Index >> Bacterial Recombination >> Properties Of Sexual Mating Types

The donor E. coli cells have F pili or sex fimbriae - on their surface, in addition to the type I pilus. Phages like R17 and M12 are adsorbed on the F pili, but not on recipient bacteria. The adsorption of the RNA phages is at random sites along the length of the sex pilus. Male-specific DNA phages bind to the tip of the pilus. The number of F pili on donor cells is much less than the number of type I pili. Often only one F pilus is present per cell, and there are never more than three pili. Under certain conditions of growth there may be up to five pili per cell. There is a correspondence between the number of F pili and the number of copies of the F factor. This had led to the conclusion that each pilus is synthesized under the direction of one F factor