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Maintenance and evolution of cooperation in synthetic microbial ecosystems

This new project explores cooperative interactions in synthetic microbial ecosystems and their effect on population heterogeneity. For this purpose, we focus on a bacterial model system, the production of the iron-scavenging pyoverdine by Pseudomonas. We consider ecological metapopulations containing producers (cooperators) and non-producers (free-riders) of pyoverdine (public good) and ask how phenotypic heterogeneity, ecological factors, environmental conditions and the properties of the underlying gene regulatory network affect the dynamics of the microbial population. In particular, we are interested in the interplay between stochastic effects (intrinsic, demographic, and extrinsic noise), interaction between the microbes (selection), and population structure.

We combine experimental studies with mathematical models, which are quantitatively validated uponcomparing with experimental results. Using fluorescence time-lapse microscopy we plan to quantitatively analyse expression of genes involved in pyoverdine biosynthesis and its regulation at the single cell level over time using respective reporter gene fusions. By this means, we plan to obtain information on the impact of varying social and environmental conditions on stochastic processes underlying pyoverdine production. To investigate the influence of ecological factors on population heterogenity, we reconstitute near-natural but experimentally well-controlled conditions.

In a broader context, we are aiming at understanding the emergence and maintenance of “social” behavior in bacterial populations where phenotypic heterogeneity is subject to selection mechanisms associated with competition between different strains and due to population structure.

Cooperation with Prof. Dr. Erwin Frey, Theoretical Physics, LMU Munich

Financing: DFG