A new method for transformation of Bacillus megaterium was developed by modification of Chang and Cohen's method. In our method, spore spheroplasts were used as recipent cells instead of the protoplasts of vegetative cells. Longer incubation (60min) of spore spheroplasts and plasmid DNA before treatment with polyethylene glycol remarkably increased the efficiency of transformation. The frequency of transformation was about 104 per μg of plasmid DNA. A shot-gun-type cloning of chromosome DNA of B. megaterium ATCC 12872 was available in B. megaterium ATCC 19213 strain by this transformation method.
