LB Amp is Lysogeny Broth (LB) containing the antibiotic ampicillin. Because LB is a rich medium for growing bacteria, adding ampicillin provides a means of selecting transformants that have taken up plasmid DNA containing the bla gene, which encodes resistance to ampicillin. Consequently, only bacteria that have been successfully transformed with such a plasmid will survive in LB Amp.


Dissolve the following in 1L ddH2O:

  • 10g bacto-tryptone
  • 5g bacto-yeast extract
  • 10g NaCl (5g in some recipes)

Adjust to pH 7.0 with 1N NaOH

Autoclave at 121°C for 20 minutes

Allow solution to cool to RT

Add 1000μL 100mg/mL ampicillin

[Amp]final = 100μg/mL

Store at 4°C or RT