| dc.description.abstract | Vibrio alginolyticus is a marine bacterium with dual flagellar motor systems, single polar flagellum and lateral flagella. Polar flagella expression is encoded in each division cycle and the lateral flagella expression is environmental induced. While the cells growing on agar plate, they elongate without division into swarming phase and express high density lateral flagella. Swarming cells shows environmental sensing and different responses to swimming cells. However, there is no experimental assay suitable for well controlled swarm cell experiments due to the special two dimensional semi-solid agar surface environments. In this thesis, we develop a technique to manipulate swarm cells by drawing “channel” on the agar plate with a glass micro-pipette manipulator system. We demonstrate three manipulation methods on agar plates. 1. Guide cells in different type of channels. 2. Create local constrains to trap cells. 3. Local chemical treatments on cells. Combining these powerful methods, one can design desired experiments based on this “Lab on the agar plates” assay.
In biophysical research, bacterial chemotaxis represents a powerful model system to understand how single-cell organisms sense and respond to external chemical gradients. Most of the chemotaxis researches focus on the cells swimming in aqueous environment. However, very little is known regarding the swarm cell chemotaxis. Traditional chemotaxis capillary assay and modern microfuidic assay are very difficult to apply to the swarm cell chemotaxis in situ. In this thesis, we use “Lab on the agar plates” assay to perform chemotaxis experiments on the swarm cells in situ. Swarming cells developed on the swarm colony can be guided to specific locations to experience particular attractant or repellent with designed gradient for high resolution single cell observation. Vibrio alginolyticus swarm cells with only lateral flagellar shows two interesting chemotaxis response to the repellent phenol. First, there concentration response shows two binding concentration. Second, the cells shows different speed of moving toward and away from the phenol. These two new finding shed new directions of understanding the swarm cells chemotaxis.
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