Genetic transformation of Rhizobium meliloti by plasmid DNA

A procedure for the genetic transformation of Rhizobium meliloti by plasmid DNA is described. It is an adaptation of a procedure used originally for Escherichia coli and later for Agrobacterium tumefaciens. Depending on the R. meliloti isolate used as the recipient, the efficiency of transformation was in the range of 7 x 10(1) to 3.7 x 10(3) per microgram of plasmid pRK248 DNA and 10(-6) to 10(-9) per viable cell. A number of different naturally occurring strains could be transformed. Plasmids related to pRK248 and varying in size from 9.6 to 56 kb could be used, suggesting that the procedure will be useful for molecular cloning of genes in R. meliloti.