Filamentous Protein Appendages

Many bacteria have protein appendages that are anchored in the membrane and protrude out from the surface. These structures are not essential to the life of the cell, but they do allow some bacteria to exist in certain environments in which they otherwise might not survive.

Flagella

The flagellum is a long protein structure responsible for most types of bacterial motility (figure 3.38). By spinning like a propeller, using proton motive force as energy, the flagellum pushes the bacterium through liquid much as a ship is driven through water. Flagella must work very hard to move a cell, since water

Chapter 3 Microscopy and Cell Structure

Chapter 3 Microscopy and Cell Structure

Figure 3.38 Flagella (a) Peritrichous flagella (SEM); (b) polar flagellum (SEM).

has the same relative viscosity to bacteria as molasses has to humans. Nevertheless, their speed is quite phenomenal; flagella can rotate more than 100,000 revolutions per minute (rpm), propelling the cell at a rate of 20 body lengths per second. This is the equivalent of 6-foot man running 82 miles per hour!

In some cases, flagella are important in the ability of an organism to cause disease. For example, Helicobacter pylori, the bacterium that causes gastric ulcers, has powerful multiple flagella at one end of its spiral-shaped cell. These flagella allow H. pylori to penetrate the viscous mucous gel that coats the stomach epithelium. ■ Helicobacter pylori, p. 605

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Responses

  • ulla-maj
    What is the causative agent of filamentous?
    1 year ago

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