M9 Minimal Salts (5×) BD Difco™ 500 g. Used in preparing M9 Minimal Medium which is used for cultivating recombinant strains of Escherichia coli. M9 Minimal Salts, 5× is a 5× concentrate that is diluted to a 1×concentration and supplemented with an appropriate carbon and energy source, such as dextrose, to provide a minimal, chemically defined medium. The medium will support the growth of “wild-type” strains of E. coli. M9 Minimal Salts is useful for maintaining positive selection pressure on plasmids coding for the ability to produce essential substances such as amino acids or vitamins. M9 Minimal Medium is also used to maintain stocks of F’-containing bacteria for use with M13. The medium can be supplemented with specific amino acids or other metabolites, allowing for selection of specific auxotrophs.