Fimbria

A fimbria (plural fimbriae) is an appendage in many gram-negative bacteria that is thinner 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 for attaching to surfaces and for movement. A bacterium can have as many as 1,000 fimbriae. Fimbriae are only visible with the use of an electron microscope.