Purification of sex pili from Escherichia coli carrying a derepressed F-like R factor.

A procedure for the purification of sex pili is described. Escherichia coli K-12 carrying Rldrd19 was grown in nutrient broth and blended at the time of peak sex pilus production. The cells were removed by centrifugation, and the supernatant fraction was concentrated, dialyzed, and clarified in an ultrafiltration system. After an additional blend and a clearing spin, the material was centrifuged in a CsCl gradient, and the fractions containing the sex pili were subjected to isoelectric focusing. About 5 mg of intact pili of approximately 98% purity were obtained by this method from about 100 g (wet weight) of cells.