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Mutagenicity Water and Solid Testing - Ames test

Ames Reverse Mutation Kit 1 Ames Test Reverse Mutation Kit Ames Test Reverse Mutation Assay Ames Test Kit

 

 

 

 

 


The Ames test is a bacterial assay to assess the potential of chemical compounds to cause mutations in genetic material and thus are potentially carcinogenic.  A positive test indicates that the chemical is mutagenic and may be a carcinogen. The test serves as a quick and convenient assay to estimate the carcinogenic potential of a compound as standard assays using animals are time-consuming (taking two to three years to complete) and expensive.

The Ames test uses several strains of the bacterium Salmonella typhimurium that carry mutations in genes coding for histidine biosynthesis. These strains are auxotrophic mutants that require histidine (or other amino acids) for growth. The method tests the capacity of a compound to create mutations that can result in a reversion back to a prototrophic state allowing the bacterium to grow on a histidine-free medium. The tester strains are specially constructed to detect frameshift or point mutations in the genes required to synthesize histidine.  However, the test does have its limitations.  For example, mutagens may act differently on the different strains used in the test. In addition, mutagens that do not cause frameshift or point mutations may not be detected.  Also, as Salmonella typhimurium is a prokaryote, it is not a perfect model for humans.  Additionally, some compounds are not mutagenic, but their metabolic products are.  In the latter case, rat liver extract is optionally added to simulate the effect of metabolism and conversion of the native compound in the hepatic system.

Mutagens identified in the Ames test need not necessarily be carcinogenic, and further tests are required to determine whether they are true carcinogens. For example, compounds that contain the nitrate moiety may show a positive result when they are indeed safe by generating nitric oxide, an important signal molecule that can result in a false positive. Nitroglycerin is an example that gives a positive Ames result yet is still used without concern of carcinogenicity. Additionally, chlorination compounds of high TOC water may also act as mutagens in the assay.

The Ames test was initially developed in the early 1970's (Ames et al., 1975 Mutation Research 31:347) using agar plates. Since then a higher throughput and more sensitive method has been developed using liquid media in a well plate format.  The sample is mixed with the bacteria and specific nutrients, placed into well plates and incubated. Any growth in the wells is observed via a color change (media turns from purple to yellow due to pH change) and is indicative of a reversion caused by a mutation. The greater the number of positive wells, the greater the mutagenic potential of a sample. This method allows for the testing of higher concentrations of sample, thus increasing the sensitivity (up to 10 times) and extending its application to low-level environmental mutagens.

BCS laboratories uses the  Muta-ChromoPlate kit for detection of the mutagenic potential of submitted water and solid (including soil and sediment) samples. Testing is performed following the OECD 471 Guidelines for Testing Of Chemicals - Bacterial Reverse Mutation Test.

The Salmonella strains commonly used  are TA97a and TA98, which code for frameshift mutations, and strains TA100, WP2, and TA1535, which code for base-pair substitution mutaions (base insertion, deletion, missence, nonsensence, and duplication) .  For a visual presentation describing the AMES reverse mutation assay utilized please click here.

Please contact BCS directly for appropriateness of the test, strains, applicability, and pricing.

 

 

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