Ames test of mutagenicity

Bruce N. Ames
Senior Scientist, Children's Hospital Oakland Research Institute, Oakland, California, and Professor Emeritus, Biochemistry and Molecular Biology, University of California Berkeley, Berkeley, California, USA

Ames is suggested as a possible Nobel Prize winner “for the invention of the Ames test of mutagenicity”

When it became apparent that cancer could be triggered by certain chemicals, a way was needed to check such chemicals before they were approved for use. Testing on animals was slow and expensive and required their exposure to unrealistic amounts of the compound under investigation. Positive findings from such testing invariably led to alarms in the media, and there was much ill-informed speculation about man-made chemicals being the cause of cancer in humans. This was particularly important with respect to chemicals that were being employed as pesticides, or in household chemicals, or used as food additives. Then along came a test devised by Bruce Ames, which changed everything.

The Ames test, as it became known, was quick, cheap and easy to carry out and did not involve animals. It relied on bacteria, and in particular the bacterium Salmonella typhimurium. With this test it became possible to screen large numbers of chemicals, both man-made and natural, and it gave reliable results. The Ames test was published in 1975 (Proc. Natl. Acad. Sci. USA, 72: 5135-9) and it was eventually to change attitudes to the extent that the all-embracing term “cancer-forming chemical” fell into disuse and is now rarely heard.

In subsequent years Ames refined his method. His most-cited paper, from 1983 (Mutation Research 113: 173-215), presenting revised methods for the Salmonella mutagenicity test, has now been referenced more than 5,200 times.

The Ames test extended its reach to involve natural chemicals, and consequently many of these were shown to have mutagenic activity, much to the surprise of those who were actively opposed to all things they described as “chemicals.”

Ames continued his research into mutagenicity and to link this to oxygen radicals, with the result that his 1983 paper on this subject has attracted 2,400 citations (Science, 221: 1256-64). His 1993 paper on the role of these radicals in the degenerative diseases of ageing has been referenced nearly 3,500 times (Proc. Natl. Acad. Sci. USA, 90: 7915-22).

Commentary on the Chemistry Laureates by John Emsley, Chemistry correspondent, ScienceWatch. Dr. Emsley is based at the Department of Chemistry, University of Cambridge, UK.