Iron enhances the bactericidal action of streptonigrin.

Abstract The lethal action of streptonigrin on strains of Escherichia coli is greatly enhanced by citrate (10 −2 M). Desferrioxamine (2×10 −4 M), when added with streptonigrin and citrate, eliminates the citrate enhancement. These observations point to a role for iron in the bactericidal mechanism of streptonigrin. Extracellular citrate is known to promote the acquisition of iron by E. coli by delivering it as a ferric citrate complex to a specific transport apparatus on the cell envelope. Therefore, it may promote action of streptonigrin by increasing the intracellular concentration of available iron. Desferrioxamine, which forms a much stronger complex with ferric ion than does citrate, would be expected to suppress the ferric citrate effect, and this was observed.