Optimization and Comparison of Two Electrotansformation Methods for Lactobacilli

To date, lactobacilli are widely used in food industries and new probiotic products; hence these are considered as an attractive target for genetic modifications. This study was conducted to improve electroporation of probiotic lactobacilli which is a necessary prerequisite for genetic manipulations. Four strains of probiotic lactobacilli from different sources were grown in Man Rogosa and Sharp (MRS) broth medium containing glycine, as a cell wall weakening agent or a pulse of glycine for evaluation of glycine effect on electroporation efficiency. After evaluation of various parameters such as washing buffers, washing times, electric field strength, pulse duration and plasmid concentration, a practical electroporation protocol was presented to improve electrotransformation of lactobacilli in comparison with two standard protocols. This new protocol exhibited higher transformation efficiency (transformants/g plasmids) than standard methods (p<0.05) with no differences between species (Lb. casei, Lb. crispatus, Lb. salivarus and L. rhamnosus). The pulse of glycine had no effect on the number of the transformants in three methods. In contrast to plasmid concentration, plasmid size had no influence on the transformation efficiency. The modified method enabled to transform plasmid into the resistant lactobacilli against transformation. These bacteria have potential for bioengineering research to improve special performance.