Isolation and Properties of Strains of Micrococcus (Deinococcus) radiodurans Unable to Excise Ultraviolet Light-induced Pyrimidine Dimers from DNA: Evidence for Two Excision Pathways

Abstract

A mutant of Deinococcus (formerly Micrococcus) radiodurans (strain 302, mutant in mtcA) sensitive to both the lethal effect of mitomycin C and the mutagenic effect of simple alkylating agents, but having wild-type resistance to UV light, was treated with the mutagen N-methyl-N'-nitro-N-nitrosoguanidine in an attempt to isolate strains deficient in the ability to excise UV-induced pyrimidine dimers. Three strains were isolated that were UV-sensitive, but had wild-type resistance to the lethal effect of methyl methanesulphonate and all were shown to be unable to excise pyrimidine dimers. The three strains UVS9, UVS25 and UVS78 had, in addition to the mutation in mtcA, mutations in loci designated uvsC, uvsD and uvsE, respectively. When the mutant mtcA gene was replaced by its wild-type allele in all three strains they became UV- and mitomycin C-resistant. On incubating the double mutants UVS9, UVS25 and UVS78 with wild-type DNA about 50% of the transformants selected for UV resistance were mitomycin C-sensitive and about 50% resistant depending on whether the mutant mtcA or the uvsC, D or E genes had been replaced by their wild-type alleles. Although strains mutant singly in uvsC, D or E were UV-resistant the rates of excision of pyrimidine dimers differed between them and was slower in all of them than in the wild-type and strain 302. The results indicate that wild-type D. radiodurans possesses two pathways for the excision of pyrimidine dimers and that mutational blocks in both must exist for the excisionless phenotype to be expressed.

Transcriptome dynamics of Deinococcus radiodurans recovering from ionizing radiation

“…After an exposure dose of 15 kGy, Ϸ150 DSBs are inflicted randomly over DEIRA's four circular genomic partitions (14), followed by extensive exonucleolytic DNA degradation (35). In acutely irradiated cells, this causes a substantial lowering of the copy number of the more heavily damaged, larger genomic partitions compared with smaller ones in the mid and late phases of recovery (12).…”

Rubrobacter taiwanensis sp. nov., a novel thermophilic, radiation-resistant species isolated from hot springs

“…2). Radiation-resistant bacterial strains including D. radiodurans, D. geothermalis, D. murrayi, R. radiotolerans and R. xylanophilus have exhibited variable radiation resistance in previous studies (Moseley, 1967;Moseley & Mattingly, 1971;Moseley & Evans, 1983;Ferreira et al, 1997;Suzuki et al, 1988;Yoshinaka et al, 1973;Carreto et al, 1996). Of these radiation-resistant bacteria, the thermophilic species D. murrayi exhibited stronger resistance to gamma-radiation (shoulder doses, 7?3 kGy) than did the well-known species D. radiodurans (shoulder doses, 5?0 kGy) and would be the most radiation-resistant bacterium currently known.…”

Space as a Tool for Astrobiology: Review and Recommendations for Experimentations in Earth Orbit and Beyond

“…We will also investigate DNA damage under LEO environment using D. radiodurans DNA repair-deficient mutant strains. In addition to the wild type, mutant strains of D. radiodurans have been exposed: D. radiodurans KH311 (carrying a mutation in the pprA gene: Kitayama et al 1983;Narumi et al 2004), D. radiodurans UVS78 (carrying a mutation in the uvrA and the uvdE genes (Moseley and Evans 1983)) and D. radiodurans rec30 (carrying a mutation in the recA gene: Moseley and Copland 1975). After the exposure experiment of dried deinoccocal cells, the Tanpopo team will investigate DNA damage such as DNA double-and single-strand breaks by survivability test, pulsed-field gel electrophoresis, and by quantitative Polymerase Chain Reaction (PCR).…”