Subtopic 3.1: Bacterial Reverse Mutation Assay (Ames Assay )
This assay was discovered by Bruce Ames in 1970. This assay is widely used to test for gene mutation. The technique uses several strains of the bacterium Salmonella typhimurium which carry mutations in genes involved in histidine synthesis. These strains are auxotrophic mutants and they require histidine for growth and they cannot produce it. This assay examine the ability of the chemical or mutagen in creating mutations or a "prototrophic" state of strains, when the strains can grow on a histidine-free medium (Figure 1).