Isolation of IS elements from rhizobium strains; Characterisation of rhizobium and bradyrhizobium strains using isolated IS elements

摘要

The broad host range plasmidp SUP 104 carrying theudstreptomycin sensitivity gene - S12, was m obilized fromudEscherichiaco1i S17-1 to Rhizobium meliloti 2 011, R.l er.uminosarum 897 and two Brad vrhizobium.iaponicum serogroup 123 strains. Transconjugants were purified from the two Rhizobium strains. The plasmid pSUP104-S12 failed to replicate in the B..Iaponicum serogroup 123 strains and no transconjugants were isolated. The plasmid pSUP104-S12 induced a streptomycin sensitive phenotype in R.me 1 i 1 oti 2011 and IU1 inosarum which were previously streptomycin resistant. The selection for streptomycinudresistant revertants carrying the pSUP104-S12 plasmid causedudinsertion of IS elements directly into the S12 gene. Two ISudelements were isolated, one ISRm2 is a 1.25 Kb IS elementudisolated from R.me 1 i loti 2011, the other ISR11 is a 2.7 Kb IS element isolated fron R.leguminosarum 897.ududBoth IS elements caused deletions of the pSUP104-S12 plasmidudin a Rec A- E.coli strain.ududHybridization analysis using 32P labelled pSUP104-S12::ISRm2udas a probe with EcoRl digests of total chromosomal DNA ofudvarious Rhizobium and B..iaponicum serogroup 123 strainsudrevealed that ISRm2 was particular to R.me1 i 1oti strains. By the same method ISR11 was found in all the Rhizobium strains tested and in most of the B..iaponicum serogroup 123 strains. It would be possible to use ISR 1 1 as a pr o b e in DNA fingerprinting to identify a B,.iaponicum serogroup 123 inoculum from an indigenous B..iaponicum serogroup 123 in field trials of a serogroup 123 inoculum.udBoth IS elements were implicated in DNA rearrangements inudRhizobium strains.