Isolation and prevalidation of an Escherichia coli tester strain for the use in mechanistic and metabolic studies of genotoxins.

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.