PHOTOREACTIVATION OF ESCHERICHIA COLI Bs-3 AFTER IN ACTIVATION BY 313 nm RADIATION IN THE PRESENCE OF ACETONE

Abstract— The colony-forming ability of E. coli B_s-3 can be inactivated by light of 313 nm wavelength in an acetone-sensitized photochemical reaction. This ability can subsequently be restored quantitatively by illumination with photoreactivating light. A small fraction of the population cannot be inactivated; this is assumed to be due to a complete dark repair of the lesions, whatever the dose of radiation has been. Thus, such triplet energy-transfer experiments can successfully be applied to whole cells. Since thymine dimers are formed almost exclusively, this suggests a new way of studying these lesions in relation to the biologically observable effects.