Ames in s to determine if a chemical at hand is a mutagen. To determine the mutagenic activity of chemicals by observing whether they cause mutations in sample bacteria. If the test sample causes this reversion, it is a mutagen. I Isolate an auxotrophic strain of Salmonella Typhimurium for histidine. II Prepare a test suspension of his-ve Salmonella Typhimurium in a plain buffer with test chemical eg. Also add a small amount of histidine. Note: small amount of histidine is required so bacteria starts growing.
Once histidine is depleted only those bacteria mutated to gain the ability to synthesize histidine form colonies. Tablet, Bone implants etc. Please contact us to discuss about this. Contact Us. Data Access. End of Year Schedule Melbourne. End of Year Schedule Sydney. Both histidine and dipeptides that can be converted to histidine can potentially interfere with the Ames test by increasing the number of spontaneous revertants. Such interference might be especially evident when urine and other biological samples are studied in this assay.
Genotypes of bacterial strains widely used in the Ames test. Unlike mammals, these bacteria lack the necessary oxidative enzyme systems for metabolizing foreign compounds to electrophilic metabolites capable of reacting with DNA. The bacteria are therefore treated with the test compound in the presence of a post-mitochondrial supernatant 'S9' or 'microsome fraction' prepared from livers of mammals usually rats. Bacteria, the test compound and S9 mix are added to molten, diluted agar 'top agar' to which a trace of histidine has been added which is then mixed and poured onto the surface of a minimal-agar plate containing glucose 'bottom-agar'.
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