The different cleavage patterns of pYBamy59 plasmid isolated from E. coli DH5alpha and B. longum MG1 by the cell extract of B. longum MG1 suggested that the main reason for low transformation efficiency was related to the restriction modification (R-M) system. To confirm correlation between R-M system and transformation efficiency, in vitro methylation and site directed mutagenesis was performe...
