Ecology of Bacterial Communities: Interactions and Pattern Formation

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Bacterial communities represent complex and dynamic ecological systems. They appear in the form of free-floating bacteria as well as biofilms in nearly all parts of our environment, and are highly relevant for human health and disease. Spatial patterns arise from heterogeneities of the underlying “landscape" or self-organized by the bacterial interactions, and play an important role in maintaining species diversity. Interactions comprise, amongst others, competition for resources and cooperation by sharing of extracellular polymeric substances. Another aspect of interactions is chemical warfare. Some bacterial strains produce toxins such as colicin, which acts as a poison to sensitive strains, while other strains are resistant. Stable coexistence of these different strains arises when they can spatially segregate, resulting in self-organizing patterns. In our research project, we want to employ the Escherichia coli Col E2 system, comprising a poison producing, a sensitive, and a resistant strain, to quantitatively study the emerging pattern formation. By a combination of experimental and theoretical methods, we aim at a characterization and quantification of the single cell interactions, as well as the in influence of individuals' mobility, external heterogeneities and stochastic effects on the resulting patterns. Experiments will employ microbiological techniques such as cloning of fluorescent bacterial strains, fluorescence microscopy, and image analysis. Our theoretical studies will be based on analytical methods from nonlinear dynamics and the theory of stochastic processes, as well as numerical simulations.