Illuminating the relationship between flagellar activity and bacterial swimming
Bacterial swimming and chemotaxis serves as a model system for understanding information processing in living organisms. My thesis project was focused on studying the swimming behavior of Escherchia coli bacterial cells. These cells swim by rotating helical filaments called flagella. An individual cell can have anywhere from 1 to 10 flagella. In a process called chemotaxis, cells modulate the rotational direction of their flagella to modify their swimming behavior and move towards more favorable environments. The primary goal of this thesis was to determine how the number of flagella on a cell affects its swimming behavior. I designed and constructed a unique instrument, combining optical tweezers and high-speed fluorescence imaging. This instrument allowed me to simultaneously measure the activity of the individual flagella on a cell, while also monitoring the swimming behavior of the cell. These results provided a large amount of data regarding the relationship between flagella number, CW bias and tumble bias. In particular, I discovered that the tumble bias of a swimming cell is robust against variations in flagellar number. Cells with 2 flagella and cells with as many as 8 flagella have the same average tumble bias. Many other results regarding this system are presented throughout this thesis. The goals and organization of the thesis are summarized in Chapter 1.
Escherichia coli, biophysics, optical tweezers, chemotaxis, fluoresence imaging, systems biology
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign