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The optimum conditions and mechanisms for the plasmid-mediated genetic transformation of intact cells of Bacillus brevis P176-2, an extracellular protein producing bacterium, by electroporation were investigated. It was found that pUB110 plasmid DNA can be introduced into intact bacterial cells by electroporation. The frequency of transformation by this electroporation system depended upon the initial electric field strength, the capacity of the electric discharge capacitor, growth stage, number of successive pulses and composition of electroporation buffer. It was effective for transformation that cells were harvested, washed and resuspended with HSM [7mM HEPES(pH 7.4), 272mM sucrose, 1mM MgCl_2] electroporation buffer when cell growth was attained to 1.2 at OD_660. A maximum frequency of transformation of 2.40×10 exp (4) transformants per ㎍ plasmid DNA was obtained by two succesive pulses with an initial electric field strength of 12.5㎸/㎝ and with a capacitance of 7.3㎌.
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