Abstract
Pili are widespread among bacteria. Type IVa pili (T4aP) are associated with a variety of bacterial functions, including adhesion, motility, natural transformation, biofilm formation, and force-dependent signaling. In pathogenic bacteria, T4aP play a crucial role during infection and have been the subject of hundreds of studies. Methods for the isolation and purification of T4aP were first described in the 1970s. Purified pili have been used for studies of filament protein content, morphology, immunogenicity, post-translational modifications, and X-ray crystallography. We detail a tried-and-true method of isolating large amounts of native T4aP from bacterial surfaces. The method requires supplies and equipment that are available in most microbiology labs.