Overview of Ames Test

The AMES streamlet also k instantlyn as bacteria converse mutation assay is employ to evaluate the mutagenic properties of test articles. The test was showtime developed by Bruce Ames in 1974 (Krebsfaenger). The amino acid low-level strain of S. typhimurium and E. coli be used in this experiment where in the absence of the external histidine source, the cells cannot get under ones skin to form colonies. Specifically these strains of Salmonella are defective in 1. ) Repair of mutations (uvrB) and 2. A rfa mutation (eliminating a portion of lipolysaccharide (a coating of outside bacterial surface)). The rfa mutation here fulfills two purposes 1. ) Helps Salmonella in takeing in presence of sodium desoxycholate or crystal violet. and 2. ) Increases the cell permeability allowing to a greater extent mutagen to enter the cell. The lack of uvrB gene in the decreases the rate of repair weapon of mutations occurring resulting in the increased incidences of occurring mutations. Thes e auxotrophic strain cannot grow on the media without histidine and biotine (due to uvrB).If these organisms are allowed to grow on the media lacking both of these, the strain get converted to prototroph resulting the organisms to grow on the mutagenic chemicals to be tested in the media. If the chemical universe tested is mutagenic, the organisms will grow as some substance are cap competent of causing mutations in the cells at same site or at nearby sites resulting in restoring genes function and these mutations in the cells can give back the gene regaining its function (Tejs).These revertant cells are thus able to grow on the media which does not contain histdine as it can now synthesize histidine on its own. This mutation attains the cells to divide continuously. If there is no moreover mutation occurring in the cell, the cells will die out like expression cell. But if any further mutation occurs which allows the cells to grow for many generations, then the cancerous cells will be formed. The principle of Ames test is specifically found on the hypothesis that any substance that is mutagenic for the bacteria used in this test may also turn out to be carcinogenic (compound causing cancer).The most important limiting points of the Ames test includes first an assumption that though Ames test is being tested on procaryotic microorganisms, it will detect the mutagens or cancer causing agents in military man beings. (Though this test uses rat liver enzymes, Ames test is not able to serve the perfect model for human beings. ) Secondly, mutagens found by this test mogul not be carcinogenic i. e. further test may be required. also all carcinogens are not mutagens ( i. e. Ames test is unable to project such agents eg asbestos).Third, some nitrate containing compounds lie nitroglycerine can cause false positive production by producing nitric oxide. ? Works Cited 1. Krebsfaenger, Niels. AMES test Bacterial Reversed Mutation Assay. Genpharmtox, Assay Sheet A MES TEST. Gen Pharm Tox, n. d. Web. 21 Nov 2012. . 2. Tejs, Sebastian. The Ames runnel A methodological Short Review. Environmental Biotechnology. Environmental Biotechnology, University of Warmia and Mazury, n. d. Web. 27 Nov 2012. . 3.