When do you take the ames test?
The ames test is a basic toxicological test that can be used to
determine if a substance is potentially genotoxic. It is a very
easy and cheap test that can be set up in most labs. The test looks
for gene mutations in bacteria, normally Salmonella typhimurium. A
strain of S. typhimurium with a mutation that causes it to be
unable to synthezise histidine (amino acid) is plated along with
the substance to be tested. The mutation in the bacteria can easily
be backmutated, thus, any substance with a genotoxic (mutagenic)
ability can cause the bacteria to backmutate to a state where it
can again syntesize histidine. S. typh on agar plate without
histidine will not be able to grow, and thus, no colony forming
units (cfu) will be seen. S. typh on agar plate, add potentially
genotoxic substance onto agar (normally on paper disc), the
substance will filter through agar, and if mutagenic, can cause
backmutation in the bacteria which will then be able to synthesize
histidine, resulting in growt of cfu's. The results seen in the
ames test can give an idea of the substances potential for
genotoxicity. If the substance has the ability to cause a mutation
in the bacteria, it might be able to cause mutations in humans as
well, and should therefore undergo further testing to determine
whether it is safe or not.
