Purification of pili from Escherichia coli and Salmonella typhimurium. A preliminary report.

A new procedure was developed for the purification of pili from Escherichia coli and Salmonella typhimurium. The pili were removed from the bacterial cells by mechanical agitation and then concentrated by precipitation with ammonium sulfate. After dialysis, the pili were solubilized in a buffer containing deoxycholate. This treatment did not solubilize the outer membrane proteins. The pili were then separated by ultracentrifugation in a sucrose gradient and finally passed through a Sepharose 4B column in a 6 M urea buffer. The pili were not dissociated by concentrated urea and they eluted in the void volume of the Sepharose 4B column. Because the enterobacterial flagella dissociate in concentrated urea, this procedure enables the purification of the pili from the flagellated strains also. The purified pilus proteins were free from lipopolysaccharide and outer membrane proteins. The molecular characteristics and the binding properties of these pilus proteins are briefly described.