title: Evaluation of Escherichia coli K-12 343/113 and derived strains for microbial mutagenicity assays.
abstract: Several characteristics of the E. coli K-12 mutagenicity tester strains 343/113 and 343/120 have been investigated for their effects on induced mutagenesis using the arg56 and nad113 genes, and resistance to valine. We found, as have earlier authors, that the nad113 marker is relatively specific for detecting frameshift-inducing mutagens and relatively insensitive to agents that cause point mutations. In contrast, both the Arg and Val markers are primarily specific for reversion (or mutation) induction by point mutagens. In all cases tested, the Arg and Val markers respond to mutagens in a qualitatively similar manner. We have enhanced the sensitivity of this tester system to a wide variety of mutagens by permeabilization of the tester cell population using Tris-EDTA treatment. This treatment prior to mutagen exposure enables the detection of mutagenicity of several compounds that are weakly mutagenic or nonmutagenic in untreated cells. We have also increased the mutagenicity of some chemicals by preincubating with rat-liver S9 at pH values other than 7.4. For diethylnitrosamine, for instance, maximal induction occurred at pH 6.5, and for benzo[a]pyrene, maximal induction was at pH 6.8.
mesh_terms: D001120:Arginine / Q000235:genetics; D002463:Cell Membrane Permeability / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004492:Edetic Acid / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D005690:Galactose / Q000235:genetics; D005796:Genes; D005809:Genes, Regulator; D006863:Hydrogen-Ion Concentration; D009152:Mutagenicity Tests / Q000379:methods*; D009153:Mutagens
chemical_list: D009153:Mutagens; D001120:Arginine; D004492:Edetic Acid; D005690:Galactose