New method for electroporation of Lactobacillus species grown in high salt

We here describe a new method for electroporation of Lactobacillus species, obligately homofermentative and facultatively heteroferrnentative, based on the cell-wall weakening resulting from growth in high-salt media. For L casei, optimum transformation efficiency of up to 10(5) transformants per microgram of plasmid DNA was achieved following growth in the presence of 0.9 M NaCl. Plasmids of different sizes and replication origins were also similarly transformed. These competent cells could be used either directly or stored frozen, up to 1 month, for future use, with similar efficiency. This protocol was assayed with different Lactobacillus species: L delbrueckii subsp. lactis, L paracasei, L plantarum and L acidophilus, and it was found that they were transformed with similar efficiency. (C) 2010 Elsevier B.V. All rights reserved.