Behaviour of bacteriophage Mu-based IncP suicide vector plasmids in Rhizobium spp.

Abstract The ability of P-type plasmids, containing bacteriophage Mu, to survive in Rhizobia was examined under conditions in which the plasmids were not directly selected. The plasmid pRP4::Mu::Tn7 survived in all tested strains of Rhizobia and Agrobacteria . The surviving plasmids were analysed for expression of plasmid coded properties and for presence of both bacteriophage Mu and Tn7 DNA. A large variation in plasmid size and coding capacity was observed. In the parent plasmid Tn7 is inserted into the Mu DNA. The majority of surviving plasmids had lost Mu DNA but the Tn7 DNA was retained. Analysis of surviving plasmids which contained Mu DNA indicated that a small deletion of Mu is sufficient to allow plasmid survival. Deleted derivatives of pJB4J1 were also isolated in Rhizobium under similar conditions. The potential of these suicide vectors as potential vectors for transposon mutagenesis in Rhizobium is discussed.