Die molekularen Grundlagen der Photoreaktivierung. In: Arber W, Braun W, Cramer F, Haas R, Henle W, Hofschneider PH, Jerne NK, Koldovsky P, Koprowski H, Maaløe O, Rott R, Schweiger H, Sela M, Syruček L, Vogt PK, Wecker E, editors. Current Topics in Microbiology and Immunology. Berlin: Springer Berlin Heidelberg; 1969. pp. 40-68. [DOI: 10.1007/978-3-642-46160-6_3]

Influence of superinfection on the photoreversible phase of UV induced lysogenic bacteria

1. Lysogenic induction by UV light can be reversed by photoreactivation. UV-treated E. coli K12 (lambda)+ uvr+ and uvr cells are sensitive to photoreactivation for a given time after irradiation. This sensitivity suddenly disappears at the end of this time. 2. The photoreversible period of UV induction is more than twice as long in uvr cells as it is in uvr+ cells. 3. The photoreversible period can be reduced by superinfection with lambda c mutants after irradiation. This effect is positively correlated with the multiplicity of superinfection. Such a reduction does not occur when superinfection is carried out with wild-type phages or with heteroimmune derivatives. 4. We concluded that during the photoreversible period of UV induction oligonucleotides are excised or synthesized and gaps are formed during excision repair and post replication repair of UV damage; these might react with E. coli recA protein thereby activating it to induce its own synthesis, to cleave phage repressors and to exert its other SOS functions.

Photoreactivation of bacteriophage phi chi 174

U.V.-irradiated single-stranded DNA-bacteriophage phi chi 174 shows a photoreactivable sector of 0-17. That this sector is relatively small compared with those for the double-stranded DNA-phages T2 and T6 (about 0-5) does not necessarily seem to be due to the pyrimidine dimers in single-stranded DNA being intrinsically a poorer substrate for the photoreactivating enzyme. This follows from the observation that intracellularly irradiated single-stranded phi chi 174 DNA also shows a photoreactivable sector of 0-4 to 0-5. The same value is obtained for intracellularly irradiated double-stranded phi chi 174 DNA. Photoreactivation of intracellularly irradiated single-stranded phi chi 174 DNA is not constant with U.V. dose for the lower dose ranged. Possible explanations for this are discussed.