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LB Medium and Agar Plate Recipe (also L-Broth or Luria Bertani)

Composition:
1.0% Tryptone
0.5% Yeast Extract
1.0% Sodium Chloride (NaCl)
pH 7.0

Protocol for LB liquid medium:

  1. For 1 liter, dissolve 10 g Tryptone, 5 g yeast extract, and 10 g NaCl in 950 ml deionized water.
  2. Adjust the pH of the solution to 7.0 with NaOH and bring the volume up to 1 liter.
    It may not be necessary to adjust pH every time, since pH of LB naturally close to pH 7.0. This might be affected by your yeast extract.
  3. Autoclave on liquid cycle for 20 minutes at 15 psi. Allow solution to cool to 55 C and add antibiotic if needed.
  4. Store at room temperature or at 4°C if antibiotic is added.

Protocol for LB agar plates:

  1. Prepare LB medium as above, but add 15 g/L agar before autoclaving.
  2. Autoclave on liquid cycle for 20 minutes at 15 psi.
  3. After autoclaving, cool to ~55 C, add antibiotic, and pour into 10 cm plates.
  4. Let harden, then invert and store at +4 C, in the dark.

Good luck with your cloning and other experiments!