Influence of S9 mix on the expression of mutants in the L-arabinose resistance test of Salmonella typhimurium.
S9 mix produces an effect similar to that of D-glucose in the L-arabinose resistance test of Salmonella typhimurium, releasing the growth inhibition exerted by L-arabinose. Two elements are responsible for this effect: the glucose-6-phosphate present in the cofactors of the S9 mix and the S9 fraction itself. UV light was used as a mutagen to compare the efficiency of S9 mix and D-glucose in allowing phenotypic expression of mutants in selective plates with L-arabinose; 0.5 ml of S9 mix per plate showed and efficacy similar to that of 0.5 mg of D-glucose per plate. To verify that the S9 mix is equivalent to D-glucose traces in selective plates with respect to the number of induced mutants in compounds requiring metabolic activation, we utilized 2 direct-acting nitrofurans. Our conclusion is that activation of agents could be erroneously attributed to the S9 mix, when plates with 0.5 mg of D-glucose are compared to plates with 0.5 ml of S9 mix plus 0.5 mg of D-glucose. Our results suggest that D-glucose traces be omitted in experiments requiring the presence of the S9 mixture.
Roldán-Arjona
T
T
Departamento de Genética, Facultad de Ciencias, Universidad de Córdoba, Spain.
Ruiz-Rubio
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M
Pueyo
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C
D000818:Animals; D001089:Arabinose / Q000494:pharmacology*; D003470:Culture Media / Q000494:pharmacology*; D004352:Drug Resistance, Microbial / Q000235:genetics; D015870:Gene Expression; D005947:Glucose / Q000494:pharmacology; D008099:Liver / Q000201:enzymology; D009152:Mutagenicity Tests; D009153:Mutagens / Q000378:metabolism*; D009154:Mutation; D051381:Rats; D012486:Salmonella typhimurium / Q000187:drug effects / Q000235:genetics*; D014466:Ultraviolet Rays
D003470:Culture Media; D009153:Mutagens; D001089:Arabinose; D005947:Glucose