TRANSPOSITION INHIBITION OF Tn5 IN Rhizobium leguminosarum

A recombinant transposon Tn5-GmSp,produced by replacing the central BglⅡfragmentwith a BamHⅠone of R1033,was utilized to detect Tn5 transposition inhibition in Rhizo-bium leguminosarum.Two types of suicide plasmids(pXS102 and pCW3/pCW30)were con-structed for Tn5-GmSp transposition.The frequency of transposition in both constructs wasgreatly reduced in the Rhizobium strains where a resident Tn5 was already present.WhenpXS102 was transferred into a Tn5-containing Rhizobium strain,the transconjugants retainedthe deleted forms of pXS102,indicating that the failure of transposition was due to the lossof the unstable prophage Mu element.In the case of pCW3/pCW30,vectors were not ob-served in the transconjugants although most of them retained the antibiotic resistant markers.This result suggested the integration of Tn5-GmSp into the rhizobial host genome through recombination.