Action spectrum for growth delay induced in Escherichia coli B-r by far-ultraviolet radiation.

An action spectrum for growth delay induced in Escherichia coli B/r by far-ultraviolet radiation (230 to 295 nm) was obtained. It resembles the action spectrum for killing obtained in the same experiments, indicating that the chromophore for growth delay is probably the same as the chromophore for killing. Another action spectrum for killing, obtained under conditions more suitable for chromophore identification, suggests that nucleic acid, either deoxyribonucleic acid or ribonucleic acid, is the chromophore for growth delay induced by far ultraviolet. Isoprenoid quinones, which seem to be important chromophores for growth delay induced by near-ultraviolet radiation (above 300 nm), appear to play a negligible role in growth delay induced by wavelengths below 300 nm.