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Microbiology: An Evolving Science 4th Edition

Microbiology: An Evolving Science (4th Edition)

Book Edition4th Edition
PublisherW. W. Norton
End of Chapter
Review Questions

Chapter 25, End of Chapter, Review Questions, Exercise 7

Page 1034

Here is a tip:

The difference in protein sequences give rise to type I and type IV pili that helps in adhesion.


Pili have tips that can bind with the host cell membrane. The shafts of pili consist of pilin proteins and are cylindrical structures. The tip protein initiates the assembly of pilus that binds to the carbohydrate present on the host cell surface. The attachment of tip allows the assembly of other pilin subunits to form the shaft. The shaft forces the tip protein to move farther.

The pili are of two different types that are type I and type IV pili.

Type I piliType IV pili
  • Type I pili are static and wait to bind their receptors.
  • Type I possess special proteins that can bind to substrates.
  • The type IV pili are dynamic and responsible for the twitching motility.
  • Type IV pili is mainly responsible for the pathogenicity of the bacteria.
Example: Escherichia coliExample: Vibrio cholerae

Verified Answer

The pili assembly starts with the tip protein which binds with the carbohydrate of the host cell membrane. The remaining subunits of pilus join together and force the tip protein in forward direction to adhere to the cell surface of the host.

Type I pili is stable as compared to the type IV pili which is more dynamic. 

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