Nitrofuran reductase activity in nitrofurantoin-resistant strains of Escherichia coli K12: some with chromosomally determined resistance and others carrying R-plasmids

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Abstract
The nitrofuran reductase activity of Escherichia coli K12 strains was separated into two components by passage through Sepharose 4B-200. The components differed in their sensitivity to 2 M urea and their reactivity with NADH and NADPH. Some nitrofurantoin-resistant mutants had lost one component (α) while retaining the other (β). Other mutants, resistant to higher levels of nitrofurantoin, had lost most of the β component as well. Transconjugants which had received plasmids conferring nitrofurantoin resistance were found to have only the a component and it was markedly less active when NADH rather than NADPH was supplied as co-enzyme.