Project Area C

Directed Modulation of Complex Biosystems

Whereas the projects in areas A and B explore new community relevant metabolites and regulatory principles, this project area will take these concepts and specifically examine complex communities by using natural products and derivatives as modulators. Multi-organism communities with varying degrees of complexity will be manipulated using natural products or their synthetic analogues and their response will be characterized on different levels. This includes field ecology, work in mesocosms or targeted manipulations of communities in environmental samples.

Focus of project area C will be the effect of mediators on communities.

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Natural products or other chemical compounds with a documented or highly likely potential as mediators of interaction will be used as starting points. Furthermore, the modulating role of metal ions or their depletion due to complexation with natural products will be explored. Non-contact co-culturing allows the effects of direct cell-cell interactions to be separated from the true function of secreted metabolites. This method will be used to study how complex plankton communities respond to chemical signals produced by introducing additional partners.

Field experiments that allow the observation of microbes and plants in their natural environment will directly facilitate the observation of the response of (natural) communities to chemical signals. Synthesis of multimodal peptides will provide a link between metabolic diversity and functional diversity of natural products within stressed and non-stressed bacterial communities. Metallophores will be investigated as mediators for metal cycling to understand how communities can be shaped by metal chelating reagents.

Project C01

Algicidal Bacteria in Plankton Communities: Resistance, Lysis and Heterotrophy


Organisms in the plankton form complex communities that contribute substantially to global primary production and fuel the marine food web. This project focuses on the role of secondary metabolites as mediators of the complex plankton community structure. We focus on the lytic bacterium Kordia algicida that is capable of lysing bloom forming algae and investigate its influence on plankton dynamics. Control of lytic activity, release of organic resources due to cell lysis and response of the resistant and susceptible members of the algal community is in the focus of lab and field experiments.

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Project C02

Are Plant Defenses Chemicals Commonly Sequestered and Metabolized by their Herbivores to Function as Infochemicals in Higher Trophic Level Interactions in Nature?


Plants integrate responses between two spatially separated habitats: air and soil, with different communities of heterotrophs depending on the same host. Little is known about the chemical mediators of interactions between aboveground herbivores and root colonizers. Using metabo-lomics and transcriptomics, we will characterize spatiotemporal changes in roots of herbivore-damaged plants and identify underlying signalling pathways. We will genetically modify identified traits to determine their ecological function in interactions with soil bacteria and mycorrhizal fungi and the consequences for herbivore resistance and plant fitness in field experiments.

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Project C03

Thiopeptide Signals in Actinomycete Communities


Microbial consortia are structured by antibiotics such as thiopeptides (TP) and by environmental factors such as heavy metals (HM). In this project the signaling of sublethal TP doses via the TP-activated TipA receptor and its interaction with HM-stress and resistance mechanisms will be investigated on the molecular, genomic and interspecies level. Ligand function, target genes, and HM-dependence will be clarified in model organisms and microcosms by using targeted mutants, tool compounds, and HM-contaminated soil media.

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Project C04

Metallophores as Mediators for Metal Cycling: Profiling and Ecological Evaluation of Ligands Involved in the Microbial Cycling of Iron in Complex Systems


We aim to obtain in depth insights into interspecies cell-cell chemical communication of microbes involved in different parts of the Fe-cycle. We hypothesize that interactions between Fe-oxidizing, Fe-reducing, and Fe-assimilating bacteria have evolved specifically such that these bacteria thrive in habitats rich in iron and organic matter. We could show that metallophores, but also other chemical compounds, were excreted and utilized by at least one of the partners. Thus, we have to elucidate in more detail the molecular mechanisms underpinning the interactions of the three model bacteria using comparative transcriptomic analyses and targeted metabolomics studies.

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Project C05

Metallophores as Mediators for Metal Cycling: Development of Libraries for Metal Ion Buffering and as Redox Carriers as well as Profiling of Metallophores

This project aims to identify novel metallophores based on recently developed LC/MS analytical techniques and to unravel their multiple functions particularly in nitrogen-fixing and microbial iron-cycling systems. To mimic natural sources of molybdenum, which is an essential cofactor of nitrogenases, we will develop libraries of synthetic chelating agents for this metal. The resulting complexes serve as “Mo-buffers” to control the availability of molybdenum species in aqueous cultures. To model redox shuttle systems in communities of Fe(II) oxidizers and Fe(III) reducers appropriate ligands as well as metal complexes will be developed.

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Project C07

Computer Simulation and Game-Theoretical Analysis of Microbial Consortia


In microbial communities, often a superposition of mutualism and competition can be observed. Theoretical analysis and computer simulation are instrumental in understanding the resulting complex phenomena. The present project is aimed at elucidating complex interactions in microbial communities by mathematical modelling and simulation, with a special focus on tripartite communities. Three methodologies will be used: ordinary differential equation systems, evolutionary game theory and individual- based modelling. The project will serve as an essential part in the iterative cycle experiment-theory-experiment.

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