Thin, hairlike appendages, 1 to 20 microns in
length and often occurring in
big numbers, gift on the
cells of
gram-negative bacteria, particularly enterobacteriaceae and neisseria. Unlike flagella, they do not possess motility,
but being protein (pilin) in character, they possess
antigenic and haemagglutinating properties. They are of
medical meaning because some
fimbriae mediate the
attachment of
bacteria to
cells via adhesins (adhesins, bacterial). Bacterial
fimbriae refer to
general pili, to be distinguished from the preferred
use of "pili", which is confined to
sex pili (pili, sex).