Effect of near-UV light on Escherichia coli in the presence of 8-methoxypsoralen: wavelength dependency of killing, induction of prophage, and mutation.

Wavelength dependency of photo-inactivation and photoinduced reverse mutation of Escherichia coli sensitized with 8-methoxypsoralen, and wavelength dependency of photoinduction of lambda prophage from the sensitized lysogen were measured in a range of 298 to 400 nm. The most efficient sensitization for these biological effects was observed between 320 and 340 nm. In the presence of 8-methyoxypsoralen, the induced mutation frequency per lethal hit was highest of 298 nm in the range examined and was gradually decreased with increasing wavelength to a minimum frequency at 345 nm. This finding may be a reflection of the production of more than one type of lesions which have different efficiencies for mutation compared with the killing efficiency.