A strong lethal interaction was observed between various monochromatic wavelengths (254, 334, 365, and 405 nm) in the repair-proficient E. coli K-12 strain AB 1157, except in the case of preexposure to 405-nm radiation which resulted in a protection against the inactivation resulting from subsequent exposure to 365or 254-nm radiations. The results may be tentatively explained by assuming two classes of DNA lesions and two classes of damage to repair (reversible and irreversible) whose

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... s vary according to wavelength. on May 9, 2020 by guest http://jb.asm.org/ Downloaded from 416-420. 15. Ying, C. Y., J. A. Parrish, and M. A. Pathak. 1974. Additive erythemogenic effects of middle (280-320 nm) and long (320-400 nm) wave ultraviolet light.