WORLD OF MICROBIOLOGY AND IMMUNOLOGY Ames, Bruce N.13•
The present facility is 106,000 square feet in size and
has almost 35,000 square feet of laboratory space, including
specialized containment facilities for more hazardous house
microorganisms. Over fifty ultra-low temperature freezers are
used for the long-term storage of samples. Such storage avoids
changes in the organisms that could result from storage at
refrigeration temperatures.See alsoCryoprotectionAAmes, Bruce N.MES, BRUCEN.(1928- )
American biochemist and molecular biologistBruce N. Ames is a professor of biochemistryand molecular
biologyat the University of California at Berkeley. He is best
known for the development of a test used as an indicator of the
carcinogenicity (cancer-causing potential) of chemicals.
Known as the Ames test, it measures the rate of mutation in
bacteriaafter the introduction of a test substance. Ames’s
research led to a greater appreciation of the role of genetic
mutation in cancer and facilitated the testing of suspected can-
cer-causing chemicals. He also developed a database of chem-
icals that cause cancer in animals, listing their degree of
virulence. Ames has been involved in numerous controversies
involving scientific and environmental policies relevant to
cancer prevention. In the 1970s he vociferously advocated
strict government control of synthetic chemicals. In the 1980s,
however, the discovery that many natural substances were also
mutagenic (causing genemutation), and thus possibly cancer
causing, led him to reverse his original position.
Ames was born in New York City, the son of Dr.
Maurice U. and Dorothy Andres Ames. His father taught high
school science and then became assistant superintendent of
schools. Ames himself graduated from the Bronx High School
of Science in 1946. He received a B.A. in biochemistry from
Cornell University in 1950 and a Ph.D. in the same field from
the California Institute of Technology in 1953. Ames worked
at the National Institutes of Health, primarily in the National
Institute of Arthritis and Metabolic Diseases, from 1953 to- In 1968 he moved to the Department of Biochemistry
and Molecular Biology at the University of California at
Berkeley as a full professor. He was Chairman of the
Department from 1984 to 1989. In addition he became
Director of the National Institute of Environmental Health
Science at the University in 1979.
In the 1960s and early 1970s Ames developed a test
that measured the degree to which synthetic chemicals cause
gene mutation (a change in the deoxyribonucleic acid, or
DNA, the molecule that carries genetic information). He
began by deliberately mutating a Salmonellabacterium. The
changed bacterium could not produce an amino acid called
histidine that normal bacteria produce and that they need to
survive. The next step was to add just enough histidine to
allow the bacteria to live, and to add, as well, the synthetic
chemical being tested. If the added chemical caused genetic
mutation, the abnormal gene of the Salmonella bacteria
would mutate and again be able to produce histidine. When
this happened the added chemical was marked as a suspected
carcinogen, because cancer is associated with somatic cell
mutation (that is, mutation of any cells with the exception of
germ cells).
Over eighty percent of organic chemicals known to
cause cancer in humans tested positive as mutagens in the
test developed by Ames and his colleagues. This result gave
support to the theory that somatic mutation causes cancer
and helped to validate the use of the test for initial identifi-
cation of mutagens when considering synthetic chemicals for
industrial and commercial use. In addition to these practical
results, the research of Ames and a colleague, H. J.
Whitfield, Jr., led to important advances in understanding the
biochemistry of mutagenesis. Beyond his work in genetic
toxicology, Ames made important discoveries in molecular
biology, including ground-breaking studies on the regulation
of the histidine operon(the gene or locus of the gene that
controls histidine) and the role of transfer ribonucleic acid
(RNA) in that regulation.
In the 1980s Ames set up a database of animal cancer
test results with colleague Lois Swirsky Gold of Lawrence
Berkeley Laboratory. The database is used to determine
whether a chemical has tested positive as a carcinogen and
gives the degree of its virulence. From these data Ames
developed a value measuring the carcinogenic danger of
a chemical to humans. HERP (daily Human Exposure
dose/Rodent Potency dose) is the value determined by com-
paring the daily dose of a chemical that will cause cancer in
half a group of test animals with the estimated daily dose to
which humans are normally exposed. The result is a percent-
age that suggests the degree of carcinogenicity of a chemical
for humans.
In the 1970s Ames was a conspicuous advocate of par-
ticular regulatory and environmental public policies that relate
to the cancer-causing potential of synthetic substances. In the
1970s Ames asserted that even trace amounts of mutagenic
chemicals could cause a mutation (and thus possibly cancer).
He found that tris (2,3-dibromopropyl) phosphate, the chemi-
cal that was used as a flame retardant on children’s pajamas,
was a mutagen in the Ames test; he was instrumental in get-
ting it banned. Similarly he found that some hair dyes con-
tained mutagens. His advocacy led to governmental
regulations that forced manufacturers to reformulate their
products. In his position on the regulation of synthetic chemi-
cals, he was a natural ally of environmentalists.
However, in the early 1980s Ames reversed his position,
arguing that there is no scientific evidence that small doses of
most synthetic chemicals cause human cancers; he also argued
that, in the absence of such evidence, they should not be con-
trolled. This about-face was partly a result of a growing body
of knowledge concerning the mutagenic properties of numer-
ous chemicals found in nature. Ames began arguing against
the existing large public expenditures for pollution control and
the regulation of synthetic chemicals, noting that cancer might
just as plausibly be caused by the chemicals in plants. His
arguments were based primarily on three factors: his argument
that more scientific evidence should be required before con-
trols are implemented; his attitude toward the setting of prior-womi_A 5/6/03 1:06 PM Page 13