Transformation of Lactobacillus casei by electroporation

Electroporation has been used to introduce DNA into both eucaryotic and procaryotic cells. Since current methods for the transfection and transformation of lactobacilli using protoplasts are slow, inefficient, and inconsistent, we evaluated electroporation as a simple alternative. In initial experiments, PL-1 phage DNA (40 kb) was transfected into untreated cells of Lactobacillus casei by electroporation. Approximately 50% of the CFU survived pulses of 5000 V/cm at 25 μF; conditions found to be optimal for the transfection process. The β-galactosidase-encoding plasmid, pLZ15 (28 kb), and the vectors pSA3 (Emr), pLP825 (Cmr) and pNZ12 (Cmr) transformed L. casei at efficiencies of 1.1–8.5 × 104 transformants/μg DNA. Plasmid DNA isolated from pNZ12 containing transformants was used to retransform L. casei and was indistinguishable from authentic preparations of pNZ12 by gel electrophoretic analysis.