M9 Minimal Salts solution contains buffering agents, a nitrogen source, ions such as phosphorus and sulfur, and metal ions. It is generally supplemented with glucose, amino acids, and vitamins for preparation of M9 minimal medium, which is used for non-selective cultivation of E. coli strains for cloning, production of DNA plasmids, and production of recombinant proteins. Upon addition of appropriate antibiotics, M9 minimal media can also be used for selective cultivation of E. coli strains