LB

Summary

Luria-Bertani Medium (aka L-Broth or LB Medium). (Bertani says LB really stands for lysogeny broth.) LB is a standard growth medium for a variety of bacteria and conditions.

Ingredients

1. 10 g Bacto-tryptone
2. 5 g yeast extract
3. 10 g NaCl

For plates also add

1. 15g agar

See also: Silver: LB Liquid

Note: There are two formulations of LB, Miller and Lennox, that differ in the amount of NaCl. Lennox has less salt, only 5 g/L. The Qiagen miniprep kit recommends LB with 10 g NaCl for highest plasmid yields.

Protocol

1. Mix dry ingredients and add distilled water up to 1 Liter
2. Pour into 2 L flask (or greater)
3. Autoclave (liquid cycle)
   • 250°F, 22psi, 30 minutes

Notes: We do not pH medium when we make it on the fly. However, if it is really important, pH the medium to 7.0 with 5M NaOH (~200µL). Check with pH paper

For plates

1. Mix dry ingredients and add distilled water up to less than 1 Liter
2. After dissolved, add agar
3. Pour into 2 L flask (or greater)
4. Autoclave (liquid cycle)
   • 250°F, 22psi, 30 minutes
5. Cool media down to 60-55C (uncomfortable but not painful)
6. Add appropriate antibiotic
7. Pour the solution on sterile (???) plates
8. Let solidify about 1 h, wrap, label (name, date, additive)
9. keep at 4°C

Source

Adapted From:

J. Sambrook, D.W. Russell, Molecular Cloning: A Laboratory Manual (Cold Spring Harbor Laboratory Press, New York, ed. 3, 2001) pg. A2.2