An efficient method for the transformation of Lactobacillus acidophilus TK8912 by electroporation is presented. The plasmid vector pULA105E was constructed by joining a cryptic plasmid, pLA 105, from L. acidophilus TK8912, the Escherichia coli vector pUC19, and the erythromycin resistance gene of the Streptococcus-Escherichia coli shuttle vector pVA838. Plasmid pULA105E was introduced into L. acidophilus TK1-5 at a frequency of 7.4 × 106 transformants per μg of plasmid DNA under optimized conditions. Other Lactobacillus strains, L. casei JCM 1053 and TK9008, were also transformed with pULA105E.
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