REGULATION OF R100 CONJUGATION REQUIRES TRAM IN CIS TO TRAJ

Deletion mutants of R100-1 were constructed by classical methods to re move various segments of the fraM open reading frame, pTraM-binding si tes and the fraM promoters. Complementation tests showed that traM was efficiently complemented only when the transacting fragment contained both the complete traM gene and the adjacent traJ promoter and leader sequences. The conclusion is that fraM and traJ constitute a complex operon. A deletion mutant lacking all of the traJ gene, and one contai ning a frameshifting fraM deletion, retained the ability to transfer a t a low level, thereby showing that neither pTraM nor pTraJ is absolut ely essential for transfer.