Amestest

The Ames test is a biological assay used to assess the mutagenic potential of chemical compounds by measuring reverse mutations in bacteria. It was developed in the 1970s by Bruce N. Ames and colleagues as a simple, rapid screen for genetic toxicity that could be used for hazard identification and screening in pharmaceuticals, environmental testing, and industry.

The test uses strains of the bacterium Salmonella typhimurium that carry specific mutations in their histidine operon, which render them unable to synthesize histidine. When exposed to a mutagen that causes a back-mutation restoring histidine biosynthesis, the bacteria regain the ability to grow on histidine-free medium, forming colonies known as revertants. The number of revertant colonies is compared to controls to evaluate mutagenicity.

Mutagenicity testing is typically performed with and without metabolic activation. An S9 liver extract, usually from rodents, is added in the metabolic activation setup to simulate mammalian metabolism, allowing certain pro-mutagens to be converted into active mutagens.

Common Salmonella strains used include TA98 and TA100, which detect frameshift mutations and base-pair substitutions, respectively. Other strains such as TA1535, TA1537, and TA102 may be employed to broaden the mutational spectrum. The assay can be conducted as a plate incorporation test or a pre-incubation version, depending on the protocol.

Ames test results are widely used for initial hazard screening. A positive result indicates mutagenic potential and may prompt further testing, while a negative result does not guarantee safety. Results are typically interpreted alongside additional genetic and toxicological data to assess potential human risk.