The dynamical extracellular matrix of bacterial colonies

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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.