School of Medical Sciences

AMES Bacterial Reverse Mutagenicity Test

An important feature of the Salmonella reverse mutagenicity assay is that it enhances its sensitivity as bacteria are actively dividing in the presence of the test substance. DNA damage therefore occurs during DNA replication, increasing the probability that errors (mutations) will occur.

Salmonella do not possess the enzyme systems which, in mammalian cells, are known to mediate the transformation of many classes of chemically unreactive chemicals to highly reactive electrophiles which can form adducts with nucleophilic sites in DNA (Miller and Miller, 1976). In order to overcome this major drawback, an “S9” mix can be added to the experiments. This consists of a post mitochondrial supernatant (“S9”) of homogenised liver tissue of rats, which contains a variety of drug metabolising enzymes. The S9 is supplemented with co-factors, salts and a buffer system, the complete preparation being known as the “S9-mix”.

The test in this laboratory is performed according to standard plating protocols, described by Maron and Ames (1983), incorporating recommendations from Dean (1983) and Ashby et al. (1985). Criteria for classification of results as positive or negative follow these authors, as expanded by Prival and Dunkel (1989).

This test can capture frame-shift mutagens (through S. typhimurium strainTA98 and TA1537), base-pair-substitution mutagens (through strain S. typhimurium TA100) or mutagens which act through the production of oxygen radicals (through strain S. typhimurium TA102). We maintain different strains of Salmonella typhimurium for this assay and the test is carried out according to the OECD guidelines for Testing of Chemicals No.471 (adopted since 21st July 1997).

The test is offered as a service at a nominal cost for those wishing to get their products tested for mutagenicity.



For Mutagen Testing Services contact:

Prof. Lynn Ferguson

Phone: +64 9 923 6372