M9 Minimal Medium Salts (5X)

Principle and Interpretation

M9 Minimal Salts, 5x is used in preparing M9 Minimal medium used for the cultivation and maintenance of E. coli in molecular biology. M9 is a chemically defined minimal growth medium for E. coli cultures (1, 2). It can be supplemented with specific amino acids or other required nutrients for the selection of some specific auxotroph. Sometimes the incorporation of certain additives (e.g. thiamine or casamino acids) enhances the bacterial growth. In 1959, Jacob and Monod published an article where they discussed about minimal media of E. coli (3). The components of this media supply the required nutrients for proper growth. Ammonium chloride acts as the nitrogen source and Sodium chloride maintains the final osmolarity of the medium. M9 Minimal Salts Base, 5x, is a 5x concentrate and should be diluted to 1x concentration before usage. Glucose may be added as a carbon source. Some other nutritional elements (e.g. calcium and magnesium) can be added as supplement.