Project Area A

Discovery of Chemical Mediators and their Targets

Partners in this area have the task to discover chemical mediators that function specifically in a community context. Obviously, single species of unicellular organisms such as bacteria and microalgae communicate by using quorum-sensing type chemicals as well as pheromones. We also know that allelochemicals released in the presence of, e.g. a co-cultivation partner can enable the producer to perform better. However, mediators that affect the entire consortia and that are released in consortium-specific situations are poorly understood, especially at a chemical level. Project area A now aims to discover and elucidate metabolites and their corresponding genes that act specifically in communities.

Project area A aims to elucidate the chemical mediators affecting multipartner interactions.
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Project A01

Identification of novel infochemicals and their biopathways mediating the cross kingdom
communication between Ulva (Chlorophyta) and associated bacteria: An approach using genetic transformation of macroalga.

The project aims to understand the cross-kingdom interactions between the marine green algae Ulva mutabilis and the associated bacteria. The bacteria release morphogens such as Thallusin. They induce various algal developmental processes. Developmental mutants of Ulva, which show the characteristics of callus-like axenic cultures, even in the presence of bacteria, will be used to reveal the signal transduction of morphogens. Hereby, the project also focuses on the mechanism of DNA modification which might control epigenetic processes.

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Project A02

Identification of Novel Secondary Metabolites with Roles in Interactions Between Chlamydomonas reinhardtii and Other Microorganisms

Albeit microalgae are key contributors to global carbon fixation, their interactions with other microbes in terrestrial, freshwater and marine ecosystems are barely known. We have investigated the interplay of the green alga Chlamydomonas reinhardtii with other microorganisms and found that Pseudomonas protegens strongly inhibits algal growth. The bacteria immobilize the algae by secreting cyclic lipopeptides that cause Ca2+ signals and deflagellation. We now aim to understand the molecular mechanism of this signal cascade along with the involved proteins and will screen for further chemical mediators and partners in this interplay.

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Project A03

Characterization of Novel Biomolecules Establishing Mutualistic Interactions with Roots of Arabidopsis and Nicotiana Species


The root-colonizing fungi Piriformospora indica (Pi) und Mortierella hyalina (Mh) promote the fitness of plants. We study perception and early Ca2+-dependent signaling steps in Arabidopsis roots which are induced by the chemical mediators cellotriose from Pi, short-chain cello-oligomers, and a furan from Mh, which inform the plants about changes in their cell walls and the rhizosphere. Furthermore, the role of a S-containing volatile released by Mh and of a N2-fixing bacterium in Mh will be studied in the tripartite plant-fungus-bacterium interaction.

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Project A04

Chemical Mediators in the Interaction Between Phagocytes and Their Prey


Macrophages and amoebae are both exquisite systems to study the combat between phagocytes and bacteria or aberrant mammalian cells. Small molecule mediators play crucial, yet poorly understood roles in the interaction between these phagocytes and their prey. We will shed light on two related but contextually distinct aspects of chemical signaling during phagocytosis of different preys by studying a) lipid mediators as signals in the communication between human macrophage phenotypes and cancer cells, and b) toxin production as bacterial defense mechanism against the phagocyte Dictyostelium discoideum.

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Project A06

Isolation, Characterization and Functional Analysis of Novel Biomolecules from the Mutualistic Food Fungus and Associated Microbes of Fungus-Growing Termites


This project will explore which chemical mediators are secreted by the fungal cultivar Termitomyces to (a) orchestrate the symbiotic relation with fungus-growing termites, (b) protect the fungus garden against competitors and alien species, and (c) how the fungus responds to natural organismic and abiotic stress factors. This CRC project will provide fundamental insights into the remarkable success of fungiculture and clarify the molecular contributions and mechanisms to maintain symbiotic interactions.

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