MUTABILITY OF SALMONELLA TESTER STRAINS TA1538 (HISD3052) AND TA1535 (HISG46) CONTAINING THE UMUD' AND UMUC PROTEINS OF ESCHERICHIA-COLI

We have studied the mutability of Salmonella typhimurium tester strain s carrying plasmids in which either the umuDC or the umuD'C operon of Escherichia coli have been cloned. Reversion of the hisD3052 frameshif t mutation by benzo[a]pyrene (B[a]P), aflatoxin B1 (AFB1) and l-nitrop yrene (1-NP), was very efficiently promoted by UmuD' (the activated fo rm of UmuD) and UmuC proteins. In contrast, UmuD'C proteins promoted a moderate reversion of the missense hisG46 allele by B[a]P, and were n ot effective in mediating this reversion by AFB1. The Salmonella teste r strain carrying the hisD3052 allele and containing the E. coli UmuD' C proteins has a sensitivity toward frameshift mutagens similar to tha t of the MucAB containing strain TA98, and may be useful for obtaining a high level of mutants generated by the SOS mutagenic mechanism in t he absence of MucAB proteins. (C) 1994 Wiley-Liss, Inc.