Abstract
We investigated the role of the umuDC and samAB operons in the UV mutability of Salmonella typhimurium. umuDC is located on the chromosome, whereas samAB resides on the virulence plasmid pSLT. Using allele replacement and plasmid curing techniques, we found that UV mutability was eliminated when any of three different umuDC alleles (umuD1, umuC1, or umuD1 umuC1) were on the chromosome even when samAB was present. We conclude that samAB normally does not complement umuDC function in S. typhimurium.