No abstract

The Escherichia coli-Brevibacterium Zactofermentum shuttle vector pBLA was introduced into intact cells of B. lactofermenturn by electrotransformation. Several parameters of this procedure such as voltage and cell concentration were analysed. Optimal conditions gave an efficiency of lo6 transformants per pg of DNA. Two recalcitrant strains could be electrotransformed when an ampicillin pretreatment step was used. Electrotransformation experiments using DNAase or different structural forms of plasmid DNA showed that the electrotransformation process is quite different from natural transformation involving competence development. Restriction-modification-proficient B. lactofermentum could be efficiently electrotransformed with pBLA DNA isolated from E. coli. This restriction-modification system therefore seems to be overcome by electrotransformation. Thus electrotransformation may efficiently replace the protoplast bacterial transformation method.