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Short Video: Prokaryotic Flagella

by Pearson
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This is a dark-field video of bacterial cells of the species Salmonella typhimurium filmed with a full-intensity beam. Due to light scattering, the cells appear to be larger than their actual size, and you can see the flagellum on each cell clearly. Many bacteria swim by rotating their flagella in a helical manner. In media of normal viscosity, the flagella are moving too fast for their helical waveform to be seen. Toward the end of this clip, the cells are placed in a highly viscous medium. The flagellar rotation is now slow enough for you to see the waveform easily. Flagellar motion occurs by means of a set of proteins that act together as a motor, fueled by a proton gradient across the plasma membrane. Changing the direction the flagella are rotating causes the cells to move in a different direction. Credit: Robert Macnab, Professor of Molecular Biophysics and Biochemistry at Yale University.
This is a dark-field video of bacterial cells of the species Salmonella typhimurium filmed with a full-intensity beam. Due to light scattering, the cells appear to be larger than their actual size, and you can see the flagellum on each cell clearly. Many bacteria swim by rotating their flagella in a helical manner. In media of normal viscosity, the flagella are moving too fast for their helical waveform to be seen. Toward the end of this clip, the cells are placed in a highly viscous medium. The flagellar rotation is now slow enough for you to see the waveform easily. Flagellar motion occurs by means of a set of proteins that act together as a motor, fueled by a proton gradient across the plasma membrane. Changing the direction the flagella are rotating causes the cells to move in a different direction. Credit: Robert Macnab, Professor of Molecular Biophysics and Biochemistry at Yale University.