Index >> Bacterial Structure >> Fimbriae / Pili

Fimbriae / Pili - Many gram negative bacteria have hair-like appendages called fimbriae or pili given off from their surface.

These appendages seem to be restricted to the gram negative bacteria (Enterobacteriaceae, Pseudomonadaceae and Caulobacter).

In the gram positive bacteria similar, structures have been observed only in Corynebacterium renale.

Fimbriae and pili of bacteria differ from flagella in being, thinner, straighter and less rigid.

They are also usually much more numerous than flagella

.Their length varies from 0.2-20 μ m and their width from 30A to 40A.

Some have a diameter of 250A. In Agrobacterium the peritrichous fimbriae are 1-3 μm long and 400A-600A wide.