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

This project focuses on the role of secondary metabolites as mediators of the complex plankton community structure. It will elucidate the interaction of lytic bacteria with susceptible and resistant microalgae. In this project the signals controlling lytic activity of the bacteria as well as the nature and mechanism of the observed induced defense in the diatom Chaetocerous didymus are addressed. Using these signals or active fractions complex co-cultures as well as natural plankton communities in mesocosms will be manipulated to understand the role of chemical signals and lytic events the open waters of the oceans.

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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?

All plants contain metabolites that prevent the attack of unadapted herbivores, and thwart the growth of adapted herbivores. To cope, herbivores sequester, metabolize, or excrete the defensive metabolites consumed in their food. We propose that this processing of plant defensive metabolites by herbivores produces a vast and largely unexplored infochemical network that sculpts most higher trophic interactions. Uncovering this infochemical network is the goal of this proposal, and it is a goal that we can attain, because we finally have the tools to do so in a rigorous experimental manner in the real world.

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Project C03

Thiopeptide Signals in Actinomycete Communities

Thiopeptides (TPs) are complex secondary metabolites that target specific receptors in actinomycetes. In this project, selective TPs and TP derivatives will be accessed by using semisynthesis and fermentation. Signals triggered by them through the tipA regulatory pathway will be tracked by bioinformatics, transcriptome and proteome analysis as well as chemical probing techniques. The investigation of TP-mediated communication in co-cultures and soil microcosms under normal and stressed conditions will illuminate the interconnection and significance of these regulatory factors.

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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

Chemistry will provide the tools in a project rooted in microbiology to elucidate the identity and characteristics of metallophores involved in microbial iron cycling. We hypothesize that competing effects between iron chelators secreted in a multi-organism microbial community and exogenous organic ligands affect rates of microbial iron oxidation and reduction. We will use a broad set of approaches including metallophore typing, a library of synthetic chelating agents, voltammetric techniques, metatranscriptomics and proteomics to study biological processes in manipulated consortia

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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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