MINIMAL AGAR

Nutritional mutants of Escherichia coli obtained by the exposure of wild type E. coli to ultra violet light need a nutritionally complete medium to grow. Minimal media can be supplemented with the desired additives to study nutritional characters of the nutritional mutants. Minimal media are the formulations of Davis as described by Lederberg. Minimal media contain the necessary nutrients only for the growth of wild type E. coli strains. By the random isolation method described by Lederberg, nutritional mutants derived from irradiated cultures of wild type E. coli can be isolated. These mutants can also be isolated by the use of penicillin as described by Davis and Lederberg. Bacillus subtilis mutants can be isolated by these techniques and by the penicillin technique also, as described by Nester et al.
A cell suspension of wild type E. coli is irradiated and cultured on Minimal Agar supplement with all the necessary growth requirements. This will allow growth of both wild type cells (prototrophs) and mutant cells. The selected colonies are then added to Minimal Broth, Davis and Minimal Broth Davis supplemented with the growth requirements and incubated at 35?C for 24 hours. Growth in the Minimal Broth supplemented with growth requirements and no growth in Minimal Broth indicates a mutant for that particular factor.

for isolation and characterization of nutritional mutants of Escherichia coli