Novel effect of aromatic compounds on the iron-dependent expression of theEscherichia coli K12 manganese superoxide dismutase (sodA) gene

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Abstract
InEscherichia coli, the superoxide dismutase genes (sodA andsodB) sense the availability of Fe through the action of thefur locus [E. C. Niederhoffer, C. M. Naranjo, K. L. Bradley, J. A. Fee (1990) Control ofEscherichia coli superoxide dismutases (sodA andsodB) genes by the ferric uptake regulation (fur) locus,J. Bacteriol. 172, 1930–1938]. Previous work from other laboratories has shown that a variety of metal chelators and of redox-active aromatic compounds can dramatically induce expression ofsodA. Here we show that non-redox-active, non-metal-chelating aromatic compounds also enhance expression of a chromosomalsodA gene fusion and that these effects are strongly modulated by the Fur phenotype (Fur±) and by the availability of iron in the culture medium. The compounds studied were ethidium bromide, hemin, 2,2′-bipyridine, 1,10-phenantroline, 4,7-phenantroline, rhodamine B1, rhodamine 6G, and, for comparison to previous studies, Paraquat.