Effects of Salmonella genotypes and testing protocols on H2O2-induced mutation

Area of Science:

• Microbiology
• Genetics
• Toxicology

Background:

• Hydrogen peroxide (H2O2) is a reactive oxygen species with known mutagenic potential.
• Standard Salmonella typhimurium strains (TA100, TA102, TA104) are used for detecting mutagens, particularly oxidative mutagens.

Purpose of the Study:

• To evaluate the mutagenicity of hydrogen peroxide (H2O2) in various Salmonella typhimurium strains.
• To assess the responsiveness of a newly constructed strain, SB1106p, to H2O2-induced mutations.

Main Methods:

• Bacterial mutagenicity assays were performed using multiple Salmonella typhimurium strains, including TA97, TA100, TA102, TA104, SB1106, SB1111, and the newly constructed SB1106p.
• Both liquid pre-incubation and standard plate incorporation procedures were employed.
• Mutational analysis focused on revertant fractions, particularly intragenic deletions.

Main Results:

• Hydrogen peroxide demonstrated mutagenicity across several Salmonella typhimurium strains.
• Strain SB1106p, carrying a histidine mutation at a UGA chain-terminating codon, exhibited greater responsiveness to H2O2 than strains TA104 and TA102.
• Intragenic deletions were the predominant mutation type in TA104 exposed to H2O2; strains TA97, SB1111, and SB1106 showed clear positive responses, while TA100's response was variable.

Conclusions:

• The study confirms the mutagenicity of hydrogen peroxide in Salmonella typhimurium.
• The newly developed strain SB1106p is a sensitive tool for detecting H2O2-induced mutagenicity, outperforming existing strains like TA102 and TA104.
• Catalase levels did not correlate with the observed strain-specific responses to H2O2.