Ecology of Bacterial Communities: Interactions and Pattern Formation

细菌群落是复杂的动态生态系统。它们以自由漂浮的细菌和生物膜的形式出现在我们环境的几乎所有地方，与人类健康和疾病高度相关。空间格局的形成是由潜在“景观”的异质性或细菌间相互作用的自组织性决定的，在维持物种多样性方面起着重要作用。相互作用包括资源竞争和通过共享胞外聚合物进行合作等。另一个相互作用的方面是化学战。一些细菌菌株产生毒素，如大肠杆菌素，它作为一种毒药敏感菌株，而其他菌株是耐药的。当这些不同的菌株可以在空间上分离时，它们就会稳定共存，从而产生自组织模式。在我们的研究项目中，我们想采用大肠杆菌Col E2系统，包括一个产毒，敏感，和抗性菌株，定量研究新兴模式的形成。通过实验和理论方法的结合，我们的目标是表征和定量的单细胞相互作用，以及在个人的流动性，外部异质性和随机效应对所产生的模式的影响。实验将采用微生物学技术，例如荧光细菌菌株的克隆、荧光显微镜检查和图像分析。我们的理论研究将基于非线性动力学和随机过程理论的分析方法，以及数值模拟。

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.