THE EFFECT OF PLASMID PKM101 ON UMUDC GENE-FUNCTION ENHANCING PRECISE EXCISION OF TRANSPOSONS

Mutation in the thr gene with the highest UV-induced reversion frequency has been chosen from a number of mutations arisen from insertion of transposon Tn10 into the umuDC- Salmonella typhimurium. This mutation has been transfered by transduction into the Salmonella strain carrying E. coli umuDC+ genes. umuDC- and umuDC+ Salmonella strains, bearing the same insertion mutation, were used to study the effec of umuDC genes and of plasmid pKM101 on spontaneous and UV-induced precise excision of Tn10. This process, like point mutagenesis, is shown ro be umuDC-stimulated. Plasmid pKM101 eliminates the effect of umuDC+ genes on UV-induced Tn10 precise excision, in contrast to its effect on point mutagenesis, and does not enhance spontaneous precise excision of Tn10. © 1990.