DARK REPAIR OF ACRIDINE DYE-SENSITIZED PHOTOEFFECTS IN E COLI CELLS AND BACTERIOPHAGE

Bacteria and phages can be inactivated by visible light in the presence of sensitizing dyes and oxygen. The lesions, which are mainly due to effects in nucleic acid, are quite different from UV lesions not only in the physical-chemical changes brought about (e.g. FREIFELDER and URETZ, 1966), but also with respect to the biological effects produced: they are neither photoenzymatically repairable nor multiplicity-reactivable (WELSH and ADAMS, 1954). While recent work with E. coli and yeast cells suggest that the photodynamic lesions are also unaffected by enzymatic processes known to achieve extensive dark repair of UV lesions (e.g. URETZ, 1964; FREIFELDER and URETZ, 1966; GEISSLER, 1966, 1967; PATRICK et al., 1964), other investigations indicated the occurrence of dark repair of photodynamic damage in E. coli and Serratia marcescens (RUPP, 1966; BRENDEL and KAPLAN, 1967). The results reported in this paper show that damage inflicted to bacterial or phage DNA by white fluorescent light in the presence of acridine orange or acriflavine is repaired at varying extents by both of the two dark repair systems operating on UV damage. However, the photodynamic lesions are not affected by two phage-controlled dark repair systems existing in T4. © 1968.