Genetic differences between the standard Ames tester strains TA100 and TA98

Area of Science:

• Microbiology
• Genetics
• Toxicology

Background:

• Standard Ames tester strains of Salmonella typhimurium possess complex genetic histories.
• These strains contain independently isolated mutations (uvrB-bio-gal deletions and rfa mutations).

Purpose of the Study:

• To investigate the impact of the araD531 mutation on Ames tester strains TA100 and TA98.
• To assess the responsiveness of modified strains (BA15 and BA14) to chemical mutagens using an L-arabinose resistance assay.

Main Methods:

• Introduction of the araD531 mutation into Ames strains TA100 and TA98.
• Assessment of mutagen-induced forward mutations to L-arabinose resistance (Ara test).

Main Results:

• Strains BA15 and BA14 exhibited significant differences in mutagen response, independent of his mutations.
• Strain TA100 showed higher sensitivity to chemical killing effects compared to TA98.
• The Ara test detected mutagenic effects of nifurtimox and compound 1K in TA98 but not in TA100.

Conclusions:

• Standard Ames Salmonella typhimurium tester strains are not isogenic.
• Genetic variations beyond his mutations can significantly influence mutagenicity testing outcomes.
• Differences in nitro-reduction capability and sensitivity to lethal effects may explain strain-specific responses.