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 main objectives of the project are to elucidate the signal-mediated cross-kingdom interactions between the marine green macroalgae Ulva mutabilis and its associated bacteria. Axenic cultures develop into callus-like colonies of undifferentiated cells. A combination of two isolated strains, Roseobacter sp. and Cytophaga sp., are required to restore the algal morphogenesis forming a tripartite community. Chemical analysis will be used to identify involved signals and genetic approaches will shed light on their bacterial biosynthesis and perception by Ulva

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Project A02

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

Relatively little is known about the interactions of eukaryotic soil-dwelling and freshwater microalgae with other microorganisms at the chemical level. Here, we will exploit the molecular tools and genome sequence available for the unicellular green alga Chlamydomonas to systematically investigate its interactions with other microorganisms, including the nature and roles of secondary metabolites, biosynthetic genes and signaling components induced by the algal-microbial interactions. Our studies will deepen our understanding of algal communication and secondary metabolites in freshwater and soil ecosystems.

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Project A03

Isolation and Characterization of Novel Biomolecules from Fungi Establishing Mutualistic or Pathogenic Interactions with Roots of Arabidopsis and Nicotiana Species

Beneficial and pathogenic fungi release biomolecules into the rhizosphere, which induce cytoplasmic calcium elevation in roots of higher plants. We will use the calcium sensor aequorin to identify exudated active biomolecules from fungi. Metabolome, proteome, transcriptome and phosphoproteome profiling will be performed to study early signaling events in roots triggered by these compounds. Map-based cloning and sequencing will lead to the identification of Arabidopsis genes involved in cytoplasmic calcium elevation. The role of these mediators in the complex environment of the plants will be evaluated in field experiments.

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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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