Visible light mutagenesis in Escherichia coli.

Visible light (450 nm) caused base-pair substitution and frameshift mutations in Escherichia coli. Using the defined trpA reversion system, we showed that visible light induced transversions at both A:T and G:C sites although some base-pair substitutions were refractory to light-induced mutagenesis, possibly because of their location. The presence of R plasmid pKM101 caused a greater than additive increase in light-induced base-pair substitutions for some trpA alleles. Visible light mutagenesis was reduced but not abolished in a recA56 background, suggesting that more than one mutational mechanism may be operative.