Auckland Cancer Society Research Centre

Mutagen testing services

We use the AMES bacterial reverse mutagenicity test, which can capture frame-shift mutagens (through S. typhimurium strain TA98 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. An important feature of this assay is that its sensitivity is enhanced as bacteria actively divide in the presence of the test substance. DNA damage therefore occurs during DNA replication, increasing the probability that errors (mutations) will occur.

Salmonellae 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 experiment. This consists of a post-mitochondrial supernatant (“S9”) of homogenised liver tissue, 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 on by Prival and Dunkel (1989). 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 have their products tested for mutagenicity.

For mutagen testing services contact:

Dr Nishi Karunasinghe
Research Fellow
Phone: +64 9 923 4609