ChemBioSys - Chemical Mediators in Complex Biosystems

Discovery of Chemical Mediators and their Targets

Partners in this area had the task to discover chemical mediators that function specifically in a community context. 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 were poorly understood until we started with ChemBioSys. Project area A led to the discovery and elucidation of several metabolites and their corresponding genes that act specifically in communities.

Understanding the Mechanisms that Generate Community Structures

This project area addressed the underlying regulative mechanisms that lead to a change in metabolic signatures within complex communities and the associated function of such changes. We revealed principles of regulation on a genetic, biochemical, as well as on a metabolic level and underscored the dynamic modulation of the metabolism in specific interactive or stress situations.

Chemical imaging techniques helped to monitor the chemical landscape in communities thereby answering central questions about the formation of signaling hot spots or chemospheres around single organisms or consortia.

This approach allowed 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 was another focus.

Additionally, several projects were linked through the common 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.

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.

For the in-depth understanding of complex systems, natural products or other chemical compounds with a documented or highly likely potential as mediators of interaction were used as starting points. Furthermore, the modulating role of metal ions or their depletion due to complexation with natural products was explored.

Non-contact co-culturing allowed the effects of direct cell-cell interactions to be separated from the true function of secreted metabolites. This approach was 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 directly facilitated the observation of the response of (natural) communities to chemical signals. Synthesis of multimodal peptides provided a link between metabolic diversity and functional diversity of natural products within stressed and non-stressed bacterial communities.

Metallophores were also explored as mediators for metal cycling to understand how communities can be shaped by metal chelating reagents.