(also called fimbriae) are short, fine, rigid protein appendages of the cell wall that help the bacterium adhere to the tissue of its host.
pl Pili Very thin filaments (ca. 10 nm diameter) filaments on the surface of some bacteria. They appear to be hollow tubes used to transfer genes.
elongated, proteinaceous, plasmid-encoded structures extending from the surface of Gram-negative bacteria that express conjugative plasmid; some types have been shown to be essential in conjugation.