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PubMed1997

Phylogenetic diversity of the deinococci as determined by 16S ribosomal DNA sequence comparison.

16S ribosomal DNA (rDNA) sequences were determined for the five species of the genus Deinococcus (Deinococcus erythromyxa, Deinococcus proteolyticus, Deinococcus radiodurans, Deinococcus radiophilus, and Deinococcus radiopugnans) and the single species of the genus. Deinobacter (Deinobacter grandis). With the exception of Deinococcus erythromyxa, the deinococci form a coherent phylogenetic cluster which is related to the Thermus-Meiothermus lineage. An analysis of the 16S rDNA sequence of Deinococcus erythromyxa revealed that this organism is an actinomycete and a member of the genus Kocuria. Deinobacter grandis falls within the radiation of the genus Deinococcus and phylogenetically can be considered a member of this genus. The results of the phylogenetic analyses are consistent with chemotaxonomic data. On the basis of our data, Deinobacter grandis is transferred to the genus Deinococcus as Deinococcus grandis comb. nov., the description of the genus Deinococcus is emended accordingly, and Deinococcus erythromyxa is transferred to the genus Kocuria as Kocuria erythromyxa comb. nov. The description of the family Deinococcaceae is emended to include organisms with rod-shaped cells, and a set of 16S rDNA signature nucleotides is designated for this group. On the basis of the distinct phylogenetic position of the Deinococcus lineage and a set of 16S rDNA signature nucleotides, the order Deinococcales ord. nov. is described.

DNA, Bacterial↗
PubMed2005

A ring-like nucleoid is not necessary for radioresistance in the Deinococcaceae.

BACKGROUND: Transmission electron microscopy images of Deinococcus radiodurans R1 suggest that the nucleoid of this species exists as a "ring-like" body, and have led to speculation that this structure contributes to the radioresistance of the species. Since extreme radioresistance is characteristic of six other species of Deinococcus, we have attempted to correlate nucleoid morphology and radioresistance by determining whether the genomic DNA of each of these species exhibit similar structures. RESULTS: The nucleoid morphologies of seven recognized species of Deinococcus, the radioresistant bacterium Rubrobacter radiotolerans, and the more radiosensitive deinococcal relative Thermus aquaticus were evaluated using epifluorescence and deconvolution techniques. Although the nucleoids of Deinococcus murrayi, Deinococcus proteolyticus, Deinococcus radiophilus, and Deinococcus grandis have structures similar to D. radiodurans, the majority of nucleoids found in Deinococcus radiopugnans and Deinococcus geothermalis lack any specific organization. The nucleoid of R. radiotolerans consists of multiple highly condensed spheres of DNA scattered throughout the cell. The genomic DNA of Thermus aquaticus is uniformly distributed throughout the cell. CONCLUSION: There is no obvious relationship between the shape of a species' nucleoid and extreme radioresistance. However, the genomes of all extremely radioresistance species examined are highly condensed relative to more radiosensitive species. Whether DNA in this tightly packed configuration contributes to the radioresistance of these bacteria remains unknown, but this common structural feature appears to limit diffusion of fragments generated post-irradiation even in cells incapable of repairing strand breaks.

DNA, Bacterial↗
PubMed2001

Distribution of genes for lysine biosynthesis through the aminoadipate pathway among prokaryotic genomes.

Deinococcus radioduranshas homologous genes to the genes which from the Thermus: thermophilus gene cluster for lysine biosynthesis. Interestingly, those genes are clustered in Thermus, nevertheless they are scattered in Deinococcus. A similar gene cluster has only been found in Pyrococcus However, the phylogenetic analyses indicated that the deduced gene products from Deinococcus were the most closely related to the proteins encoded in the Thermus gene cluster for lysine biosynthesis. Therefore, those genes had not been transferred horizontally between Pyrococcus and Thermus. It is strongly suggested that a common ancestor of Deinococcus and Thermus possessed the genes for lysine biosynthesis through the aminoadipate pathway. These had been clustered through the evolution of Thermus or had been scattered from the gene cluster through the evolution of Deinococcus. In addition, I showed that LysW and its homologues were specialized proteins for the prokaryotic lysine biosynthesis through the aminoadipate pathway.

Amino Acid Sequence↗
PubMed1990

5S rRNA sequences of myxobacteria and radioresistant bacteria and implications for eubacterial evolution.

5S rRNA sequences were determined for the myxobacteria Cystobacter fuscus, Myxococcus coralloides, Sorangium cellulosum, and Nannocystis exedens and for the radioresistant bacteria Deinococcus radiodurans and Deinococcus radiophilus. A dendrogram was constructed by using weighted pairwise grouping based on these and all other previously known eubacterial 5S rRNA sequences, and this dendrogram showed differences as well as similarities compared with results derived from 16S rRNA analyses. In the dendrogram, Deinococcus 5S rRNA sequences clustered with 5S rRNA sequences of the genus Thermus, as suggested by the results of 16S rRNA analyses. However, in contrast to the 16S rRNA results, the Deinococcus-Thermus cluster divided the 5S rRNA sequences of the alpha subdivision of the class Proteobacteria from the 5S rRNA sequences of the beta and gamma subgroups of the Proteobacteria. The myxobacterial 5S rRNA sequence data failed to confirm the existence of a delta subgroup of the class Proteobacteria, which was suggested by the results of 16S rRNA analyses.

Base Composition↗
PubMed2003

Microbial diversity of cryptoendolithic communities from the McMurdo Dry Valleys, Antarctica.

In the McMurdo Dry Valleys of Antarctica, microorganisms colonize the pore spaces of exposed rocks and are thereby protected from the desiccating environmental conditions on the surface. These cryptoendolithic communities have received attention in microscopy and culture-based studies but have not been examined by molecular approaches. We surveyed the microbial biodiversity of selected cryptoendolithic communities by analyzing clone libraries of rRNA genes amplified from environmental DNA. Over 1,100 individual clones from two types of cryptoendolithic communities, cyanobacterium dominated and lichen dominated, were analyzed. Clones fell into 51 relatedness groups (phylotypes) with > or =98% rRNA sequence identity (46 bacterial and 5 eucaryal). No representatives of Archaea were detected. No phylotypes were shared between the two classes of endolithic communities studied. Clone libraries based on both types of communities were dominated by a relatively small number of phylotypes that, because of their relative abundance, presumably represent the main primary producers in these communities. In the lichen-dominated community, three rRNA sequences, from a fungus, a green alga, and a chloroplast, of the types known to be associated with lichens, accounted for over 70% of the clones. This high abundance confirms the dominance of lichens in this community. In contrast, analysis of the supposedly cyanobacterium-dominated community indicated, in addition to cyanobacteria, at least two unsuspected organisms that, because of their abundance, may play important roles in the community. These included a member of the alpha subdivision of the Proteobacteria that potentially is capable of aerobic anoxygenic photosynthesis and a distant relative of Deinococcus that defines, along with other Deinococcus-related sequences from Antarctica, a new clade within the Thermus-Deinococcus bacterial phylogenetic division.

Alphaproteobacteria↗
PubMed1998

Microbial communities of printing paper machines.

The microbial content of printing paper machines, running at a temperature of 45-50 degrees C and at pH 4.5-5, was studied. Bacteria were prevalent colonizers of the machine wet end and the raw materials. A total of 390 strains of aerobic bacteria were isolated and 86% of these were identified to genus and species by biochemical, chemotaxonomic and phylogenetic methods. The most common bacteria found at the machine wet end were Bacillus coagulans and other Bacillus species, Burkholderia cepacia, Ralstonia pickettii, and in pink slimes, accumulating in the wire area and press section, species of Deinococcus, aureobacterium and Brevibacterium. Paper-making chemicals also contained species of Aureobacterium, B. cereus, B. licheniformis, B. sphaericus, Bordetella, Hydrogenophaga, Klebsiella pneumoniae, Pantoea agglomerans, Pseudomonas stutzeri, Staphylococcus and sometimes other enteric bacteria, but these did not colonize the process water. Yeasts and moulds were not present in significant numbers. A total of 131 strains were tested for their potential to degrade paper-making raw materials; 91 strains were found to have degradative activity, mainly species of Burkholderia and Ralstonia, Sphingomonas and Bacillus, and enterobacteria produced enzymes which degraded paper-making chemicals. Stainless steel adhering strains occurred in slimes and wire water and were identified as Burkholderia cepacia, B. coagulans and Deinococcus geothermalis. Coloured slimes were formed on the machine by species of Deinococcus, Acinetobacter and Methylobacterium (pink), Aureobacterium, Pantoea and Ralstonia (yellowish) and Microbulbifer-related strains (brown). The impact of the strains and species found in the printing paper machine community on the technical quality of paper, machine operation, and as a potential biohazard (Hazard Group 2 bacteria), is discussed.

Bacteria↗
PubMed2004

Novel beta-carotene ketolases from non-photosynthetic bacteria for canthaxanthin synthesis.

We reported previously that the Rhodococcus erythropolis strain AN12 synthesizes the monocyclic carotenoids 4-keto gamma-carotene and gamma-carotene. We also identified a novel lycopene beta-monocyclase in this strain. Here we report the identification of the rest of the carotenoid synthesis genes in AN12. Two of these showed apparent homology to putative phytoene dehydrogenases. Analysis of Rhodococcus knockout mutants suggested that one of them ( crtI) encodes a phytoene dehydrogenase, whereas the other ( crtO) encodes a beta-carotene ketolase. Expression of the beta-carotene ketolase gene in an Escherichia coli strain which accumulates beta-carotene resulted in the production of canthaxanthin. In vitro assays using a crude extract of the E. coli strain expressing the crtO gene confirmed its ketolase activity. A crtO homologue (DR0093) from Deinococcus radiodurans R1 was also shown to encode a beta-carotene ketolase, despite its sequence homology to phytoene dehydrogenases. The Rhodococcus and Deinococcus CrtO ketolases both catalyze the symmetric addition of two keto groups to beta-carotene to produce canthaxanthin. Even though this activity is similar to the CrtW-type of ketolase activity, the CrtO ketolases show no significant sequence homology to CrtW-type ketolases. The presence of six conserved regions may be a signature for the CrtO-type of beta-carotene ketolases.

Amino Acid Sequence↗
PubMed2004

Cysteinyl-tRNA(Cys) formation in Methanocaldococcus jannaschii: the mechanism is still unknown.

Most organisms form Cys-tRNA(Cys), an essential component for protein synthesis, through the action of cysteinyl-tRNA synthetase (CysRS). However, the genomes of Methanocaldococcus jannaschii, Methanothermobacter thermautotrophicus, and Methanopyrus kandleri do not contain a recognizable cysS gene encoding CysRS. It was reported that M. jannaschii prolyl-tRNA synthetase (C. Stathopoulos, T. Li, R. Longman, U. C. Vothknecht, H. D. Becker, M. Ibba, and D. Söll, Science 287:479-482, 2000; R. S. Lipman, K. R. Sowers, and Y. M. Hou, Biochemistry 39:7792-7798, 2000) or the M. jannaschii MJ1477 protein (C. Fabrega, M. A. Farrow, B. Mukhopadhyay, V. de Crécy-Lagard, A. R. Ortiz, and P. Schimmel, Nature 411:110-114, 2001) provides the "missing" CysRS activity for in vivo Cys-tRNA(Cys) formation. These conclusions were supported by complementation of temperature-sensitive Escherichia coli cysS(Ts) strain UQ818 with archaeal proS genes (encoding prolyl-tRNA synthetase) or with the Deinococcus radiodurans DR0705 gene, the ortholog of the MJ1477 gene. Here we show that E. coli UQ818 harbors a mutation (V27E) in CysRS; the largest differences compared to the wild-type enzyme are a fourfold increase in the K(m) for cysteine and a ninefold reduction in the k(cat) for ATP. While transformants of E. coli UQ818 with archaeal and bacterial cysS genes grew at a nonpermissive temperature, growth was also supported by elevated intracellular cysteine levels, e.g., by transformation with an E. coli cysE allele (encoding serine acetyltransferase) or by the addition of cysteine to the culture medium. An E. coli cysS deletion strain permitted a stringent complementation test; growth could be supported only by archaeal or bacterial cysS genes and not by archaeal proS genes or the D. radiodurans DR0705 gene. Construction of a D. radiodurans DR0705 deletion strain showed this gene to be dispensable. However, attempts to delete D. radiodurans cysS failed, suggesting that this is an essential Deinococcus gene. These results imply that it is not established that proS or MJ1477 gene products catalyze Cys-tRNA(Cys) synthesis in M. jannaschii. Thus, the mechanism of Cys-tRNA(Cys) formation in M. jannaschii still remains to be discovered.

Amino Acyl-tRNA Synthetases↗
PubMed2006

Molecular microbial diversity of a soil sample and detection of ammonia oxidizers from Cape Evans, Mcmurdo Dry Valley, Antarctica.

The aim of our study was to estimate the uncultured eubacterial diversity of a soil sample collected below a dead seal, Cape Evans, McMurdo, Antarctica by an SSU rDNA gene library approach. Our study by sequencing of clones from SSU rDNA gene library approach revealed high diversity in the soil sample from Antarctica. More than 50% of clones showed homology to Cytophaga-Flavobacterium-Bacteroides group; sequences also belonged to alpha, beta, gamma proteobacteria, Thermus-Deinococcus and high GC gram-positive group; Phylogenetic analysis of the SSU rDNA clones showed the presence of species belonging to Cytophaga spp., Vitellibacter vladivostokensis, Aequorivita lipolytica, Aequorivita crocea, Flavobacterium spp., Flexibacter sp., Subsaxibacter broadyi, Bacteroidetes, Roseobacter sp., Sphingomonas baekryungensis, Nitrosospira sp., Nitrosomonas cryotolerans, Psychrobacter spp., Chromohalobacter sp., Psychrobacter okhotskensis, Psychrobacter fozii, Psychrobacter urativorans, Rubrobacter radiotolerans, Marinobacter sp., Rubrobacteridae, Desulfotomaculum aeronauticum and Deinococcus sp. The presence of ammonia oxidizing bacteria in Antarctica soil was confirmed by the presence of the amoA gene. Phylogenetic analysis revealed grouping of clones with their respective groups.

Ammonia↗
PubMed2005

Distribution of F- and A/V-type ATPases in Thermus scotoductus and other closely related species.

The presence of an A/V-type ATPase in different Thermus species and in the deeper branching species Meiothermus ruber and Deinococcus radiodurans suggests that the presence of the archaeal-type ATPase is a primitive character of the Deinococci that was acquired through horizontal gene transfer (HGT). However, the presence of a bacterial type F-ATPases was reported in two newly identified Thermus species (Thermus scotoductus DSM 8553 and Thermus filiformis DSM 4687). Two different scenarios can explain this finding, either the recent replacement of the ancestral A/V-type ATPase in Thermus scotoductus and Thermus filiformis with a newly acquired F-type ATPase or a long-term persistence of both F and A type ATPase in the Deinococci, which would imply several independent losses of the F-type ATPase in the Deinococci. Using PCR with redundant primers, sequencing and Southern blot analyses, we tried to confirm the presence of an F-type ATPase in the genome of Thermus scotoductus and Thermus filiformis, and determine its phylogenetic affinities. Initial experiments appeared to confirm the presence of an F-type ATPase in Thermus scotoductus that was similar to the F-ATPases found in Bacillus. However, further experiments revealed that the detection of an F-ATPase was due to a culture contamination. For all the Thermus and Deinococcus species surveyed, including Thermus scotoductus, cultures that were free of contamination only contained an A/V-type ATP synthases.

Adenosine Triphosphatases↗
PubMed2001

Survival of microorganisms under the extreme conditions of the Atacama Desert.

Spores of Bacillus subtilis, conidia of Aspergillus niger, versicolor and ochraceus and cells of Deinococcus radiodurans have been exposed in the dark at two locations (at about 23 degrees S and 24 degrees S) in the Atacama Desert for up to 15 months. B. subtilis spores (survival approximately 15%) and A. niger conidia (survival approximately 30%) outlived the other species. The survival of the conidia and spores species was only slightly poorer than that of the corresponding laboratory controls. However, the Deinococcus radiodurans cells did not survive the desert exposure, because they are readily inactivated at relative humidities between 40 and 80% which typically occur during desert nights. Cellular monolayers of the dry spores and conidia have in addition been exposed to the full sun light for up to several hours. The solar fluences causing 63% loss in viability (F37-values) have been determined. These F37-values are compared with those determined at other global locations such as Punta Arenas (53 degrees S), Key Largo (25 degrees N) or Mainz (50 degrees N) during the same season. The solar UVB radiation kills even the most resistant microorganisms within a few hours due to DNA damages. The data are also discussed with respect to possible similarities between the climatic conditions of the recent Atacama Desert and the deserts of early Mars.

Aspergillus↗
PubMed1999

Dust-borne bacteria in animal sheds, schools and children's day care centres.

A total of 316 bacterial strains, including psychrophiles, mesophiles and thermophiles, were isolated and identified from indoor dusts in schools, children's day care centres and animal sheds. Several species which had not previously been reported from indoor environments were found: Sphingomonas, Brevibacterium, Nocardiopsis, Deinococcus and Rhodococcus/Gordona. A new psychrophilic actinomycete genus was also found in animal sheds, representing a new undescribed peptidoglycan type and an unusual whole-cell fatty acid composition. The indoor dusts of animal sheds contained mainly the Gram-negative genera Pseudomonas, Pantoea, Flavobacterium and Xanthomonas early in the indoor feeding season, but changed to a composition dominated by Bacillus, Micrococcus and mesophilic and thermophilic actinomycetes towards the end of the season. The dust contained, and air-borne bacterial flora in schools and day care centres were dominated by, Gram-positive bacilli and actinomycetes, notably Bacillus cereus, Brevibacillus brevis, B. licheniformis, B. subtilis and species of Arthrobacter, Corynebacterium, Rhodococcus/Gordona, Nocardiopsis sp., Deinococcus, Staphylococcus and Micrococcus. Indoor air and dust contained Klebsiella oxytoca, Acinetobacter calcoaceticus, Ac. lwoffi, Bacillus cereus and Nocardiopsis dassonvillei with the status of hazard group II. Indoor dusts of animal sheds contained eight different 3-hydroxy fatty acids, the 2-hydroxy fatty acid 14:0 and two 10-methyl fatty acids, whereas in dusts from schools and day care centres, these were below the detection level (< 3.5 ng mg-1). The 3-and 2-hydroxy fatty acids could be assigned to one or more of the dust-contained cultivable strains, but 10-methyl C16:0 was not present in any of the strains isolated. The dusts from schools and children's day care centres contained 0.2-0.3 ng of endotoxin mg-1 and 0.5-1.4 ng of beta-D-glucan mg-1, whereas the dusts from animal sheds contained more 0.3-41 ng mg-1 and 8-35 ng mg-1, respectively.

Air Microbiology↗
PubMed2002

Transfer RNA-dependent amino acid biosynthesis: an essential route to asparagine formation.

Biochemical experiments and genomic sequence analysis showed that Deinococcus radiodurans and Thermus thermophilus do not possess asparagine synthetase (encoded by asnA or asnB), the enzyme forming asparagine from aspartate. Instead these organisms derive asparagine from asparaginyl-tRNA, which is made from aspartate in the tRNA-dependent transamidation pathway [Becker, H. D. & Kern, D. (1998) Proc. Natl. Acad. Sci. USA 95, 12832-12837; and Curnow, A. W., Tumbula, D. L., Pelaschier, J. T., Min, B. & Söll, D. (1998) Proc. Natl. Acad. Sci. USA 95, 12838-12843]. A genetic knockout disrupting this pathway deprives D. radiodurans of the ability to synthesize asparagine and confers asparagine auxotrophy. The organism's capacity to make asparagine could be restored by transformation with Escherichia coli asnB. This result demonstrates that in Deinococcus, the only route to asparagine is via asparaginyl-tRNA. Analysis of the completed genomes of many bacteria reveal that, barring the existence of an unknown pathway of asparagine biosynthesis, a wide spectrum of bacteria rely on the tRNA-dependent transamidation pathway as the sole route to asparagine.

Amino Acids↗
PubMed2003

Colored moderately thermophilic bacteria in paper-machine biofilms.

Biofilms cause several problems in papermaking. This report describes a microbiological survey of colored biofilms in six paper and board machines, including two case studies of outbreaks of colored slimes in which the causative bacteria were found. A total of 95 pink-, red-, orange- or yellow-pigmented strains were isolated. Nearly all (99%) of the strains grew at 52 degrees C, 72% grew at 56 degrees C, but only 30% grew at 28 degrees C, indicating that most of the strains were moderately thermophilic. Biofilm formation potential and biocide susceptibility of the strains were analyzed with a microtiter plate assay. In the presence of 5 ppm of methylene bisthiocyanate or 2,2-dibromo-3-nitrilopropionamide in paper-machine water, 55 strains formed biofims. Moreover, 39 strains increased biofilm production by 5-753% in the presence of biocide, suggesting that biocide concentrations inhibitory to planktonic but not to surface-attached cells may actually promote biofouling. The cells may have inactivated a portion of the biocides, as the cell density in this assay was high, corresponding to the highest cell densities occurring in the circulating waters. Four groups of colored bacteria that were isolated from several mills were identified. Pink-pigmented Deinococcus geothermalis and red-pigmented Meiothermus silvanus occurred as common primary biofilm-formers in paper machines. This report is the first description of the involvement of Meiothermus species in red-slime formation in the paper industry. The third group of bacteria (putative new species related to Roseomonas) contained strains that were not biofilm formers, but which were commonly found in slimes of neutral or alkaline machines. The fourth group contained red-pigmented biofilm-forming strains representing a novel genus of alpha- Proteobacteria related to Rhodobacter. Many colored paper-machine bacteria are species previously known from microbial mats of hot springs. Some characteristics of the bacterial groups are described here in order to facilitate their recognition in future cases of colored-slime outbreaks in the paper industry.

Biofilms↗
PubMed2005

Identification of a novel trifunctional homoisocitrate dehydrogenase and modulation of the broad substrate specificity through site-directed mutagenesis.

A gene encoding homoisocitrate dehydrogenase (HICDH) of Deinococcus radiodurans was cloned, sequenced, and overexpressed in Escherichia coli. The amino acid sequence was 63% identical to HICDH from Thermus thermophilus (Tth-HICDH). Similar to Tth-HICDH, purified, recombinant Dra-HICDH was a tetramer, required K+ and Mn2+ for activity, and used NAD+ as a coenzyme. However, unlike Tth-HICDH, which has a 20-fold preference for isocitrate over homoisocitrate, Dra-HICDH preferred homoisocitrate to isocitrate by 1.5-fold. Moreover, it catalyzed the oxidation of 3-isopropylmalate, albeit at approximately 0.1% the rate seen with homoisocitrate and isocitrate. Saturation mutagenesis of Dra-HICDH Arg87 was next performed because an orthologous Arg85 to valine mutation in Tth-HICDH results in loss of activity toward isocitrate, but in retention of activity toward homoisocitrate. Unexpectedly, the Arg85Val variant became able to catalyze the oxidation of 3-isopropylmalate. Screening of the saturation mutagenesis library identified two variants, Arg87Val and Arg87Thr, that were able to catalyze the oxidation of homoisocitrate, but not isocitrate or 3-isopropylmalate. Deletion of Dra-HICDH Ala80, a residue missing from Tth-HICDH and predicted to reside at the entrance of alpha-helix Arg87, resulted in alterations in substrate specificity that rendered Dra-HICDH similar to Tth-HICDH; i.e., a 4-fold preference for isocitrate over homoisocitrate and inability to catalyze the oxidation of 3-isopropylmalate. Seemingly minor changes in primary sequence result in changes in substrate specificity of beta-decarboxylating dehydrogenases.

Alcohol Oxidoreductases↗
PubMed2006

Substrate specificity analysis and inhibitor design of homoisocitrate dehydrogenase.

Homoisocitrate dehydrogenase is involved in the alpha-aminoadipate pathway of biosynthesis of l-lysine in fungi, yeast, some prokaryotic bacteria, and archaea. This enzyme catalyzes the oxidative decarboxylation of (2R,3S)-homoisocitrate into 2-oxoadipate using NAD(+) as a coenzyme. Substrate specificity of two homoisocitrate dehydrogenases derived from Deinococcus radiodurans and Saccharomyces cerevisiae was analyzed using a series of synthetic substrate analogs, which indicated a relatively broad substrate specificity of these enzymes. Based on the substrate specificity, 3-hydroxyalkylidene- and 3-carboxyalkylidenemalate derivatives were designed as a specific inhibitor for homoisocitrate dehydrogenase. The synthetic inhibitors showed a moderate competitive inhibitory activity and (R,Z)-3-carboxypropylidenemalate was the most inhibitory among the synthesized inhibitors. Therefore, homoisocitrate dehydrogenase appeared to recognize preferentially an extended conformation of homoisocitrate.

Alcohol Oxidoreductases↗
PubMed2007

Radiation resistance: resurrection by recombination.

Adaptation to extreme desiccation has conferred extraordinary radiation resistance on the bacterium Deinococcus radiodurans. How this organism is able to reconstruct a genome shattered by gamma rays has now been revealed.

DNA, Bacterial↗
PubMed2004

Pyrroloquinoline-quinone: a reactive oxygen species scavenger in bacteria.

Transgenic Escherichia coli expressing pyrroloquinoline-quinone (PQQ) synthase gene from Deinococcus radiodurans showed superior survival during Rose Bengal induced oxidative stress. Such cells showed significantly low levels of protein carbonylation as compared to non-transgenic control. In vitro, PQQ reacted with reactive oxygen species with rate constants comparable to other well known antioxidants, producing non-reactive molecular products. PQQ also protected plasmid DNA and proteins from the oxidative damage caused by gamma-irradiation in solution. The data suggest that radioprotective/oxidative stress protective ability of PQQ in bacteria may be consequent to scavenging of reactive oxygen species per se and induction of other free radical scavenging mechanism.

Animals↗