Effects of near-ultraviolet and violet radiations (313-405 nm) on DNA, RNA, and protein synthesis in E. coli B/r: implications for growth delay.

Abstract

Abstract— Fluences (21–32 kJ/m2) of near‐ultraviolet radiation that induce about a 1‐h growth delay in continuously growing cultures of E. coli B/r are found to produce complete cessation of net RNA synthesis, while the effects on protein and DNA synthesis are considerably milder. The near‐UV action spectrum for this inhibition of RNA synthesis is similar to the action spectrum for growth delay in E. coli B and to the absorption spectrum of E. coli valyl transfer RNA. In addition, the fluences required for inhibition of RNA synthesis and for growth delay are similar to those reported for formation of 4‐thiouridine‐cytidine adducts in transfer RNA. These findings suggest that the chromophore and target for near‐UV‐induced inhibition of both net RNA synthesis and growth in E. coli may be 4‐thiouridine in transfer RNA.