COMPARISON OF SALMONELLA-TYPHIMURIUM TA102 WITH ESCHERICHIA-COLI WP2 TESTER STRAINS

In 1982, Levin et al. published a paper describing a new Salmonella typhimurium strain, TA102, for detecting mutagenic agents that react preferentially with AT base pairs. This strain has an AT base pair at the critical mutation site within the hisG gene, which is located on a multicopy plasmid, pAQ1; the chromosomal copy of the hisG gene has been deleted. It also has an intact excision repair system, thus facilitatin the detection of cross-linking agents, and carries the mutator plasmid, pKM101. Although TA102 has been shown to be reverted by certain mutagenic agents that are not detected in the usual battery of strains (TA1535, Ta1537, TA1538, TA98 and TA100), there has been a general reluctance within the field to include TA102 as one of the standard screening strains. This may in part result from the difficulties which have been experienced in many laboratories in maintaining the strain, and in obtaining reproducible spontaneous and induced revertant counts. At Glaxo we routinely include certain Escherichia coli strains in our mirobial test battery, and were aware that some of the genetic features offered by TA 102 were already being covered by these strains. For examples, E. coli WP2 (pKM101) has an AT base pair at the critical mutation site within the trpE gene, is excision proficient (and thus will detect cross-linking agents) and carries the pKM101 plasmid to enhance error-prone repair. From the published literature it was apparent that a number of the 'TA102 specific' mutagens could be detected in E. coli e.g. neocarzinostatin, UV and 8-MOP plus UV. We have expanded this data base by comparing the activity of nine 'TA102 specific' mutagens (cumene hydroperoxide, hydrogen peroxide, phenylhydrazine, glutaraldehyde, formaldehyde, Danthron, bleomycin, streptonigrin and mitomycin C) in plate incorporation assays using S.typhimurium TA102, and E. coli WP2 (pKM101) and E. coli WP2 uvrA (pKM101). The results obtained indicate that these E. coli strains, used in combination, will detect a similar spectrum of mutagens as TA102. © 1990 Oxford University Press.