Ames test

Virtualab Protocols (Chang Bioscience)
S. typhimurium Strain Salmonella strains TA97, TA98, TA100, TA102, TA104, TA1535 and TA1537 are histidine auxotrophs. Both frameshift (e.g., TA98, TA1537) and base-pair substitution (e.g., TA102, TA100, TA1535) are presented. Additional markers (e.g, uvrB, rfa, pKM101 R factor plasmid) make the test more sensitive to certain types of mutagens.

Revertants are identified as colonies that grow in the presence of low levels if histidine.


1. Grow Salmonella culture in 2.5% Oxoid Nutrient Broth #2 at 37 C overnight with shaking.

2. Mix 5 ml test chemical, 50-100 ml Salmonella culture and 50 ml 10% S9 (Aroclor 1254-induced rat liver S9).

3. Incubate at 37 C for 20 minutes without shaking.

4. Add 2.0 ml of molten top agar (0.8% agar, 0.5% NaCl supplemented with histidine and biotin) and pour onto the Vogel-Bonner plates ( 1.5% agar, 2.0% glucose in Vogel-Bonner medium E (40 mM MgSO4, 520 mM citric acid, 2.87 M K2HPO4, 0.87 M NaHNH4 and autoclaved)).

5. Incubate at 37 C for 2 days.

6. Score for positive colonies.

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