Effect of passage number on the activity and spontaneous reverse mutation of Ames test strains / 上海预防医学

ABSTRACT

Objective We explored the stability of the bacteria strains used in the Ames test to provide a basis for determining the appropriate passage number at which the biological characteristics of the strains would not change. Methods The Salmonella typhimurium (TA97a, TA98, TA100 and TA102 strains) were selected as the experimental strains.The original frozen strains and frozen strains with different passage times were used to compare the biological characteristics and the spontaneously reverting colonies. Results The biological characteristics of four kinds of strains, which were histidine deficiency, lipidpolysaccharide barrier defect, ampicillin resistance, UV sensitivity, and tetracycline resistance, did not change at F1-F6 generation when compared with the F0 generation.However, as for the number of spontaneously reverting colonies, a statistically significant difference (P < 0.05) occurred at F3 generation when compared with F0 generation for the TA97a strain, and a significant difference (P < 0.05) occurred at F4 generation for TA100 and TA102 strains. Conclusion Passage number of strains used in Ames test could affect their spontaneous reversion mutation rate.The passage number should be less than 4 for TA98、TA100、TA102 strains, and less than 3 for TA97a in Ames test.