Practice question

Minimal medium contains only essential inorganic salts, nitrogen source, carbon source such as glucose, and trace elements, without amino acids, vitamins, or nucleotides. Only organisms possessing intact biosynthetic apparatus for all growth factors can proliferate, meaning prototrophs. Auxotrophs lacking even one pathway fail to grow unless specific supplement restores requirement. Selection for prototrophic recombinants after conjugation or transformation uses minimal medium to eliminate auxotrophic parents. Therefore minimal medium distinguishes metabolic competence and allows direct scoring of wild-type alleles complementing mutations.