Difference between Pili and Fimbriae

Pili and fimbriae are cell surface appendages present in bacteria other than flagella. These structures are not for locomotion.

Pili and fimbriae are surface appendages for attachment.

 Pili vs Fimbriae

Pili	Fimbriae
Long, thicker, tubular structures made up of protein pilin	Thin and shorter than the pili
Pili are found only in Gram negative bacteria	Fimbriae are found both in Gram negative and Gram positive bacteria
The number of pili are less (3-5 per cell)	The number of fimbriae is 300-400 per cell
Formation of pili is governed by plasmid genes	Formation of fimbriae is governed by bacterial genes in the nucleoid region
Pili, involved in cell to cell attachment during bacterial conjugation. Therefore called as sex-pili	Fimbriae is involved in cell to surface attachment of bacteria