CONSTRUCTION OF DERIVATIVES OF THE F-PLASMID POX-TRA715 - CHARACTERIZATION OF TRAY AND TRAD MUTANTS THAT CAN BE COMPLEMENTED IN TRANS

A derivative of the F plasmid, pOX38-tra715, expresses the entire F tr a operon from a foreign promoter (P-T7) derived from phage T7, A serie s of plasmids related to pOX38-tra715 were constructed which carry eit her deletion mutations or point mutations in traY. When the P-T7 promo ter was induced, these plasmids expressed the F pilus but were transfe r deficient unless TraY was supplied in trans from compatible plasmids . Insertion of a kanamycin-resistance cassette in the traY gene of the pOX38 plasmid, which contains the wild-type P-Y promoter, resulted in loss of F piliation and transfer ability. Introduction of TraY in tra ns partially restored piliation and transfer suggesting that TraY has a role in positively regulating the P-Y promoter. pOX38-fra719-traD411 , which contains a chloramphenicol-resistance cassette in place of the kanamycin-resistance cassette in pOX38-tra715 and a mutation in traD, was constructed to demonstrate the utility of this series of plasmids in studying the long (30 kb) F tra operon.