Influence of Monochromatic Ultra-violet Light on the Transformation Activity ofBacillus Subtilis

Abstract

Dose and wavelength dependence of the inactivation of transforming-DNA by ultra-violet radiation have been investigated. The extent of damage was measured on the transforming system of Bacillus subtilis, in which an indole-requiring strain was transformed to prototrophy by wild-type DNA. The quantum yield was found to be independent on wavelength in the range 240 ⩽ γ 300 mμ. Of the total number of inactivating lesions produced at the indole marker by 285 mμ radiation, none could be reversed by subsequent irradiation at 240 mμ. We conclude that cytosine is involved in the biological damage. The differences of the indole marker of Bacillus subtilis towards the inactivation of the streptomycin marker of Haemophilus influenzae are discussed.