Practice question

Complete medium is enriched with yeast extract, peptone, casein hydrolysate, vitamins, and all amino acids, providing preformed metabolites that bypass biosynthetic needs. Minimal medium lacks these additives, forcing cells to synthesize their own. Adding supplements to minimal converts it to supplemented or complete medium that supports both prototrophs and auxotrophs. Classic Luria-Bertani, nutrient agar, or YPD are examples of complete media. The contrast allows replica plating screens where colonies grown on complete medium are tested for failure on minimal, identifying auxotrophic mutations.