Transformation in Micrococcus radiodurans: Measurement of Various Parameters and Evidence for Multiple, Independently Segregating Genomes per Cell

Tirgari, S; Moseley, Bevan

doi:10.1099/00221287-119-2-287

Cited by 30 publications

(29 citation statements)

References 24 publications

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“…This study began with the intent of identifying irrE. To accomplish this task, we took advantage of the D. radiodurans genome sequence and the efficiency of natural transformation in this species (28). A cosmid library generated from D. radiodurans R1 genomic DNA was transformed into competent IRS24 cultures and screened for clones capable of restoring ionizing radiation resistance to the strain.…”

Section: Discussionmentioning

confidence: 99%

The IrrE Protein of Deinococcus radiodurans R1 Is a Novel Regulator of recA Expression

et al. 2002

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IRS24 is a DNA damage-sensitive strain of Deinococcus radiodurans strain 302 carrying a mutation in an uncharacterized locus designated irrE. Five overlapping cosmids capable of restoring ionizing radiation resistance to IRS24 were isolated from a genomic library. The ends of each cloned insert were sequenced, and these sequences were used to localize irrE to a 970-bp region on chromosome I of D. radiodurans R1. The irrE gene corresponds to coding sequence DR0167 in the R1 genome. The irrE gene encodes a 35,000-Da protein that has no similarity to any previously characterized peptide. The irrE locus of R1 was also inactivated by transposon mutagenesis, and this strain was sensitive to ionizing radiation, UV light, and mitomycin C. Preliminary findings indicate that IrrE is a novel regulatory protein that stimulates transcription of the recA gene following exposure to ionizing radiation.The bacterium Deinococcus radiodurans is known for its tolerance to many DNA-damaging agents, but it is its unusually high resistance to the lethal and mutagenic effects of ionizing radiation that distinguishes this species from other organisms (3,5,17,20,24). Exponential-phase cultures of D. radiodurans R1 survive exposure to gamma radiation at doses as high as 5,000 Gy without loss of viability or evidence of DNA damageinduced mutation (23). A 5,000-Gy dose of gamma radiation should introduce not less than 130 DNA double-strand breaks into each copy of the D. radiodurans R1 genome present within the irradiated cell (6), and direct measurements of ionizing radiation-induced DNA double-strand breaks indicate that D. radiodurans suffers this level of DNA damage (13, 18). The mechanisms responsible for the DNA damage resistance of this species remain unknown.As part of an effort to obtain a better understanding of the ionizing radiation resistance of D. radiodurans R1, this laboratory isolated 41 ionizing radiation-sensitive (IRS1 to -41) derivatives of D. radiodurans 302 (uvrA1) (29). Strain 302 is approximately 50 times more mutable than the wild-type R1 strain following N-methyl-

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Section: Discussionmentioning

confidence: 99%

The IrrE Protein of Deinococcus radiodurans R1 Is a Novel Regulator of recA Expression

et al. 2002

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“…Its cells are competent throughout the exponential growth stage. The frequency of transformants falls only during stationary phase (448,620), whereas other bacteria have maximal competence just before they enter stationary phase (509). CaCl 2 (30 mM) increases the frequency of transformation 40 times, with marker-specific efficiencies ranging from 0.01 to 3% (620).…”

Section: Genetics Of D Radioduransmentioning

confidence: 99%

“…The frequency of transformants falls only during stationary phase (448,620), whereas other bacteria have maximal competence just before they enter stationary phase (509). CaCl 2 (30 mM) increases the frequency of transformation 40 times, with marker-specific efficiencies ranging from 0.01 to 3% (620). A family of 13 proteins that are homologous to the putative nuclease inhibitor DinB in B. subtilis (50,232,380) may enhance the transformation proficiency of D. radiodurans.…”

Section: Genetics Of D Radioduransmentioning

confidence: 99%

Oxidative Stress Resistance inDeinococcus radiodurans

Slade

Radman

2011

Microbiol Mol Biol Rev

648

639

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SUMMARY Deinococcus radiodurans is a robust bacterium best known for its capacity to repair massive DNA damage efficiently and accurately. It is extremely resistant to many DNA-damaging agents, including ionizing radiation and UV radiation (100 to 295 nm), desiccation, and mitomycin C, which induce oxidative damage not only to DNA but also to all cellular macromolecules via the production of reactive oxygen species. The extreme resilience of D. radiodurans to oxidative stress is imparted synergistically by an efficient protection of proteins against oxidative stress and an efficient DNA repair mechanism, enhanced by functional redundancies in both systems. D. radiodurans assets for the prevention of and recovery from oxidative stress are extensively reviewed here. Radiation- and desiccation-resistant bacteria such as D. radiodurans have substantially lower protein oxidation levels than do sensitive bacteria but have similar yields of DNA double-strand breaks. These findings challenge the concept of DNA as the primary target of radiation toxicity while advancing protein damage, and the protection of proteins against oxidative damage, as a new paradigm of radiation toxicity and survival. The protection of DNA repair and other proteins against oxidative damage is imparted by enzymatic and nonenzymatic antioxidant defense systems dominated by divalent manganese complexes. Given that oxidative stress caused by the accumulation of reactive oxygen species is associated with aging and cancer, a comprehensive outlook on D. radiodurans strategies of combating oxidative stress may open new avenues for antiaging and anticancer treatments. The study of the antioxidation protection in D. radiodurans is therefore of considerable potential interest for medicine and public health.

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“…1A). Since the Rif' point marker used is the most efficiently transformed marker discovered to date (21), the equally high level of efficiency of transformation to MMC resistance by using either wt or strain 112 genomic DNA suggests that the rec30 defect is due to a single mutation and, furthermore, that the rec30 mutation is not closely linked with the 112 defect. Two rec30 MMC-resistant isolates, one transformed by wt genomic DNA (30/wt) and one transformed by strain 112 genomic DNA (30/1), were found to be wt in all respects, including efficient natural transformation (Fig.…”

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confidence: 99%

“…The most studied of these species, Deinococcus radiodurans, was found to be naturally transformable by Moseley and coworkers, who showed that this organism is always competent during the exponential phase without manipulation and provided evidence, by using unlinked markers, for a minimum of four independently segregating genomes per cell (13,21). The latter observation is consistent with evidence based on renaturation kinetics (5) and pulsed-field gel electrophoresis (4) that D. radiodurans contains 4 chromosomes per nucleoid in the plateau phase and 8 to 10 chromosomes during exponential growth (9).…”

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confidence: 99%

Heterozygosity and instability of amplified chromosomal insertions in the radioresistant bacterium Deinococcus radiodurans

et al. 1991

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Natural transformation, duplication insertion, and plasmid transformation in Deinococcus radiodurans, a bacterium that contains 4 to 10 chromosomes per cell, were studied. Duplication insertions were often heterozygous, with some chromosomes containing highly amplified insertions and others containing no insertions. Large amplified regions were apparently deleted by intrachromosomal recombination, generating as by-products extrachromosomal circles consisting of multiple tandem repeats of the (Fig. 1A). Strain rec30, which is unusually sensitive to MMC (Fig. 2), was transformed to MMC resistance by genomic DNA from wt (Fig.

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Transformation in Micrococcus radiodurans: Measurement of Various Parameters and Evidence for Multiple, Independently Segregating Genomes per Cell

Cited by 30 publications

References 24 publications

The IrrE Protein of Deinococcus radiodurans R1 Is a Novel Regulator of recA Expression

The IrrE Protein of Deinococcus radiodurans R1 Is a Novel Regulator of recA Expression

Oxidative Stress Resistance inDeinococcus radiodurans

Heterozygosity and instability of amplified chromosomal insertions in the radioresistant bacterium Deinococcus radiodurans

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