Mutagenesis by ethidium bromide, proflavine and mitomycin C in the cyanobacterium Nostoc sp.

Abstract

Ethidium bromide, proflavine, and mitomycin C were strongly lethal but weakly mutagenic to the cyanobacterium Nostoc sp. With a view to studying the mode of action of these weak mutagens, their binding to Nostoc DNA was studied. The spectral changes resulting from the binding of these mutagens to the DNA in vitro indicated that probably only electrostatic forces may be involved in the mutagen-DNA binding. A similar low level of DNA binding in vivo would explain the weakly mutagenic action of the dyes observed. Since the dyes do not effectively intercalate into DNA, they may not be effective in inducing frameshift mutations but still can interfere with replication and/or transcription of the DNA.