IMPROVEMENT IN ELECTROPORATION EFFICIENCY FOR LACTOBACILLUS-PLANTARUMBY THE INCLUSION OF HIGH-CONCENTRATIONS OF GLYCINE IN THE GROWTH-MEDIUM

The electroporation efficiency of Lactobacillus plantarum NCFB1193 usi ng plasmids pLP3537 or pLP825 was improved by the inclusion of glycine in the growth medium. Optimum transformation efficiency was achieved following growth for 4.5 h in the presence of 6-8% (w/v) glycine prior to electroporation. An additional improvement was obtained when the m edium also contained 0.3 M sucrose and the results became more reprodu cible. Consistent frequencies of > 10(4) transformants per mu g plasmi d DNA could be obtained using an electroporation voltage of 7.5 kV cm( -1). The use of multiple pulses, increasing cell densities and increas ing the concentration of magnesium ions in the electroporation buffer did not affect the transformation efficiency significantly. A number o f previously non-transformable strains of Lb. plantarum were rendered electrocompetent by the modifications to the growth medium described.