Bacteria swim by rotating thin helical filaments known as flagella. For bacteria, such as Escherichia coli and Salmonella typhimurium, flagella are typically 10 µm in length, but only 20 nm in diameter. It is because of this small diameter that visualizing individual flagellum in real time can be very difficult. In this video, using high resolution fluorescence imaging, we display some of the rich dynamics that occur when bacterial flagella are subjected to various applied shear flows. It is shown that flagella can both rotate and undergo geometrical changes in their helical shape under these types of flows. Understanding these flagellar dynamics can give us insight into microbial transport, which has broad implications ranging from infection, disease, and reproduction, to the design of future biologically inspired nanorobots.
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