M9 Plates -Leu

Contributed by Ian Chin-Sang, Queens University, ON, Canada

The following recipe is for one litre of plates.

The salts need to be autoclaved separately from the agar, for this reason prepare the following two mixtures in flasks (make sure one is a 2 litre flask since you are going to combine the mixes after autoclaving):


  • Mix 1: Salt mix in 500ml of water:
  • 6g Na2HP04
  • 3g KH2P04
  • 0.5g NH4Cl
  • Mix 2: Agar:
  • 15g Agar
  • 500ml Water
  • Autoclave mixes 1 and 2—after autoclaving combine the two mixes and add the following sterile solutions to the mixture:
  • 1ml 1M MgSO4
  • 0.1ml 1MCaCl2
  • 4.0ml 50% Glucose (filter sterilized)
  • 0.69g -Leu Drop Out
  • Pour plates and label appropriately. 1L = ~40 plates

This method is based, with permission, on an original protocol available here.