Effects of plate preparation on results in microbial mutation assays.

Glucose autoclaved in an alkaline phosphate solution (heated glucose+salts, HGS) results in the production of a moiety that is nonmutagenic but can interact with a series of 4-[2-(aryl)ethenyl]-2,6-dimethylphenols to result in an increase in bacterial revertants that is dependent on the amount of HGS in the minimal agar plates. The reaction between the HGS and the chemical to form a mutagen is independent of the presence of bacteria, does not result in a nutritive analog to enhance growth of the auxotrophic bacteria, and is effective only in Salmonella typhimurium and Escherichia coli strains that contain the plasmid pKM101. A sufficient amount of this glucose product may be formed in normal plate preparation to produce apparent mutagenic activity of these chemicals.