Electrotransformation of intact cells of Brevibacterium flavum MJ-233

Electroporation allowed transformation of intact cells of Brevibacterium flavum MJ-233. The two plasmids used for electroporation were pCRY2 (6.3 kilobase) and pCRY3 (8.2 kilobases). Both plasmids contain the chloramphenicol-resistance gene and the autonomous replication origin in B. flavum MJ-233. The efficiency of electrotransformation was optimal with cells harvested at the middle log phase of growth, and was improved by the addition of 1.0 U/ml of penicillin G to the culture medium. The optimum yield of transformants per micrograms DNA was 5 x 10(4) when the cell suspension was pulsed at a cell density of 1 x 10(10)/ml and at a DNA amount of 1.0 micrograms.