AB medium

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  • AB medium is a minimal growth medium used for bacterial cultures. It has some changes compared to M9 medium and is supposed to cause less problems with precipitation [1].


for 1 liter AB medium
2 g (NH4)2SO4
6 g Na2HPO4
3 g KH2PO4
3 g NaCl
200 ml H2O

Prepare and autoclave.

for 1 liter AB medium
1 ml 0.1 M CaCl2 (sterile)
1 ml 1.0 M MgCl2 (sterile)
1 ml 0.003 M FeCl3 (sterile)
797 ml H2O (sterile)

Mix 200ml 5xA and 800ml B to get 1 liter AB. Do never add B salts to 5xA!

If you want agar-plates add 16g agar to 1xB, autoclave and than add 5xA.

Different things can or should be added:

  1. Carbon source (has to be added):
    1. 0.2% glucose (10ml of 20% or 4ml of 50% sterile stock)
    2. 0.4% acetate (20ml of 20% sterile sodium-acetate stock)
  2. Amino acids (check AA requirement of your strain):
    1. 0.5% casamino acids (50ml of 10% sterile stock)
    2. For CM735 add 20 μg/ml methionine (10 ml of 2mg/ml stock), 20 μg/ml tryptophane (5 ml of 4mg/ml stock) and 25 μg/ml histidine (1 ml of 25 mg/ml stock);
  3. 10μg/ml thiamine (1 ml of sterile 10 mg/ml stock)
  4. 25μg/ml uridine (2.5 ml of sterile 10 mg/ml stock)(uridine makes E. coli K12 wildtypes as MG1655 of W3110 grow better because they are starving from pyrimidine [2].)


  1. Clark, DJ and Maaløe, O DNA replication and the division cycle in Escherichia coli Journal of Molecular Biology

    Volume 23, Issue 1, 14 January 1967, Pages 99-112 abstract

  2. Jensen KF. The Escherichia coli K-12 "wild types" W3110 and MG1655 have an rph frameshift mutation that leads to pyrimidine starvation due to low pyrE expression levels. J Bacteriol. 1993 Jun;175(11):3401-7. DOI:10.1128/jb.175.11.3401-3407.1993 | PubMed ID:8501045 | HubMed [Jensen-JB-1993]


  • Please feel free to edit this page, add comments on the talk page or contact the page beginner Torsten Waldminghaus.