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JOURNAL OF BACTERIOLOGY, Nov. 1986, p. 795-798 Vol. 168, No. 2 0021-9193/86/110795-04$02.00/0
 

Summary: JOURNAL OF BACTERIOLOGY, Nov. 1986, p. 795-798 Vol. 168, No. 2
0021-9193/86/110795-04$02.00/0
Copyright 1986, American Society for Microbiology
Paraquat-Mediated Selection for Mutations in the
Manganese-Superoxide Dismutase Gene sodA
CRAIG A. BLOCH* AND FREDERICK M. AUSUBEL
Department of Genetics, Harvard Medical School, and Department ofMolecular Biology, Massachusetts General
Hospital, Boston, Massachusetts 02114
Received 19 May 1986/Accepted 21 July 1986
We report the unexpected result that Escherichia coli isolates containing a multicopy plasmid (pDT1.5)
carrying the manganese-superoxide dismutase gene sodA were more sensitive than the wild type to paraquat-
mediated growth inhibition. The pDTl.5 locus responsible for the paraquat-sensitive phenotype was delimited
to a 0.6-kilobase segment by transposon Tn5 mutagenesis. Moreover, superoxide dismutase activity was the
same as in the wild type in strains carrying pDT1.5::TnS insertions mapping to the 0.6-kilobase locus. These
data identify the 0.6-kilobase segment as the locus of sod4 and establish an association between growth
inhibition by paraquat and the function of the plasmid-borne sodA gene.
Paraquat (1,1'-dimethyl-4,4'-bipyridinium dichloride) is
thought to undergo oxidation-reduction cycling within cells,
thereby generating intracellular superoxide radicals (5, 11)
which may be toxic to cells at high concentrations. Manga-

  

Source: Ausubel, Frederick M. - Department of Genetics, Harvard University

 

Collections: Biology and Medicine