ELECTROTRANSFECTION OF PROPIONIBACTERIUM-FREUDENREICHII TL-110

The first highly efficient protocol is described for the electrotransf ection of Propionibacterium freudenreichii with DNA phage. The transfe ction efficiency is 7 x 10(5) transfectants per mu g of DNA under opti mal conditions. Optimized parameters included the field strength (12.5 kV, 200 Ohms, 25 mu F), phage DNA concentration (1 mu g ml(-1)) and c ell density (1.5 x 10(10) cells ml(-1)). Growth in the presence of gly cine and harvesting of cells during the early exponential growth phase increased the transfection efficiency. This electrotransfection proto col is of importance for the genetic improvement of dairy propionibact eria.