Tn1000 insertional mutagenesis of cloned repressor gene of the phage L: plasmid oligomerization in the presence of F'lac.

An ampicillin resistance plasmid carrying the cloned repressor gene cII of the L phage (Salmonella typhimurium) was conducted by F'lac into an F- recipient. Two types of plasmids were isolated from Apr transconjugants. The majority of plasmids were dimers with one copy of Tn1000 inserted, the minority being monomers with one copy of Tn1000. This proportion remained unaltered when we used the F'lac strain transformed with a monomeric form of the recombinant plasmid as a donor. An extensive oligomerization of pBR322-originating plasmids was proved in the presence of F'lac; its presumable relationship to transposition-related processes is suggested.