Lactobacillus transformation (Kim 2005)

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Electrotransformation procedure for Lactobacillus acidophilus, Lactobacillus brevis, and Lactobacillus helveticus.


Prepare Electrocompetent cells

  1. Use overnight culture (106 CFU/mL) to inoculate 100mL MRS containing 1% glycine.
  2. Grow until OD660 = 0.2-0.3.
  3. Place culture into two 50mL centrifuge tubes and chill on ice for 10 mins.
  4. Wash 2X with cold washing buffer (5 mM NaH2PO4, 1mM MgCl2, pH 7.4):
    1. Centrifuge for 5min at 4000g.
    2. Resuspend in unspecified amount of washing-buffer.
    3. Repeat.
  5. Concentrate in electroporation-buffer (1mM sucrose, 3mM MgCl2, pH 7.4):
    1. Centrifuge for 5min at 4000g
    2. Resuspend in unsepcified amount of electroportion buffer.
  6. Keep on ice and transform cells within 30 minutes.


  1. Add 1μL (25 ng/μL) of plasmid DNA to 50 ul (108 CFU/ml) of ice-cold cell suspension.
  2. Electroporate at 12.5 kV/cm (pulse number = 10, puse interval = 500 ms).
  3. Dilute electroporated cells to 1ml in MRS broth and incubate at 37°CC for 3 hours.
  4. Plate bacteria onto MRS agar plates with appropriate antibiotic.
  5. Incubate under anaerobic conditions.


  • Used plasmid pNZ123, works with L. acidophilus strains 43121, 4356, NCFM, 30SC, A4, 107A, GP4A; L. helveticus KU107; L. brevis 3102 *Derek Ju 04:44, 29 October 2008 (EDT):
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  • Kim, Y.H., Han, K.S., Oh, s., You, S. and S.H. Kim (2005) "Optimization of technical conditions for the transformation of Lactobacillus acidophilus strains by electroporation." Journal of Applied Microbiology 99: 167–174


  • Derek Ju (derekju [at]

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