Ames test technique problem

chenli s972198 at
Wed Nov 12 02:38:47 EST 1997

Hello everybody,
I got some problems in Ames test.
Firstly, I got very great variation in the testing results even only
DMSO was added. All the tests were in triplicate and the variations not
only happened in the series of test but also between the triplicates.
Those variation include (1) absent and present of background lawn. (2)
absent or present of mutate colonies, usually, this happen in the
triplicates e.g. 50, 0, 0. Although I got positive testing results of
the strains TA98 and TA100 before running experiment and followed the
protocols suggested in Mutation Research 113:173-215, the suitation
happened again and again. At the beginning, I wonder it might be due to
the toxicity of the standard mutagens I used, e.g. 2AAF. Therefore, I
turn my target to the solvent(DMSO)and set an experiment with excess
amount of histine or no histine was added in top agar in 'solvent' test.
It was found that bacteria TA98 grown same in both having DMSO and no
DMSO in excess amount of histine supplied but for TA100, bacteria grown
better in no DMSO. Whereas, in the absent of histine supplied, no
background lawn were form but there were about 1000 colonies in each
plates. It seem no colonies variation in triplicate. Then, I ran the
test again with different concentration of DMSO but the variations came
again. Therefore, I want you could give me some suggestions or ideas
about the test or what's possible mistake in the experiment. Looking
forwards to your reply. 
William Chan,
Dept. of Biology,
Chinese University of Hong Kong 
e-mail address: s962178 at

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