In
bacteriology, a
fimbria [(plural
fimbriae); also referred to as "attachment pili" by some scientists] is an appendage composed of curlin
proteins that can be found on many
Gram-negative and some
Gram-positive bacteria that is thinner and shorter than a
flagellum. This appendage ranges from 3-10 nanometers in diameter and can be up to several micrometers long. Fimbriae are used by bacteria to adhere to one another and to adhere to animal cells and some inanimate objects. A bacterium can have as many as 1,000 fimbriae. Fimbriae are only visible with the use of an
electron microscope. They may be straight or flexible.