AMES testing is used for detecting mutagens in samples, including test extract from plumbing products in contact with drinking water, using Salmonella typhimurium histidine (His) reversion system, which involves mutation of the histidine locus in the genome of several strains.

 

Abbreviated assays are available for certain situations, for example the modified AMES Oil test and Mutagenic Activity of Water Extract test ( AS/NZS 4020).

 

The reverse mutation assay mutation in a gene of an amino acid-requiring bacterial strain, the result of which is to produce an amino acid-independent strain. For S.typhimurium, it detects a mutation which is in a histidine-dependent strain to produce a histidine-dependent strain to produce a histidine-independent strain. Each tester strain contains a different type of mutation in the histidine operon.

 

The mutagenicity assay relies upon treating the bacteria with test material over a range of doses immediately below the concentration showing significant toxicity to bacterial. Treated bacteria are then grown on agar plate deficient in histidine. The original mutated Salmonella (histidine-dependent) cannot form visible colonies under such growth conditions, unless they undergo a second mutation and revert back to histidine-independent. After the treatment of the test material, the number of such revertant colonies per agar plate could be used as an indicator of the mutagenic potency of the test material.

 

For rountine mutagenicity testing, the Salmonella tester strains recommended are TA97a, TA98,TA100,TA102 and TA1535.TA1535 is optional, and TA1537 is replaced by TA97a.