Fimbriae (also called pili), polar filaments radiating from the surface of the bacterium to a length of 0.5-1.5 micrometers and numbering 100-300 per cell, enable bacteria to colonize the epithelium of specific host organs. Seems to anchor the pilus to the bacterial cell. In addition the stoichiometric relationship between PrsH and PrsA determines the pilus length. Belongs to the fimbrial protein family.