Transformation of Lactobacillus helveticus subsp. jugurti with plasmid pLHR by electroporation.

Lactobacillus helveticus subsp. jugurti was transformed with plasmid, pLHR (8.5 kilobases), by electroporation. The plasmid, pLHR, consists of a cryptic plasmid, pLJ1, from L. helveticus subsp. jugurti, the Escherichia coli vector pBR329, and the erythromycin resistance gene of pAM beta 1 from Enterococcus faecalis. Maximum transformation efficiency of 1.3 x 10(4) transformants per microgram of DNA was obtained by exposure to a pulse with an exponential decay waveform at 4 kV/cm with 25 microF capacitance. The presence of glycine in the growth medium was essential for transformation. Plasmid DNA isolated from transformants had not undergone detectable rearrangements or deletions. In addition, it was found that L. helveticus subsp. jugurti has a restriction and modification system.