Extreme cold sensitivity of Salmonella typhimurium umu clones, effects of the umu region and flanking sequences.
The umuDC operons of both Salmonella typhimurium and Escherichia coli encode proteins which are essential for mutagenesis following exposure to ultraviolet radiation or a variety of chemicals. However S. typhimurium is less mutable and its umu operon appears to be less active for reasons that are unknown. This study shows that pBR322-based plasmids carrying cloned umuDC operons of either species confer cold sensitivity on both an E. coli umuC strain and a S. typhimurium pSLT- strain. Both S. typhimurium and E. coli umu clones make these lexA+ strains moderately cold-sensitive, but sensitivity produced by the cloned S. typhimurium umuDC operon is extreme when flanking regions of the chromosome are also present. Such instability might be significant in terms of explaining the polymorphisms seen in the regions of the chromosomes of Enterobacteriaceae surrounding the umuDC operon. In S. typhimurium this extreme cold sensitivity was almost certainly responsible for the delayed recognition of a chromosomal umuDC operon.
Thomas
S M
SM
School of Biological Sciences, Flinders University of South Australia, Bedford Park.
D003080:Cold Temperature; D004926:Escherichia coli / Q000235:genetics; D009154:Mutation; D009876:Operon; D010957:Plasmids; D012486:Salmonella typhimurium / Q000235:genetics* / Q000502:physiology