Experimental evolution of extremophile resistance to ionizing radiation.

A growing number of known species possess a remarkable characteristic - extreme resistance to the effects of ionizing radiation (IR). This review examines our current understanding of how organisms can adapt to and survive exposure to IR, one of the most toxic stressors known. The study of natural extremophiles such as Deinococcus radiodurans has revealed much. However, the evolution of Deinococcus was not driven by IR. Another approach, pioneered by Evelyn Witkin in 1946, is to utilize experimental evolution. Contributions to the IR-resistance phenotype affect multiple aspects of cell physiology, including DNA repair, removal of reactive oxygen species, the structure and packaging of DNA and the cell itself, and repair of iron-sulfur centers. Based on progress to date, we overview the diversity of mechanisms that can contribute to biological IR resistance arising as a result of either natural or experimental evolution.

Single-molecule observation of ATP-independent SSB displacement by RecO in Deinococcus radiodurans.

Deinococcus radiodurans (DR) survives in the presence of hundreds of double-stranded DNA (dsDNA) breaks by efficiently repairing such breaks. RecO, a protein that is essential for the extreme radioresistance of DR, is one of the major recombination mediator proteins in the RecA-loading process in the RecFOR pathway. However, how RecO participates in the RecA-loading process is still unclear. In this work, we investigated the function of drRecO using single-molecule techniques. We found that drRecO competes with the ssDNA-binding protein (drSSB) for binding to the freely exposed ssDNA, and efficiently displaces drSSB from ssDNA without consuming ATP. drRecO replaces drSSB and dissociates it completely from ssDNA even though drSSB binds to ssDNA approximately 300 times more strongly than drRecO does. We suggest that drRecO facilitates the loading of RecA onto drSSB-coated ssDNA by utilizing a small drSSB-free space on ssDNA that is generated by the fast diffusion of drSSB on ssDNA.

Computational search for UV radiation resistance strategies in Deinococcus swuensis isolated from Paramo ecosystems.

Ultraviolet radiation (UVR) is widely known as deleterious for many organisms since it can cause damage to biomolecules either directly or indirectly via the formation of reactive oxygen species. The goal of this study was to analyze the capacity of high-mountain Espeletia hartwegiana plant phyllosphere microorganisms to survive UVR and to identify genes related to resistance strategies. A strain of Deinococcus swuensis showed a high survival rate of up to 60% after UVR treatment at 800J/m2 and was used for differential expression analysis using RNA-seq after exposing cells to 400J/m2 of UVR (with >95% survival rate). Differentially expressed genes were identified using the R-Bioconductor package NOISeq and compared with other reported resistance strategies reported for this genus. Genes identified as being overexpressed included transcriptional regulators and genes involved in protection against damage by UVR. Non-coding (nc)RNAs were also differentially expressed, some of which have not been previously implicated. This study characterized the immediate radiation response of D. swuensis and indicates the involvement of ncRNAs in the adaptation to extreme environmental conditions.

Glycine Betaine Effect on Dormancy in Deinococcus sp. UDEC-P1 and Psychrobacter sp. UDEC-A5 Exposed to Hyperosmotic Stress.

Bacteria under stress increase the proportion of dormant cells to ensure their survival. Cold and osmotic stress are similar, because in both the availability of water is reduced. Glycine betaine (GB) is one of the most common osmoprotectants in bacteria and possesses cryoprotectant properties. Our aim was to determine whether GB modifies the proportion of dormant Deinococcus sp. UDEC-P1 and Psychrobacter sp. UDEC-A5 cells exposed to osmotic stress. Both bacterial strains were incubated in the presence of up to 1 M NaCl with or without GB. Active and dormant cells were evaluated by both spectrophotometric and flow cytometry analysis. Without GB, Deinococcus sp. UDEC-P1 grew in the presence of 0.05 M NaCl, but with 5 mM GB grew at 0.1 M NaCl. Psychrobacter sp. UDEC-A5 grew in the presence of up to 0.25 M NaCl, but with 5 mM GB grew at 0.5 M NaCl. Under osmotic stress, the proportion of dormant cells of Deinococcus sp. UDEC-P1 and Psychrobacter sp. UDEC-A5 increased significantly (about eightfold and fivefold, respectively). The addition of GB (5 mM) exerted a different effect on the two strains, since it avoided the entrance into the dormancy of Psychrobacter sp. UDEC-A5 cells, but not of Deinococcus sp. UDEC-P1 cells. Our results suggest that the effect of GB on bacterial metabolism is strain dependent. For bacteria in which GB avoids dormancy, such as Psychrobacter sp. UDEC-A5, it could be a "double-edged sword" by reducing the "seed bank" available to recover the active population when favorable conditions return.

Tolerances of Deinococcus geothermalis Biofilms and Planktonic Cells Exposed to Space and Simulated Martian Conditions in Low Earth Orbit for Almost Two Years.

Fossilized biofilms represent one of the oldest known confirmations of life on the Earth. The success of microbes in biofilms results from properties that are inherent in the biofilm, including enhanced interaction, protection, and biodiversity. Given the diversity of microbes that live in biofilms in harsh environments on the Earth, it is logical to hypothesize that, if microbes inhabit other bodies in the Universe, there are also biofilms on those bodies. The Biofilm Organisms Surfing Space experiment was conducted as part of the EXPOSE-R2 mission on the International Space Station. The experiment was an international collaboration designed to perform a comparative study regarding the survival of biofilms versus planktonic cells of various microorganisms, exposed to space and Mars-like conditions. The objective was to determine whether there are lifestyle-dependent differences to cope with the unique mixture of stress factors, including desiccation, temperature oscillations, vacuum, or a Mars-like gas atmosphere and pressure in combination with extraterrestrial or Mars-like ultraviolet (UV) radiation residing during the long-term space mission. In this study, the outcome of the flight and mission ground reference analysis of Deinococcus geothermalis is presented. Cultural tests demonstrated that D. geothermalis remained viable in the desiccated state, being able to survive space and Mars-like conditions and tolerating high extraterrestrial UV radiation for more than 2 years. Culturability decreased, but was better preserved, in the biofilm consortium than in planktonic cells. These results are correlated to differences in genomic integrity after exposure, as visualized by random amplified polymorphic DNA-polymerase chain reaction. Interestingly, cultivation-independent viability markers such as membrane integrity, ATP content, and intracellular esterase activity remained nearly unaffected, indicating that subpopulations of the cells had survived in a viable but nonculturable state. These findings support the hypothesis of long-term survival of microorganisms under the harsh environmental conditions in space and on Mars to a higher degree if exposed as biofilm.

Deinococcus terrigena sp. nov., a novel member of the family Deinococcaceae.

A bacterial strain, S13-1-2-1T, was isolated from a soil sample collected in Gyeongsangnam-do province, South Korea. Cells were observed to be Gram-stain negative, short rod-shaped and colonies to be pale pink in colour. Analysis of 16S rRNA gene sequences identified this strain as a member of the genus Deinococcus in the family Deinococcaceae, with high levels of sequence similarity with Deinococcus ficus CC-FR2-10T (97.9%) and Deinococcus enclensis NIO-1023T (95.4%). Growth of strain S13-1-2-1T was observed at 10-42 °C, pH 6-8, and in the presence of 0-1.0% NaCl. The isolate was found to exhibit resistance to gamma radiation (D10 10.1 KGy) and UV-light (D10 612 J/m2). The major peptidoglycan amino acids were identified as D-glutamic acid, glycine, alanine and L-ornithine. The predominant respiratory quinone of the strain was identified as menaquinone-8, the major fatty acids were found to be C16:1ω7c (31.4%), C16:0 (18.4%), and C17:1ω8c (17.4%) and the major polar lipids were observed to be an unidentified phosphoglycolipid and an unidentified glycolipid. The genomic DNA G + C content of the strain was determined to be 69.2 mol%. DNA-DNA hybridization with D. ficus showed a relatedness value of 31.5 ± 4.2%. The DNA-DNA hybridization result and the differentiating phenotypic properties clearly indicate that strain S13-1-2-1T represents a novel species in the genus Deinococcus, for which the name Deinococcus terrigena sp. nov. is proposed. The type strain is S13-1-2-1T (= KCTC 33939T = JCM 32248T).

Proteome dynamics during post-desiccation recovery reveal convergence of desiccation and gamma radiation stress response pathways in Deinococcus radiodurans.

Deinococcus radiodurans is inherently resistant to both ionizing radiation and desiccation. Fifteen months of desiccation was found to be the LD50 dose for D. radiodurans. Desiccated cells of D. radiodurans entered 6h of growth arrest during post-desiccation recovery (PDR). Proteome dynamics during PDR were mapped by resolving cellular proteins by 2-dimensional gel electrophoresis coupled with mass spectrometry. At least 41 proteins, represented by 51 spots on proteome profiles, were differentially expressed throughout PDR. High upregulation in expression was observed for DNA repair proteins involved in single strand annealing (DdrA and DdrB), nucleotide excision repair (UvrA and UvrB), homologous recombination (RecA) and other vital proteins that contribute to DNA replication, recombination and repair (Ssb, GyrA and GyrB). Expression of CRP/FNR family transcriptional regulator (Crp) remained high throughout PDR. Other pathways such as cellular detoxification, protein homeostasis and metabolism displayed both, moderately induced and repressed proteins. Functional relevance of proteomic modulations to surviving desiccation stress is discussed in detail. Comparison of our data with the published literature revealed convergence of radiation and desiccation stress responses of D. radiodurans. This is the first report that substantiates the hypothesis that the radiation stress resistance of D. radiodurans is incidental to its desiccation stress resistance.

Radiation resistance in thermophiles: mechanisms and applications.

The study of prokaryotic life in high temperature environments viz., geothermal areas, hot, acidic geysers and undersea hydrothermal vents has revealed the existence of thermophiles (or hyperthermophiles). These microorganisms possess various stress adaptation mechanisms which enable them to bypass multiple physical and chemical barriers for survival. The discovery of radiation resistant thermophile Deinococcus geothermalis has given new insights into the field of radiation microbiology. The ability of radiation resistant thermophiles to deal with the lethal effects of ionizing radiations like DNA damage, oxidative bursts and protein damage has made them a model system for exobiology and interplanetary transmission of life. They might be an antiquity of historical transport process that brought microbial life on Earth. These radiation resistant thermophiles are resistant to desiccation as well and maintain their homeostasis by advance DNA repair mechanisms, reactive oxygen species (ROS) detoxification system and accumulation of compatible solutes. Moreover, engineered radioresistant thermophilic strains are the best candidate for bioremediation of radionuclide waste while the extremolytes produced by these organisms may have predicted therapeutic uses. So, the present article delineate a picture of radiation resistance thermophiles, their adaptive mechanisms to evade stress viz., radiation and desiccation, their present applications along with new horizons in near future.

The Site-Directed A184S Mutation in the HTH Domain of the Global Regulator IrrE Enhances Deinococcus radiodurans R1 Tolerance to UV Radiation and MMC Shock.

IrrE is a highly conserved global regulator in the Deinococcus genus and contributes to survival from high doses of UV radiation, ionizing radiation, and desiccation. Drad-IrrE and Dgob-IrrE from Deinococcus radiodurans and Deinococcus gobiensis I-0 each share 66% sequence identity. However, Dgob-IrrE showed a stronger protection phenotype against UV radiation than Drad- IrrE in the D. radiodurans irrE-deletion mutant (ΔirrE), which may be due to amino acid residues differences around the DNA-binding HTH domain. Site-directed mutagenesis was used to generate a Drad-IrrE A184S single mutant, which has been characterized and compared with the ΔirrE mutant complemented strain with Drad-irrE, designated ΔirrE-E. The effects of the A184S mutation following UV radiation and mitomycin C (MMC) shock were determined. The A184S mutant displayed significantly increased resistance to UV radiation and MMC shock. The corresponding A184 site in Dgob-IrrE was inversely mutated, generating the S131A mutant, which exhibited a loss of resistance against UV radiation, MMC shock, and desiccation. qPCR analysis revealed that critical genes in the DNA repair system, such as recA, pprA, uvrA, and ddrB, were remarkably induced after UV radiation and MMC shock in the ΔirrE-IE and A184S mutants. These data suggested that A184S improves the ability against UV radiation and MMC shock, providing new insights into the modification of IrrE. We speculated that the serine residue may determine the efficiency of DNA binding, leading to the increased expression of IrrE-dependent genes important for protection against DNA damage.

Deinococcus puniceus sp. nov., a bacterium isolated from soil-irradiated gamma radiation.

A Gram-positive, coccus-shaped, crimson-color-pigmented bacterium was isolated from soil irradiated with 5 kGy gamma radiation and was designated strain DY1(T). Cells showed growth at 10-30 °C and pH 7-11 and were oxidase-negative and catalase-positive. Phylogenetic analyses of the 16S rRNA gene showed that the strain DY1(T) belonged to the genus Deinococcus with sequence similarities to Deinococcus aquatilis CCUG 53370(T) (96.2 %) and Deinococcus navajonensis KR-114(T) (94.1 %). Strain DY1(T) showed low level of DNA relatedness with D. aquatilis CCUG 53370(T) (41.3 ± 3.9 %). The DNA G + C content of DY1(T) was 58.7 mol%. Predominant fatty acids were summed feature 3 (C16:1 ω7c/ω6c), C16:0, and C17:0. The major amino acids were D-alanine, L-glutamic acid, glycine, and L-ornithine in the peptidoglycan. The major polar lipids were unknown phosphoglycolipids (PGL). Strain DY1(T) has resistance to gamma radiation and was found to be a novel species. Therefore, the strain was designated as DY1(T) (=KCTC 33027(T) = JCM 18576(T)), and the name Deinococcus puniceus sp. nov. is herein proposed.

RNA sequencing and proteogenomics reveal the importance of leaderless mRNAs in the radiation-tolerant bacterium Deinococcus deserti.

Deinococcus deserti is a desiccation- and radiation-tolerant desert bacterium. Differential RNA sequencing (RNA-seq) was performed to explore the specificities of its transcriptome. Strikingly, for 1,174 (60%) mRNAs, the transcription start site was found exactly at (916 cases, 47%) or very close to the translation initiation codon AUG or GUG. Such proportion of leaderless mRNAs, which may resemble ancestral mRNAs, is unprecedented for a bacterial species. Proteomics showed that leaderless mRNAs are efficiently translated in D. deserti. Interestingly, we also found 173 additional transcripts with a 5'-AUG or 5'-GUG that would make them competent for ribosome binding and translation into novel small polypeptides. Fourteen of these are predicted to be leader peptides involved in transcription attenuation. Another 30 correlated with new gene predictions and/or showed conservation with annotated and nonannotated genes in other Deinococcus species, and five of these novel polypeptides were indeed detected by mass spectrometry. The data also allowed reannotation of the start codon position of 257 genes, including several DNA repair genes. Moreover, several novel highly radiation-induced genes were found, and their potential roles are discussed. On the basis of our RNA-seq and proteogenomics data, we propose that translation of many of the novel leaderless transcripts, which may have resulted from single-nucleotide changes and maintained by selective pressure, provides a new explanation for the generation of a cellular pool of small peptides important for protection of proteins against oxidation and thus for radiation/desiccation tolerance and adaptation to harsh environmental conditions.

Mars' surface radiation environment measured with the Mars Science Laboratory's Curiosity rover.

The Radiation Assessment Detector (RAD) on the Mars Science Laboratory's Curiosity rover began making detailed measurements of the cosmic ray and energetic particle radiation environment on the surface of Mars on 7 August 2012. We report and discuss measurements of the absorbed dose and dose equivalent from galactic cosmic rays and solar energetic particles on the martian surface for ~300 days of observations during the current solar maximum. These measurements provide insight into the radiation hazards associated with a human mission to the surface of Mars and provide an anchor point with which to model the subsurface radiation environment, with implications for microbial survival times of any possible extant or past life, as well as for the preservation of potential organic biosignatures of the ancient martian environment.

FrnE, a cadmium-inducible protein in Deinococcus radiodurans, is characterized as a disulfide isomerase chaperone in vitro and for its role in oxidative stress tolerance in vivo.

Deinococcus radiodurans R1 exposed to a lethal dose of cadmium shows differential expression of a large number of genes, including frnE (drfrnE) and some of those involved in DNA repair and oxidative stress tolerance. The drfrnE::nptII mutant of D. radiodurans showed growth similar to that of the wild type, but its tolerance to 10 mM cadmium and 10 mM diamide decreased by ~15- and ~3-fold, respectively. These cells also showed nearly 6 times less resistance to gamma radiation at 12 kGy and ~2-fold-higher sensitivity to 40 mM hydrogen peroxide than the wild type. In trans expression of drFrnE increased cytotoxicity of dithiothreitol (DTT) in the dsbA mutant of Escherichia coli. Recombinant drFrnE showed disulfide isomerase activity and could maintain insulin in its reduced form in the presence of DTT. While an equimolar ratio of wild-type protein could protect malate dehydrogenase completely from thermal denaturation at 42 °C, the C22S mutant of drFrnE provided reduced protection to malate dehydrogenase from thermal inactivation. These results suggested that drFrnE is a protein disulfide isomerase in vitro and has a role in oxidative stress tolerance of D. radiodurans possibly by protecting the damaged cellular proteins from inactivation.

Pyrroloquinoline quinone and a quinoprotein kinase support γ-radiation resistance in Deinococcus radiodurans and regulate gene expression.

Deinococcus radiodurans is known for its extraordinary resistance to various DNA damaging agents including γ-radiation and desiccation. The pqqE:cat and Δdr2518 mutants making these cells devoid of pyrroloquinoline quinone (PQQ) and a PQQ inducible Ser/Thr protein kinase, respectively, became sensitive to γ-radiation. Transcriptome analysis of these mutants showed differential expression of the genes including those play roles in oxidative stress tolerance and (DSB) repair in D. radiodurans and in genome maintenance and stress response in other bacteria. Escherichia coli cells expressing DR2518 and PQQ showed improved resistance to γ-radiation, which increased further when both DR2518 and PQQ were present together. Although, profiles of genes getting affected in these mutants were different, there were still a few common genes showing similar expression trends in both the mutants and some others as reported earlier in oxyR and pprI mutant of this bacterium. These results suggested that PQQ and DR2518 have independent roles in γ-radiation resistance of D. radiodurans but their co-existence improves radioresistance further, possibly by regulating differential expression of the genes important for bacterial response to oxidative stress and DNA damage.

Pigment-based whole-cell biosensor system for cadmium detection using genetically engineered Deinococcus radiodurans.

In this study, a colorimetric whole-cell biosensor for cadmium (Cd) was designed using a genetically engineered red pigment producing bacterium, Deinococcus radiodurans. Based on the previous microarray data, putative promoter regions of highly Cd-inducible genes (DR_0070, DR_0659, DR_0745, and DR_2626) were screened and used for construction of lacZ reporter gene cassettes. The resultant reporter cassettes were introduced into D. radiodurans R1 to evaluate promoter activity and specificity. Among the promoters, the one derived from DR_0659 showed the highest specificity, sensitivity, and activity in response to Cd. The Cd-inducible activity was retained in the 393-bp deletion fragment (P0659-1) of the P0569 promoter, but the expression pattern of the putative promoter fragments inferred its complex regulation. The detection range was from 10 to 1 mM of Cd. The LacZ expression was increased up to 100 µM of Cd, but sharply decreased at higher concentrations. For macroscopic detection, the sensor plasmid (pRADI-P0659-1) containing crtI as a reporter gene under the control of P0659-1 was introduced into a crtI-deleted mutant strain of D. radiodurans (KDH018). The color of this sensor strain (KDH081) changed from light yellow to red by the addition of Cd and had no significant response to other metals. Color change by the red pigment synthesis could be clearly recognized in a day with the naked eye and the detection range was from 50 nM to 1 mM of Cd. These results indicate that genetically engineered D. radiodurans (KDH081) can be used to monitor the presence of Cd macroscopically.

Oxidative stress resistance in Deinococcus radiodurans.

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.

Effect of relative humidity on Deinococcus radiodurans' resistance to prolonged desiccation, heat, ionizing, germicidal, and environmentally relevant UV radiation.

To test the effect of humidity on the radiation resistance of Deinococcus radiodurans, air-dried cells were irradiated with germicidal 254 nm UV, and simulated environmental UV or γ-radiation and survival was compared to cells in suspension. It was observed that desiccated cells exhibited higher levels of resistance than cells in suspension toward UV or γ-radiation as well as after 85°C heat shock. It was also shown that low relative humidity improves survival during long-term storage of desiccated D. radiodurans cells. It can be concluded that periods or environments in which cells exist in a dehydrated state are beneficial for D. radiodurans' survival exposed to various other stresses.

Deinococcus aerolatus sp. nov. and Deinococcus aerophilus sp. nov., isolated from air samples.

Two strains of pink-coloured bacteria, 5516T-9(T) and 5516T-11(T), were isolated from an air sample collected in Korea. The taxonomic status of these novel strains was investigated by means of a polyphasic approach. The novel strains were Gram-positive, aerobic, non-spore-forming and coccus-shaped bacteria. The DNA G+C contents of strains 5516T-9(T) and 5516T-11(T) were 61.0 and 59.3 mol%, respectively. The major isoprenoid quinone for both strains was MK-8. Strain 5516T-9(T) contained summed feature 3 (iso-C(15 : 0) 2-OH and/or C(16 : 1)omega7c), C(16 : 0) and iso-C(17 : 1)omega9c, and strain 5516T-11(T) contained summed feature 3, iso-C(17 : 1)omega9c, C(17 : 1)omega8c and C(15 : 1)omega6c as the major fatty acids (>10 %). The polar lipid patterns of both strains were similar, comprising one phospholipid and one aminophospholipid as the major components. Phylogenetic analyses using 16S rRNA gene sequences showed that both novel strains were affiliated to the genus Deinococcus. Strain 5516T-9(T) exhibited the highest sequence similarity with Deinococcus marmoris DSM 12784(T) (96.8 %) and strain 5516T-11(T) showed the highest sequence similarity with Deinococcus saxicola DSM 15974(T) (94.5 %). The sequence similarity between strains 5516T-9(T) and 5516T-11(T) was 94.7 %. On the basis of the data presented, it is evident that both strains represent separate novel species of the genus Deinococcus for which the names Deinococcus aerolatus sp. nov. (type strain 5516T-9(T)=KACC 12745(T)=JCM 15442(T)) and Deinococcus aerophilus sp. nov. (type strain 5516T-11(T)=KACC 12746(T)=JCM 15443(T)) are proposed.

Radiation resistance of Deinococcus radiodurans R1 with respect to growth phase.

Deinococcus species exhibit an extraordinary ability to withstand ionizing radiation (IR). Most of the studies on radiation resistance have been carried out with exponential phase cells. The studies on radiation resistance of Deinococcus radiodurans R1 with respect to different phases of growth showed that late stationary phase cells of D. radiodurans R1 were fourfold more sensitive to IR and heat as compared with exponential or early stationary phase cells. The increased sensitivity of D. radiodurans R1 to IR in the late stationary phase was not due to a decrease in the intracellular Mn/Fe ratio or an increase in the level of oxidative protein damage. The resistance to IR was restored when late stationary phase cells were incubated for 15 min in fresh medium before irradiation, indicating that replenishment of exhausted nutrients restored the metabolic capability of the cells to repair DNA damage. These observations suggest that stress tolerance mechanisms in D. radiodurans R1 differ from established paradigms.

Deinococcus gobiensis sp. nov., an extremely radiation-resistant bacterium.

A Gram-positive, non-motile, spherical, red-pigmented and facultatively anaerobic bacterium, designated strain I-0(T), was isolated from a sand sample of the Gobi desert in Xinjiang Autonomous Region, China. Phylogenetic analysis based on 16S rRNA gene sequences indicated that this isolate represents a novel member of the genus Deinococcus, with low sequence similarities (<94 %) to recognized Deinococcus species. The major cellular fatty acids were C(16 : 1)omega7c and C(16 : 0). Its polar lipid profile contained several unidentified glycolipids, phosphoglycolipids, phospholipids, pigments and an aminophospholipid. The peptidoglycan type was Orn-Gly(2) (A3beta) and the predominant respiratory quinone was MK-8. The DNA G+C content was 65.4 mol%. DNA-DNA relatedness between strain I-0(T) and Deinococcus radiodurans ACCC 10492(T) was 37 %. The strain was shown to be extremely resistant to gamma radiation (>15 kGy) and UV light (>600 J m(-2)). On the basis of the phylogenetic, chemotaxonomic and phenotypic data presented, strain I-0(T) represents a novel species of the genus Deinococcus, for which the name Deinococcus gobiensis sp. nov. is proposed. The type strain is I-0(T) (=DSM 21396(T) =CGMCC 1.7299(T)).