Ineffectiveness of rifampicin in inhibiting RNA synthesis in Escherichia coli and T(4)-infected Escherichia coli cells after exposure to ultraviolet radiation.

Resdiual RNA synthesis in Escherichia coli cells and T(4)-infected E. coli cells exposed to ultraviolet radiation is insensitive to rifampicin. On the other hand, residual RNA synthesis in these cells after gamma irradiation is further inhibited by rifampicin. The specific effect exerted by ultraviolet irradiation on transcription seems to arise from alterations in the DNA structure rather than in bacterial RNA polymerase since RNA synthesis in ultraviolet-irradiated E. coli cells infected with unirradiated T(4) is sensitive to rifampicin.