azalomycin F towards A. nidulans and C. reinhardtii, (ii) the mechanism underlying the activation of fungal ors genes by azalomycin F and (iii) the identification of chemical mediators triggering azalomycin F release and attracting C. reinhardtii to A. nidulans.

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Project B03

Chemical Factors Structuring Gut Microbial Communities of Insects

We will explore the chemical factors controlling the composition of microbial communities in the gut of the African Cotton Leafworm Spodoptera littoralis. In particular, the formation of iron chelators, such as 8-hydroxyquinoline-2-carboxylic acid by the insect’s gut tissue could be used to control the composition of the consortia. Fluorescent Enterococci, integrated in the microbiome, will be used for transcriptome analyses along the gut and over all developmental stages of the insect. The approach is expected to provide an overview on adaptation strategies of the microorganisms in the changing environments during the development of the insect.

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Project B04

Stimuli-Responsive Microcapsules for Transport, Controlled Delivery and Release of Metal Ions and Organic

Conventional bioassays apply chemical mediators in average concentrations in solution. This is by no means in a close to natural situation where local concentration maxima around producing organisms appear. The project aims for the design of loaded polymeric microcapsules which are responsive to pH changes and illumination. They will act as point-sources for chemical mediators with spatial resolution and will mimic chemically active microbes that shape their immediate environment through the release of metabolites. The capsules will be applied and evaluated in several collaborations within the CRC.

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Project B05

Role of Basidiomycete Small Molecules on Habitat-sharing Microbes


The interaction between wood-rotting basidiomycetes like Serpula lacrymans and Schizophyllum commune with each other and with the co-occurring bacteria like Bacillus subtilis determines overall degradation rates, while natural products mediate the community interactions. With the tripartite interactions, we plan to study how bacteria impact growth of basidiomycetes that grow in consortia (organismic level), and how stimuli by consortia are transduced inside the basidiomycete cell (cellular level) to aid future applications in wood protection by providing signals for the targeted manipulation of the community.

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Project B06

Photoresponsive Modulation of a Freshwater Phytoplankton Community by Bacterial Lipopeptides

To analyze the role of siderophores in selected bacteria-microalgae encounters a tripartite work program has been designed. In the first work package siderophore-mediated growth effects on microalgae will be evaluated in supplementation studies with a model compound and, subsequently, in co-culturing experiments with producer organisms. The second package aims at identifying exogenous signals that modulate siderophore biosynthesis. In the third subproject, we will test the generalizability of mutualistic iron sharing in planktic consortia via a genomics-guided approach.

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Project B07

Plant Defence Detoxification Strategies of Aboveground and Belowground Herbivores in a Multitrophic Context


Herbivores that feed readily on chemically defended plants may have evolved detoxification strategies, including the use of microbial (gut) symbionts. We aim to identify the major detoxification routes for two types of insect herbivores, aboveground phloem feeders and root-feeding herbivores, feeding readily on Brassicaceae chemically defended with glucosinolates. Using multiple techniques ranging from (meta) genomics to behavioral assays, we will elucidate detoxification mechanisms and assess their effects on herbivore performance and on higher trophic level organisms associated with the herbivore.

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Project B08

Fundamentals and Applications of Chemical Mediators Facilitating Multilateral Interactions in Cyanobacteria


Facultative symbiotic cyanobacteria of the genus Nostoc are prolific producers of a plethora of bioactive compounds and show versatile chemical interactions with plant hosts and other microorganisms. This project aims to understand the role of specialized metabolites for the specificity of the interactions of Nostoc with growth-promoting heterotrophic bacteria. The findings will be applied to further develop cyanobacteria as chassis for the production of specialized compounds and to increase robustness and productivity in synthetic biology applications.

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Project B09

Enzymatic Modification of Chemical Mediators


Many complex microbial traits are only established within multi-species interactions. We found that Paenibacillus and Pseudomonas strains cooperate against amoebal predators. This defense strategy relies on the Pseudomonas strain secreting a lipopeptide, which itself is innocuous to the predator. This compound, however, is peptidolytically modified by the Paenibacillus strain, yielding a lipopeptide, which is highly toxic to the amoebae. We will investigate the structural basis of lipopeptide processing and the influence of the amoebicidal lipopeptide on membranes. This will allow the discovery of novel bioactivity compounds and generate new tools for the structure elucidation of complex nonribosomal peptides.

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