Team:SDU-Denmark/Protocols/Competent-cells

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Protocol for making cells (E. coli) competent

(Cells are kept on ice at all times!! If the temperature rises above ~5˚C they lose their competency)

  1. 2ml over-night cell culture is transferred to 200ml Luria Bertani (LB)-medium.
  2. Incubate at 37˚C on shaker until OD550=0.5-0.7
  3. Keep on ice for 15-30min and harvest by 4000 x g for 15 min at 4˚C.
  4. Remove all supernatant and resuspend carefully in 200ml ice cold dH2O. Harvest as in 3.
  5. Resuspend in 100ml ice cold dH2O. Harvest as in 3.
  6. Resuspend in 20ml ice cold 10% glycerol. Harvest as in 3.
  7. Resuspend in ice cold 10% glycerol until a total volume of 1ml. Cell concentration should be 1-3x1010 cells/ml.
  8. Cells are distributed in tubes with 40ul in each and kept at -80˚C.