Specific Piliation Directed by a Fertility Factor and a Resistance Factor of Escherichia coli

Abstract

SUMMARY: Production of pili directed either by the sex factor F or by the drug-resistance factor R 100 in Escherichia coli K12 is regulated by a gene which acts by producing a represser, and the mutant R100–1 no longer produces this repressor. The specific pilus determined by R100–1 resembled the F pilus morphologically, but differed in its affinity for F-specific RNA phages. Mutants of F and R100-I which had lost the ability to synthesize pili could each restore to the other the ability to produce pili on mixed infection of the same host.