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At least 271 records · Page 15Linked to original sources
PubMed2004

Analysis of Deinococcus radiodurans's transcriptional response to ionizing radiation and desiccation reveals novel proteins that contribute to extreme radioresistance.

During the first hour after a sublethal dose of ionizing radiation, 72 genes were upregulated threefold or higher in D. radiodurans R1. Thirty-three of these loci were also among a set of 73 genes expressed in R1 cultures recovering from desiccation. The five transcripts most highly induced in response to each stress are the same and encode proteins of unknown function. The genes (ddrA, ddrB, ddrC, ddrD, and pprA) corresponding to these transcripts were deleted, both alone and in all possible two-way combinations. Characterization of the mutant strains defines three epistasis groups that reflect different cellular responses to ionizing radiation-induced damage. The ddrA and ddrB gene products have complementary activities and inactivating both loci generates a strain that is more sensitive to ionizing radiation than strains in which either single gene has been deleted. These proteins appear to mediate efficient RecA-independent processes connected to ionizing radiation resistance. The pprA gene product is not necessary for homologous recombination during natural transformation, but nevertheless may participate in a RecA-dependent process during recovery from radiation damage. These characterizations clearly demonstrate that novel mechanisms significantly contribute to the ionizing radiation resistance in D. radiodurans.

Deinococcus↗
PubMed1999

[The effect of N+ implantation on SOD activity of Deinococcus radiodurans and induction of Mn-SOD].

The induction of Mn-SOD and effect of N+ of 20 keV implantation on SOD activity of D. radiodurans were investigated. The results were as follows: (1) SOD activity of D. radiodurans had a little change when implantation dose was less than 8 x 10(14) N+/cm2, and increased gradually from 8 x 10(14) to 60 x 10(14) N+/cm2, and then decreased rapidly; (2) the test of adding H2O2 and CHCl3-CH3CH2OH which could inhibit different types of SOD showed that most SOD activity of D. radiodurans was constituted by Fe-SOD in general physiology and less then 8 x 10(14)N+/cm2 dose, and higher implantation dose induced increase of Mn-SOD activity.

Deinococcus↗
PubMed2002

Bacteriophage Mu genome sequence: analysis and comparison with Mu-like prophages in Haemophilus, Neisseria and Deinococcus.

We report the complete 36,717 bp genome sequence of bacteriophage Mu and provide an analysis of the sequence, both with regard to the new genes and other genetic features revealed by the sequence itself and by a comparison to eight complete or nearly complete Mu-like prophage genomes found in the genomes of a diverse group of bacteria. The comparative studies confirm that members of the Mu-related family of phage genomes are genetically mosaic with respect to each other, as seen in other groups of phages such as the phage lambda-related group of phages of enteric hosts and the phage L5-related group of mycobacteriophages. Mu also possesses segments of similarity, typically gene-sized, to genomes of otherwise non-Mu-like phages. The comparisons show that some well-known features of the Mu genome, including the invertible segment encoding tail fiber sequences, are not present in most members of the Mu genome sequence family examined here, suggesting that their presence may be relatively volatile over evolutionary time. The head and tail-encoding structural genes of Mu have only very weak similarity to the corresponding genes of other well-studied phage types. However, these weak similarities, and in some cases biochemical data, can be used to establish tentative functional assignments for 12 of the head and tail genes. These assignments are strongly supported by the fact that the order of gene functions assigned in this way conforms to the strongly conserved order of head and tail genes established in a wide variety of other phages. We show that the Mu head assembly scaffolding protein is encoded by a gene nested in-frame within the C-terminal half of another gene that encodes the putative head maturation protease. This is reminiscent of the arrangement established for phage lambda.

Amino Acid Sequence↗
PubMed1983

Mutation induction by cross-links in DNA of Deinococcus radiodurans.

Reversion of adenine auxotrophic strains of D. radiodurans by cross-links in DNA was studied. Mutation was induced in a wild-type but not in a mitomycin C sensitive mutant after irradiation with near UV (approximately 365nm) in the presence of 4,5',8-trimethylpsoralen (TMP). To get information on implication of cross-links in the observed mutation, cells containing monoadducts in DNA were exposed to near UV in the absence of TMP. The mutation frequency of the wild-type increased with increasing the cross-links in DNA. These results suggest that structural defects after removal of cross-links in DNA induce mutation in D. radiodurans.

Chemical Phenomena↗
PubMed1986

Sensitivity of Deinococcus radiodurans to near-ultraviolet radiation.

Although Dienococcus radiodurans is notoriously resistant to far-ultraviolet radiation (FUV; 254 nm), it is highly sensitive to near-ultraviolet radiation (NUV; 300-400 nm), thus demonstrating that the mechanisms of damage (and/or recovery) by the two types of irradiation are different. This observed difference between FUV and NUV effects in D. radiodurans agrees with previous studies with Escherichia coli. Near-ultraviolet radiation produces DNA damage which is presumed to be single-strand breaks (SSB) in the DNA of D. radiodurans. Unique lesions, such as DNA-protein crosslinks could not be demonstrated in this study. Cells that were pre-irradiated with a small dose of NUV were subsequently protected against inactivating doses of NUV. The data presented are consistent with induced DNA repair following NUV damage in D. radiodurans; this is in contrast to FUV damage where DNA repair is constitutive but not induced.

DNA Repair↗
PubMedDate not supplied

Lipid composition, lipid fluidity and radioresistance of Deinococcus radiodurans and two mutant strains.

The lipid composition of D. radiodurans strain R1 and of two mutant strains has been studied in relation to membrane fluidity and sensitivity to X-ray radiation. No significant difference in the unsaturation degree of fatty acids was found between parental and mutant strains. An important decrease of carbohydrate-containing lipids was observed in the radiosensitive mutant strain. We also observed a higher fluidity in both mutant strains than in the parental one. Modification of membrane lipid fluidity by growing the parental strain at 39 degrees C did not lead to modified radioresistance. These results suggest that a particular chemical composition of the membrane leading to a special lipid phase may be an important parameter in controlling radiosensitivity.

Carbohydrates↗
PubMed2000

Deinococcus radiodurans CatB Gene Cloning and Expression in Escherichia coli.

A 1 611 bp length complete coding sequence of the catalase (Cat) was obtained through bioimformatical analysis of the database of D.radiodurans genome, and then was amplified from D. radiodurans genomic DNA by polymerase chain reaction. The amplified gene was cloned into pKK223-3 vector and transformed into E.coli UM2, a Cat-deficient mutant. Staining of non-denaturing polyacrylamide gels for Cat activity demonstrated that pKK223-3 insert encoded a Cat that co-migrated with the CatB found in D.radiodurans cell lysates. Expression of CatB gene from D.radiodurans in E.coli UM2 restored the resistance to H(2)O(2) at low concentrations.

Journal Article↗