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THE DELTA UVRB MUTATIONS IN THE AMES STRAINS OF SALMONELLA SPAN 15-119 GENES
Citation:
Porwollik, S., R. Wong, R. M. Schaaper, D M. DeMarini, AND M. McClelland. THE DELTA UVRB MUTATIONS IN THE AMES STRAINS OF SALMONELLA SPAN 15-119 GENES. MUTATION RESEARCH 483(1-2):1-11, (2001).
Description:
Abstract
The 4uvrB mutationesent in strains of Salmonella enterica Typhirnurium used commonly in the Salmonella (Ames) mutagenicity assay were isolated independently on separate occasions: chl-1005 (bio uvrBgal) for the hisG46-containing strains TA1535 and TA100; chl- 1007 (bio uvrB gal) for the hisC3076-containing strain TA1537; and chl-1008 (bio llVrB gal) for the hisD3052-containing strains TAl538 and TA98. All were isolated as deletions involving the galactose operon, biotin operon, nucleotide-excision repair tlvrB gene, and chlorate-resistance genes. However, beyond this, the size of the deletions and the number and type of genes deleted have remained unknown for nearly 30 years. In the present study, we have used genomic hybridization techniques to characterize these three LtuvrB mutations. The numbers of genes (and amount ofDNA) deleted due to the LtuvrB mutations are 47 (50 kb) in TAl00, 87 (96 kb) in TA1537, and 121 (125 kb) in TA98, accounting for 1.0,1.9, and 2.6%.ofthe genome, respectively. Missing genes include mfd4 and mdaA, encoding a multi-drug translocase and a major nitroreductase, respectively, both absent in TA98; dps, encoding a DNA~binding protein absent in TA1537 and TA98; and dinG, encoding a lexA~regulated repair enzyme, absent in all three LluvrB lineages. Furthermore, genes involved in molybdenum cofactor biosynthesis and a number ofORFs ofunknown functions are missing in all LluvrB strains investigated. Studies in Ll,lVrB strains of Escherichia coli have found that the enhanced mutagenesis of some base analogues was due to the deletion of genes involved in molybdenum cofactor biosynthesis rather than to deletion of uvrB. Absence of genes other than uvrB may account for the enhanced mutagenesis of some compounds in 4uvrB Ames strains. In general, micro arrays may be useful for characterizing the extent and nature of deletion mutations.