The dynamical extracellular matrix of bacterial colonies

细菌4型菌毛（T4P）是一种动态的细胞外聚合物，对附着宿主细胞、运动、生物膜形成和水平基因转移至关重要。以前，我们和其他人已经证明，它们的动力学和结合特性控制着淋病奈瑟菌（一种广泛传播的人类病原体）形成的菌落的物理特性。然而，人们对它们在生物膜成熟过程中的作用以及它们如何与细胞外基质（ECM）的其他成分相互作用知之甚少。在这里，我们将通过使用共聚焦成像，定量图像分析，激光镊子和分子生物学的组合来解决这一知识差距。我们将测试淋球菌ECM的机械特性是由使菌落流化的动态T4P和稳定菌落的静态细胞外DNA （eDNA）纤维之间的相互作用调节的假设。首先，我们将独立表征单个T4P的动态和三维淋球菌菌落内eDNA网络的形成。随后，我们将重点关注它们在单细胞水平上的相互作用，并将结果与结构、机械性能和菌落的稳定性联系起来。另一个主要目标是找出外部压力如何影响ECM的形成，反之亦然，基质如何保护细菌免受外部压力的影响。从长远来看，我们的目标是了解ECM是如何重塑的。我们计划生成具有设计特性的DNA凝胶，并研究这些特性如何影响菌落生长和合成基质的重塑。生物膜的物理特性对生物膜适应环境变化、增殖和抗逆性具有重要意义。因此，了解ECM如何调整这些特性是至关重要的。

Bacterial type 4 pili (T4P) are dynamical extracellular polymers that are essential for attachment host cells, motility, biofilm formation, and horizontal gene transfer. Previously, we and others have shown that their dynamics and binding properties govern the physical properties of colonies formed by Neisseria gonorrhoeae, a wide-spread human pathogen. However, little is known about their role during the maturation of biofilms and how they interact with other components of the extracellular matrix (ECM). Here, we will address this gap of knowledge by using a combination of confocal imaging, quantitative image analysis, laser tweezers, and molecular biology. We will test the hypothesis that the mechanical properties of the gonococcal ECM are adjusted by the interplay between dynamic T4P that fluidize the colony and static extracellular DNA (eDNA) fibres that stabilize the colony. First, we will independently characterize the dynamics of individual T4P and the formation of the eDNA network within three-dimensional gonococcal colonies. Subsequently, we will focus on their interaction at the single cell level and link the results to structure, mechanical properties, and stability of colonies. Another major aim will be to find out how external stresses affect ECM formation and, vice versa, how the matrix protects bacteria from external stresses. In the longer term, we aim at understanding how the ECM is remodeled. We plan on generating DNA gels with designed properties and investigate how these properties affect colony growth and remodelling of the synthetic matrix. The physical properties of biofilms are important for adaptation to changing environment, proliferation, and stress tolerance. Thus, it is crucial to understand how the ECM adjusts these properties.