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We have isolated an Escherichia coli tester strain for the use in mechanistic and metabolic studies of genotoxins. We started with one of the more used and better characterized E. coli K-12 laboratory strains, AB1157. We isolated a lipopolysaccharide defective mutant of strain AB1886 which is an excision repair deficient derivative of AB1157 and introduced a newly constructed plasmid pKR11, encoding mucAB, resulting in strain MR2101/pKR11. A genotoxicity assay was designed, monitoring the reversion to arginine prototrophy and a preliminary validation was carried out against Ames tester strain TA100 with a set of diagnostic compounds. The results seem to indicate that strain MR2101/pKR11 is an adequate tester strain which can be a useful tool in mechanistic studies. Moreover, this strain can serve as mother strain to isolate improved and more specialized tester strains.

Original publication




Journal article


Mutat Res

Publication Date





99 - 109


Dose-Response Relationship, Drug, Escherichia coli, Lipopolysaccharides, Mutagenicity Tests, Mutagens, Operon, Polysaccharides, Bacterial, Reproducibility of Results, SOS Response, Genetics, Salmonella typhimurium, Transduction, Genetic