Dr. Kun Zhao
University of California Los Angeles
In this talk I show how mesoscopic physics can impact fields as diverse as colloid science and microbiology. In directed self-assembly of colloidal systems, particle shape can greatly drive structure formation. As an example, we show rich phase behavior of a dense Brownian system of anisotropic triangular colloids. Using enhanced optical video particle-tracking microscopy, we show that microscale triangles form two different triatic liquid crystal phases. The same classes of colloid physics techniques can lead to transformational progress in bacterial biofilms, which are self-organized communities of bacteria on surfaces that can cause major problems in human health, such as lethal infections in cystic fibrosis. Despite sustained effort, much of biofilm development is still poorly understood. The first social step in organizing a structured biofilm is the formation of microcolonies, which are assemblies of 50-100 cells. By translating video microscopy movies into searchable databases of bacterial trajectories by adapting algorithms from colloid physics, we show why bacteria form microcolonies for the first time, using Pseudomonas aeruginosa as a model system. We will also show preliminary data that reveal the impact of cdiGMP signaling on this process, which is a biological feature that is not found in typical physical systems.