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. We will also incorporate the development of functional polymer-based stimuli responsive delivery systems. With these tools, we will deliver natural products that are identified as candidates for the mediation of complex interactions. It should be emphasized that this approach will allow for a local delivery of compounds (e.g. from micrometer-sized beads as point sources or from surfaces). In this way, we will mimic the release of metabolites from individual microbes or biofilms.

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: Mushroom Soft Rot Diseases as Infection Model

We will explore bacteria-induced mushroom diseases as a general model for infection processes and the impact of the microbial communities on the host colonization. We aim at monitoring the chemical mediators involved in the infection process and their regulation by imaging mass spectrometry and genome mining. At a higher level of complexity, we will investigate the modulation of bacterial pathogenicity in natural and artificial biosystems. Beyond providing insights into the molecular basis of mushroom diseases we expect to learn general principles of multipartner interactions in infection processes in a much broader context.

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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

This project focuses on the consequences for basidiomycete secondary metabolism when confronted with microbial consortia of increasing complexity. The response of basidiomycetes regarding induction of natural product pathways will be investigated, both with analytical and molecular biology methods.

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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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