Efficient transformation of Mesorhizobium huakuii subsp rengei and Rhizobium species

The transformation of Mesorhizobium huakuii subsp. rengei B3 with either pB BR122 or pKT230 was carried out. We determined the optimal conditions requi red for transformation by electroporation and obtained up to 10(5) CFU/mu g pBBR122. Plasmids prepared from strain B3 yielded higher transformation ef ficiency than those from various dam or dcm mutant strains of Escherichia c oli. This result suggests that a high transformation efficiency is not rela ted to the methylation of plasmid DNA in E. coli. Using the optimal conditi ons for electroporation, we performed transformation of several species of Rhizobium, Mesorhizobium and Sinorhizobium. All tested strains of these spe cies were transformed with pBBR122. Strains of M. huakuii and R. phaseoli A HU1133 were transformed at high efficiency, whereas transformation efficien cies of Rhizobium sp. NGR234 and S. meliloti strains were less than 2 x 10( 3) CFU/mu g plasmid DNA.