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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 bacteria-induced mushroom diseases as a general model for infection processes, and the impact of the microbial communities on the host colonization. We investigate the modulation of bacterial pathogenicity in complex microbial assemblages and elucidate the context-dependent functions of the chemical mediators involved. Beyond gaining insight into the molecular basis of mushroom diseases we expect to learn general principles of multi-partner interactions in infection processes from a broader perspective.

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Project B02

Mechanisms of 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. S. iranensis induces the activation of the silent orsellinic acid gene cluster in A. nidulans and the fungus protects C. reinhardtii from killing by S. iranensis. Project B02 aims at the elucidation of (i) the bacterial signals triggering the fungal response, (ii) the mechanism by which the transcription factor BasR in combination with chromatin modifications transmits the bacterial signal and (iii) how the fungus protects C. reinhardtii from killing by S. iranensis.

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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 genetic basis of natural product gene regulation in basidiomycetes is poorly understood, in particular when responding to bacterial cues. This project aims at identification of natural product gene transcription factors in the model fungus Serpula lacrymans, primarily focusing on the key biosynthesis genes for pulvinic acids. As these biofilm and motility-inhibiting compounds are synthesized by numerous basidiomycetes, our work addresses a fundamental principle of how they interact with bacteria that surround them.

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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

Chemical Mediators Facilitating Multilateral Interactions Between Nitrogen-Fixing Cyanobacteria and the Liverwort B. pusilla

 

Terrestrial filamentous cyanobacteria with capability for nitrogen fixation are widespread as facultative symbionts in different plant hosts. Symbiotic interactions are strongly influenced by chemical mediators, structures of which are largely unknown. The project aims to understand the impact of intraspecific chemical interactions for structuring the community of cyanobacteria in soil and their symbiotic interactions with the host plan B. pusilla and aims to elucidate underlying mechanisms.

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