Bacterial melanin interacts with double-stranded DNA with high affinity and may inhibit cell metabolism in vivo.

Melanin has been found to interact with a number of molecules including metal ions, antibiotics and proteins. In this study, we showed how melanin from bacteria can interact with double-stranded DNA. Investigation using capillary electrophoresis, various spectroscopic techniques and circular dichroism found that melanin interacts with DNA by intercalating between the base pairs of DNA. And this was further supported by simulating different forms of melanin docking to oligonucleotides. Transmission electron microscopy of recombinant Escherichia coli producing melanin suggested the interaction in vivo. Furthermore, we showed how the cytoplasmic localization of melanin may provide a novel function in inhibiting cellular metabolism using microcalorimetry. The implications of the interaction in prokaryotes and eukaryotes were discussed.