ABSTRACT
The role of the HCR system in the repair of prelethal lesions induced by UV-light, gamma-rays and alkylating agents was studied in the Bacillus subtilis SPP1 phage, its thermosensitive mutants (N3, N73 and ts1) and corresponding infectious DNA. The survival of phages and their transfecting DNA after treatment with UV light is substantially higher in hcr+ cells than in hcr cells, the differences being more striking in intact phages than in their transfecting DNA's. Repair inhibitors reduce the survival in hcr+ cells: caffeine lowers the survival of UV-irradiated phage SPP1 in exponentially growing hcr+ cells but has no effect on its survival in competent hcr+ cells; acriflavin and ethidium bromide decrease the survival of UV-irradiated SPP1 phage in both exponentially growing and competent hcr+ cells to the level of survival observed in hcr cells; moreover, ethidium bromide lowers the number of infective centres in hcr+ cells of UV-irradiated DNA of the SPP1 phage. Repair inhibitors do not lower the survival of UV-irradiated phages or their DNA in hcr cells. The repair mechanism under study repairs also lesions induced by polyfunctional alkylating agents in transfecting DNA's of B. subtilis phages but is not functional with lesions induced by these agents in free phages and lesions caused in phages and their DNA by ethyl methanesulphonate or gamma-rays.
Subject(s)
Bacillus subtilis/metabolism , Bacteriophages/metabolism , DNA Repair , DNA, Viral/biosynthesis , Alkylating Agents/pharmacology , Bacteriophages/drug effects , Bacteriophages/radiation effects , DNA, Viral/radiation effects , Gamma Rays , Mutation , Temperature , Transfection , Ultraviolet RaysABSTRACT
Inactivation of seven strains derived from Escherichia coli B differing in their capacity to repair damage to their DNA (exc, pol, rec) after irradiation with far (254 nm) and middle and near (300 to 380 and 320--400 nm) UV light was investigated. The same bacterial strains were also used as hosts for the UV-irradiated phage T7. The damage induced in bacteria and the phage by the near UV radiation was repaired only to a lesser extent by the investigated repair mechanisms or was not repaired at all.
Subject(s)
DNA Repair , DNA, Bacterial/radiation effects , Ultraviolet Rays , DNA, Bacterial/biosynthesis , DNA, Viral/biosynthesis , DNA, Viral/radiation effects , Darkness , Escherichia coli/metabolism , Escherichia coli/radiation effects , T-Phages/metabolism , T-Phages/radiation effectsABSTRACT
A comparison has been made of sensitivity to far (254 nm), middle (300--315 nm) and near (315--400 nm) UV radiation of 12 strains of E. coli and 2 strains of B. subtilis differing in DNA dark repair (DR) capability. The mechanisms controlled by uvrA, uvrB, polA, recA, lon, and lexA genes are very effective in cells, irradiated by far and middle UV, but by 15--70% less effective in those irradiated by near UV. As the unirradiated bacteria poorly repair the near UV damaged phages (T7, lambda, SPPI), the low bacterial DR level after UV irradiation seems to be due to the unrepairable photoproduct formation in DNA.
Subject(s)
Bacillus subtilis/radiation effects , Bacteriophage lambda/radiation effects , Bacteriophages/radiation effects , DNA Repair/radiation effects , Dark Adaptation/radiation effects , Escherichia coli/radiation effects , T-Phages/radiation effects , Ultraviolet Rays , DNA, Bacterial/radiation effects , DNA, Viral/radiation effects , Genes/radiation effects , MutationABSTRACT
Photoreactivation (PR) was measured after inactivation by far (254 nm), middle (300-315 nm) and near (315-400 nm) UV radiation of Paramecium caudatum and 8 strains of Escherichia coli differing in PR and dark repair capability. PR volume was high and practically the same after irradiation by far and middle UV, but PR was not observed in near UV-inactivated cells of all the strains. It is proposed that pyrimidine dimers are not significant in near UV lethal lesions in cells, as near UV-irradiated phages (T7 and lambdacI 857) are not photoreactivated in undamaged host bacterial cells.
Subject(s)
Coliphages/radiation effects , Light , Paramecium/radiation effects , Ultraviolet Rays , Cell Division/radiation effects , Clone Cells/radiation effects , Radiation ToleranceABSTRACT
Inactivation of bacterial strains derived from E. coli B, which differ in the DNA-repair capacity (exc-, pol- and rec-) was investigated after far and near UV irradiation. The same strains were also used as hosts for UV-irradiated phage T7. The injuries caused in bacteria and phages by radiation with longer wavelengths were reparable with greater difficulty and only to a lesser extent by the investigated repair mechanisms. We suppose that near UV affects cell proteins and that, as a result of this damage, the DNA-repair systems may be inhibited.
Subject(s)
DNA Repair , Escherichia coli/radiation effects , T-Phages/radiation effects , Ultraviolet Rays , DNA Repair/radiation effects , DNA, Bacterial/biosynthesis , DNA, Viral/biosynthesis , Escherichia coli/metabolism , Escherichia coli/physiology , Light , T-Phages/metabolism , T-Phages/physiologyABSTRACT
A total of 30 ts mutants of Bacillus subtilis bacteriophage SPP1 were isolated and subjected to complementation test. On the basis of this test 21 mutants were classified into 4 functional groups; the classification of the remaining 9 mutants was unclear. The frequency of recombination by mutual crossing was determined in representatives of individual groups; this made it possible to place these mutants on a linear map comprising a total length of 7.62 recombination units.
