Ames Assay

Ames test, developed by Bruce Ames, is a widely used rapid and less-expensive screening test for potential mutagens.


Figure 1. The Ames test for mutagenicity. The test uses a strain of Salmonella bacteria that require histidine in the medium because of a defect in a gene necessary for histidine synthesis. Mutagens can cause a further change in this gene that reverses the defect, creating revertant bacteria that do not require histidine. To increase the sensitivity of the test, the bacteria also have a defect in their DNA repair machinery that makes them especially susceptible to agents that damage DNA. A key feature of this detection system is the inclusion of a mammalian liver homogenate as some potential carcinogens are converted into their active forms by enzyme systems in the liver or other mammalian tissues and bacteria lack these enzymes, and so the test plate requires a few milligrams of a liver homogenate to activate this group of mutagens. (Figure and text from Molecular biology of the Cell, IV Ed.)


Additional Information:

>Bruce N. Ames, E. G. Gurney, James A. Miller, and H. Bartsch (1973). "Carcinogens as Frameshift Mutagens: Metabolites and Derivatives of 2-acetylaminofluorene and other Aromatic Amine Carcinogens". PNAS 69: 3128-2132. PDF
>Bruce N. Ames, Frank D. Lee, and William E. Durston (1973). "An Improved Bacterial Test System for the Detection and Classification of Mutagens and Carcinogens". PNAS 70: 782-6. PDF
>Joyce McCann, Neil E. Spingarn, Joan Kobori, and Bruce N. Ames (1975). "Detection of Carcinogens as Mutagens: Bacterial Tester Strains with R Factor Plasmids". PNAS 72: 979-83. PDF
>Bruce N. Ames, William E. Durston, Edith Yamasaki, and Frank D. Lee (1973). "Carcinogens are Mutagens: A Simple Test System Combining Liver Homogenates for Activation and Bacteria for Detection". PNAS 70: 2281-5. PDF