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

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 (a) while retaining the other (ß). Other mutants, resistant to higher levels of nitrofurantoin, had lost most of the ß 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.