Efficient Biological Decolorization of Malachite Green by Deinococcus wulumuqiensis R12: Process Optimization and Degradation Pathway Analysis

Malachite green (MG) is a toxic triphenylmethane dye widely used in industry, as well as a controversial antimicrobial in aquaculture, leading to environmental concerns. In this study, the conditions for the decolorization of MG by Deinococcus wulumuqiensis R12 were optimized. Under the optimized conditions, a degradation efficiency of 99.30% was achieved for 200 mg/L MG within 30 min, with an initial biomass concentration of 5.5 g/L at 32 °C and pH 5.0. When the initial concentration of MG was increased to 1 g/L, the degradation efficiency surpassed 97% after 2.5 h. Analytical techniques, including UV-VIS, FTIR, GC-MS, and LC-MS analyses revealed that the degradation products included desmethyl-malachite green, di-desmethyl-malachite green, 4-(dimethylamino)benzophenone, and 4-(methylamino)benzophenone, indicating that the MG degradation mechanism of R12 was based on oxidation and demethylation processes. Furthermore, microbial assays confirmed that the byproducts of MG degradation by R12 are much less toxic than the parent compound, indicating the potential of Deinococcus wulumuqiensis R12 as an effective bioremediation agent for MG-contaminated environments.

Structural insights into signaling promiscuity of the CBASS anti-phage defense system from a radiation-resistant bacterium

Radiation-resistant bacteria are of great application potential in various fields, including bioindustry and bioremediation of radioactive waste. However, how radiation-resistant bacteria combat against invading phages is seldom addressed. Here, we present a series of crystal structures of a sensor and an effector of the cyclic oligonucleotide-based anti-phage signaling system (CBASS) from a radioresistant bacterium Deinococcus wulumuqiensis. We found that the sensor CD-NTase enzyme, DwCdnB, can bind all four ribonucleotides and synthesize a variety of cyclic di-nucleotides, including the novel second messenger 3'3'-cyclic di-CMP. Crystal structures of DwCdnB in complex with ATP and dATP provide structural explanations for specific recognition of ribonucleotides via metal coordination with ribose 2'-OH. Crystal structures of DwCdnB in complex with purine and/or pyrimidine nucleotides in the presence of Mg2+ revealed similar binding modes; however, in the presence of Mn2+, the UTP/CTP rotates and flips into the donor pocket and make extensive contacts with additional five residues, suggesting essential role of Mn2+ for catalytic production of cyclic di-pyrimidines. Finally, structural analysis of the downstream effector DwCap5 further provides a structural explanation for its non-specific recognition of a broad range of cyclic di-nucleotides. In sum, this work provides key structural insights into the immune mechanisms of radioresistant bacteria.

Microbe-mediated synthesis of defect-rich CeO2 nanoparticles with oxidase-like activity for colorimetric detection of L-penicillamine and glutathione

To enhance production efficiency, curtail costs, and minimize environmental impact, developing simple and sustainable nanozyme synthesis methods has been the focus of relevant research. In this report, graphite-coated CeO2 nanoparticles (CeO2 NPs) with multiple defects (Ce3+ defects, oxygen vacancies and carbon defects) were synthesized via the culture filtrate of the extremely radioresistant bacterium Deinococcus wulumuqiensis R12 (D. wulumuqiensis R12). The as-prepared CeO2 NPs exhibit remarkable oxidase (OXD)-like activity, efficiently catalyzing the oxidation of the chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB) to form oxTMB, even in the absence of H2O2. The electron-rich bioactive substances in the supernatant were demonstrated to modulate the electronic state of the Ce atom and played a key role in the formation of multiple defects, thereby enhancing the OXD-like activity of CeO2 NPs. Based on the inhibitory effect of sulphydryl groups (-SH) on the TMB-CeO2 system, a colorimetric strategy for the detection of both L-penicillamine (L-PA) and glutathione (GSH) was devised and successfully applied in real sample analysis. The linear ranges of L-PA and GSH detection were found to be 10-500 μM and 9-200 μM with the limits of detection (LODs) at 8.53 and 5.19 μM, respectively. This work provides a straightforward, eco-friendly and nontoxic method for the synthesis and defect construction of CeO2 NPs with OXD-like activity.

Insights into the radiation and oxidative stress mechanisms in genus Deinococcus

Deinococcus species, noted for their exceptional resistance to DNA-damaging environmental stresses, have piqued scientists' interest for decades. This study dives into the complex mechanisms underpinning radiation resistance in the Deinococcus genus. We have examined the genomes of 82 Deinococcus species and classified radiation-resistance proteins manually into five unique curated categories: DNA repair, oxidative stress defense, Ddr and Ppr proteins, regulatory proteins, and miscellaneous resistance components. This classification reveals important information about the various molecular mechanisms used by these extremophiles which have been less explored so far. We also investigated the presence or lack of these proteins in the context of phylogenetic relationships, core, and pan-genomes, which offered light on the evolutionary dynamics of radiation resistance. This comprehensive study provides a deeper understanding of the genetic underpinnings of radiation resistance in the Deinococcus genus, with potential implications for understanding similar mechanisms in other organisms using an interactomics approach. Finally, this study reveals the complexities of radiation resistance mechanisms, providing a comprehensive understanding of the genetic components that allow Deinococcus species to flourish under harsh environments. The findings add to our understanding of the larger spectrum of stress adaption techniques in bacteria and may have applications in sectors ranging from biotechnology to environmental research.

Comparative Metagenomic Analysis of Seed Endobiome of Domesticated and Wild Finger Millet Species (Eleusine spp.): Unveiling Microbial Diversity and Composition

Domestication, which involves selective breeding, modern agricultural practices, and specific growing conditions, can influence the microbial and endophytic communities in crop plants. In this study, we examined the microbial diversity and community composition in the seeds of wild and domesticated finger millet species. We employed a metagenomic approach to investigate the seed microbial diversity and community composition of wild (Eleusine africana) and domesticated finger millet species (Eleusine coracana (L.) Gaertn) grown in the same habitat. While our findings indicated no significant change in seed endobiome diversity due to domestication, there were differences in microbial community composition between wild and domesticated species. Seeds of domesticated species had higher relative abundance of certain bacterial genera including Helicobacter, Akkermansia, Streptococcus, Bacteroides, and Pseudomonas, whereas seeds of wild species had higher relative abundance of unclassified Streptophyta. The seed-associated microbiota also varied among domesticated finger millet accessions. Co-occurrence network analysis revealed a strong relationship between bacteria and fungi in domesticated compared to wild species. We discuss the results obtained in the larger context of the importance of seed endobiome and how domestication processes in crop plants may have impacted the seed endobiome diversity, composition, and function compared to their wild counterparts.

Insights into the synthesis, engineering, and functions of microbial pigments in Deinococcus bacteria

The ability of Deinococcus bacteria to survive in harsh environments, such as high radiation, extreme temperature, and dryness, is mainly attributed to the generation of unique pigments, especially carotenoids. Although the limited number of natural pigments produced by these bacteria restricts their industrial potential, metabolic engineering and synthetic biology can significantly increase pigment yield and expand their application prospects. In this study, we review the properties, biosynthetic pathways, and functions of key enzymes and genes related to these pigments and explore strategies for improving pigment production through gene editing and optimization of culture conditions. Additionally, studies have highlighted the unique role of these pigments in antioxidant activity and radiation resistance, particularly emphasizing the critical functions of deinoxanthin in D. radiodurans. In the future, Deinococcus bacterial pigments will have broad application prospects in the food industry, drug production, and space exploration, where they can serve as radiation indicators and natural antioxidants to protect astronauts' health during long-term space flights.

Deinococcus arenicola sp. nov., a novel radiation-resistant bacterium isolated from sandy soil in Antarctica

A Gram-stain-positive, aerobic, non-mobile and spherical strain, designated ZS9-10T, belonging to the genus Deinococcus was isolated from soil sampled at the Chinese Zhong Shan Station, Antarctica. Growth was observed in the presence of 0-4 % (w/v) NaCl, at pH 7.0-8.0 and at 4-25 °C. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain ZS9-10T formed a lineage in the genus Deinococcus. It exhibited highest sequence similarity (97.4 %) to Deinococcus marmoris DSM 12784T. The major phospholipids of ZS9-10T were unidentified phosphoglycolipid, unidentified glycolipids and unidentified lipids. The major fatty acids were summed feature 3 (C16 : 1  ω7c and/or C16 : 1  ω6c), C16 : 0 and C16 : 1  ω7c. MK-8 was the predominant respiratory quinone. The digital DNA-DNA hybridization and average nucleotide identity values between strain ZS9-10T and its close relative D. marmoris DSM 12784T were 27.4 and 83.9 %, respectively. Based on phenotypic, phylogenetic and genotypic data, a novel species, named Deinococcus arenicola sp. nov., is proposed. The type strain iis ZS9-10T (=CCTCC AB 2019392T=KCTC43192T).

Deinococcus taeanensis sp. nov., a Radiation-Resistant Bacterium Isolated from a Coastal Dune

A Gram-stain-negative, nonspore-forming, nonmotile, aerobic, rod-shaped, and very pale orange-colored bacterial strain, designated TS293^T, was isolated from a sand sample obtained from a coastal dune after exposure to 3kGy of gamma (γ)-radiation. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that the isolate was a member of the genus Deinococcus and clustered with D. deserti VCD115^T. The genome of strain TS293^T was 4.62 Mbp long (68.2% G + C content and 4124 predicted genes) divided into a 2.86Mb main chromosome and five plasmids. Many genes considered to be important to the γ-radiation and oxidative stress resistance of Deinococcus were conserved in TS293^T, but genome features that could differentiate TS293^T from D. deserti and D. radiodurans, the type species of the Deinococcus genus, were also detected. Strain TS293^T showed resistance to γ-radiation with D₁₀ values (i.e., the dose required to reduce the bacterial population by tenfold) of 3.1kGy. The predominant fatty acids of strain TS293^T were summed feature 3 (C_16:1ω6c and/or C_16:1ω7c) and iso-C_16:0. The major polar lipids were two unidentified phosphoglycolipids and one unidentified glycolipid. The main respiratory quinone was menaquinone-8. Based on the phylogenetic, genomic, physiological, and chemotaxonomic characteristics, strain TS293^T represents a novel species, for which the name Deinococcus taeanensis sp. nov. is proposed. The type strain is TS293^T (= KCTC 43191^T = JCM 34027^T).

Complete Genome Sequencing Analysis of Deinococcus wulumuqiensis R12, an Extremely Radiation-Resistant Strain

Genome sequencing was performed by the PacBio RS II platform and Illumina HiSeq 4000 platform to discover the metabolic profile of the Deinococcus wulumuqiensis R12, which was isolated from radiation-contaminated soils in Xinjiang Uygur Autonomous Region of northwest China. The genome of 3.5 Mbp comprises one circular chromosome and four circular plasmids with 3679 genes and a GC content of 66.97%. A total of 41 new transcriptional factors were identified using the DeepTFactor tool. Genomic analysis revealed the presence of genes for homologous recombination repair, which suggested high recombination efficiency in R12. Three Type I and one Type II RM systems, two CRISPR arrays, and one Cas-Type IC protein were found, allowing the development of endogenous CRISPR-Cas gene-editing tools. Additionally, we found that R12 has a broad spectrum of substrate utilization, which was validated by physiological experiments. Genes involved in the carotenoid biosynthesis pathway and the antioxidative system were also identified. Overall, the comprehensive description of the genome of R12 will facilitate the additional exploitation of this strain as a versatile cell factory for biotechnological applications.

Genome based reclassification of Deinococcus swuensis as a heterotypic synonym of Deinococcus radiopugnans

Deinococcus species are widely studied due to their utility in bioremediation of sites contaminated with radioactive elements. In the present study, we re-evaluated the taxonomic placement of two species of the genus Deinococcus namely D. swuensis DY59^T and D. radiopugnans ATCC 19172^T based on whole genome analyses. The 16S rRNA gene analysis revealed a 99.58% sequence similarity between this species pair that is above the recommended threshold value for species delineation. These two species also clustered together in both the 16S rRNA gene and core genome based phylogenies depicting their close relatedness. Furthermore, more than 98% of genes were shared between D. swuensis DY59^T and D. radiopugnans ATCC 19172^T. Interestingly, D. swuensis DY59^T and D. radiopugnans ATCC 19172^T shared high genome similarity in different genomic indices. They displayed an average nucleotide identity value of 97.63%, an average amino acid identity value of 97% and a digital DNA-DNA hybridization value equal to 79.50%, all of which are well above the cut-off for species delineation. Altogether, based on these evidences, D. swuensis DY59^T and D. radiopugnans ATCC 19172^T constitute a single species. Hence, as per the priority of publication, we propose that Deinococcus swuensis Lee et al. 2015 should be reclassified as a later heterotypic synonym of Deinococcus radiopugnans.

Deinococcus psychrotolerans sp. nov., isolated from soil on the South Shetland Islands, Antarctica

A Gram-stain-negative, non-motile, strictly aerobic, coccus-shaped bacterium, designated S14-83^T, was isolated from a soil sample collected from the South Shetland Islands of Antarctica. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the strain is a novel member of the genus Deinococcus, with Deinococcus alpinitundrae as its closest relative (96.1 % similarity). The DNA G+C content of the strain was 61.1 mol% and the major respiratory quinone was MK-8. Major cellular fatty acids were summed feature 3 (C_16 : 1ω7c/C_16 : 1ω6c) and C_16 : 0. As well as containing glycophospholipid, aminophospholipids and glycolipid as major polar lipids, there were also some unknown polar lipids. The diagnostic diamino acid in the cell-wall peptidoglycan was ornithine, corroborating the assignment of the strain to the genus Deinococcus. Strain S14-83^T was shown to be extremely resistant to gamma radiation (>10 kGy) and UV light (460 Jm^-2). On the basis of phylogenetic, chemotaxonomic and phenotypic data presented here, strain S14-83^T represents a novel species of the genus Deinococcus, for which the name Deinococcus psychrotolerans sp. nov. is proposed. The type strain is S14-83^T (=CCTCC AB 2015449^T= DSM 105285 ^T).

Analysis of 1,000 Type-Strain Genomes Improves Taxonomic Classification of Bacteroidetes

Although considerable progress has been made in recent years regarding the classification of bacteria assigned to the phylum Bacteroidetes, there remains a need to further clarify taxonomic relationships within a diverse assemblage that includes organisms of clinical, piscicultural, and ecological importance. Bacteroidetes classification has proved to be difficult, not least when taxonomic decisions rested heavily on interpretation of poorly resolved 16S rRNA gene trees and a limited number of phenotypic features. Here, draft genome sequences of a greatly enlarged collection of genomes of more than 1,000 Bacteroidetes and outgroup type strains were used to infer phylogenetic trees from genome-scale data using the principles drawn from phylogenetic systematics. The majority of taxa were found to be monophyletic but several orders, families and genera, including taxa proposed long ago such as Bacteroides, Cytophaga, and Flavobacterium but also quite recent taxa, as well as a few species were shown to be in need of revision. According proposals are made for the recognition of new orders, families and genera, as well as the transfer of a variety of species to other genera. In addition, emended descriptions are given for many species mainly involving information on DNA G+C content and (approximate) genome size, both of which can be considered valuable taxonomic markers. We detected many incongruities when comparing the results of the present study with existing classifications, which appear to be caused by insufficiently resolved 16S rRNA gene trees or incomplete taxon sampling. The few significant incongruities found between 16S rRNA gene and whole genome trees underline the pitfalls inherent in phylogenies based upon single gene sequences and the impediment in using ordinary bootstrapping in phylogenomic studies, particularly when combined with too narrow gene selections. While a significant degree of phylogenetic conservation was detected in all phenotypic characters investigated, the overall fit to the tree varied considerably, which is one of the probable causes of misclassifications in the past, much like the use of plesiomorphic character states as diagnostic features.

The diversity and commonalities of the radiation-resistance mechanisms of Deinococcus and its up-to-date applications

Deinococcus is an extremophilic microorganism found in a wide range of habitats, including hot springs, radiation-contaminated areas, Antarctic soils, deserts, etc., and shows some of the highest levels of resistance to ionizing radiation known in nature. The highly efficient radiation-protection mechanisms of Deinococcus depend on a combination of passive and active defense mechanisms, including self-repair of DNA damage (homologous recombination, MMR, ER and ESDSA), efficient cellular damage clearance mechanisms (hydrolysis of damaged proteins, overexpression of repair proteins, etc.), and effective clearance of reactive oxygen species (ROS). Due to these mechanisms, Deinococcus cells are highly resistant to oxidation, radiation and desiccation, which makes them potential chassis cells for wide applications in many fields. This article summarizes the latest research on the radiation-resistance mechanisms of Deinococcus and prospects its biotechnological application potentials.

Highly Selective Oxidation of 5-Hydroxymethylfurfural to 5-Hydroxymethyl-2-Furancarboxylic Acid by a Robust Whole-Cell Biocatalyst

Value-added utilization of biomass-derived 5-hydroxymethylfurfural (HMF) to produce useful derivatives is of great interest. In this work, extremely radiation resistant Deinococcus wulumuqiensis R12 was explored for the first time as a new robust biocatalyst for selective oxidation of HMF to 5-hydroxymethylfuroic acid (HMFCA). Its resting cells exhibited excellent catalytic performance in a broad range of pH and temperature values, and extremely high tolerance to HMF and the HMFCA product. An excellent yield of HMFCA (up to 90%) was achieved when the substrate concentration was set to 300 mM under the optimized reaction conditions. In addition, 511 mM of product was obtained within 20 h by employing a fed-batch strategy, affording a productivity of 44 g/L per day. Of significant synthetic interest was the finding that the D. wulumuqiensis R12 cells were able to catalyze the selective oxidation of other structurally diverse aldehydes to their corresponding acids with good yield and high selectivity, indicating broad substrate scope and potential widespread applications in biotechnology and organic chemistry.

Deinococcus fonticola sp. nov., isolated from a radioactive thermal spring in Hungary

A Gram-stain-negative, aerobic, non-motile and coccus-shaped bacterium, designated strain FeSDHB5-19^T, was isolated from a biofilm sample collected from a radioactive thermal spring (Budapest, Hungary), after exposure to 5 kGy gamma radiation. A polyphasic approach was used to study the taxonomic properties of strain FeSDHB5-19^T, which had highest 16S rRNA gene sequence similarity to Deinococcus antarcticus G3-6-20^T (96.5 %). The 16S rRNA gene sequence similarity to type strains of other Deinococcus species were 93.0 % or lower. The DNA G+C content of the draft genome sequence, consisting of 3.9 Mb, was 63.9 mol%. Strain FeSHDB5-19^T was found to grow at temperatures of 10-32 °C (optimum, 28 °C) and pH 5-10 (pH 6.5-7.5) and tolerated up to 1.5 % NaCl (w/v) with optimum growth at 0-0.5 % NaCl. The predominant fatty acids (>10 %) were C16 : 0 and C16 : 1ω7c. The cell-wall peptidoglycan type was A3β l-Orn-Gly1-2. The whole-cell sugars were glucose and low amounts of galactose. Strain FeSDHB5-19^T possessed MK-8 as the predominant respiratory quinone, typical of the genus Deinococcus. The polar lipid profile contained unidentified phosphoglycolipids and unidentified glycolipids. The isolate was found to be highly resistant to gamma (D10<8 kGy) and UV (D10~800 J m^-2) radiation. According to its genotypic, phenotypic and chemotaxonomic characteristics, strain FeSDHB5-19^T represents a novel species in the genus Deinococcus, for which the name Deinococcusfonticola sp. nov. is proposed. The type strain is FeSDHB5-19^T (=NCAIM B.02639^T=DSM 106917^T).

Analysis and expression of the carotenoid biosynthesis genes from Deinococcus wulumuqiensis R12 in engineered Escherichia coli

Deinococcus wulumuqiensis R12 is a red-pigmented extremophilic microorganism with powerful antioxidant properties that was isolated from radiation-contaminated soil in Xinjiang Uyghur Autonomous Region of China. The key carotenoid biosynthesis genes, crtE, crtB and crtI, which are related to the cells’ antioxidant defense, were identified in the sequenced genome of R12 and analyzed. In order to improve the carotenoid yield in engineered Escherichia coli, the origin of carotenoid biosynthesis genes was discussed, and a strain containing the R12 carotenoid biosynthesis genes was constructed to produce lycopene, an important intermediate in carotenoid metabolism. The gene order and fermentation conditions, including the culture medium, temperature, and light, were optimized to obtain a genetically engineered strain with a high lycopene production capacity. The highest lycopene content was 688 mg L⁻¹ in strain IEB, which corresponds to a 2.2-fold improvement over the original recombinant strain EBI.

Deinococcus planocerae sp. nov., isolated from a marine flatworm

A Gram-positive, non-motile and coccoid strain, designated XY-FW106^T, was isolated from a marine flatworm identified to be Planocera sp. The 16S rRNA gene sequence of this pink organism was consistent with membership of the genus Deinococcus, with high sequence similarity to Deinococcus aetherius ST0316^T (94.7%). The optimum growth temperature range of the strain XY-FW106^T was found to be 25-30 °C and optimum growth occurs at pH 7.2-7.4 without NaCl. The strain XY-FW106^T was found to contain unidentified glycolipids, unidentified phosphoglycolipids, unidentified phospholipids and unidentified lipids, which differed from those of closely related species. Menaquinone MK-8 was identified as the major respiratory quinone and the predominant cellular fatty acids were found to be Summed Feature 3 (C_16:1 ω7c/C_16:1 ω6c), C_16:0, iso-C_15:0, and Summed Feature 8 (C_18:1 ω7c/C_18:1 ω6c). The DNA G+C content was determined to be 70.2 mol%. The biochemical and chemotaxonomic data together suggest that the strain represents a new species for which the name Deinococcus planocerae sp. nov. is proposed. The type strain is XY-FW106^T (=MCCC 1K01499^T=KCTC 33809^T).

Deinococcus malanensis sp. nov., isolated from radiation-polluted soil

A Gram-staining positive, non-spore forming, short rod-shaped and coccus-shaped, non-motile, pink-colored, gamma- and UV-resistant strain, designated T93^T was isolated from soil of Malan area in Xinjiang Uyghur Autonomous Region, Northwest China. The taxonomic position of the new isolate was determined using a polyphasic approach. Strain T93^T shared the highest 16 S rRNA gene sequence similarity with Deinococcus deserti VCD115^T (97.54%). The genomic DNA G+C content of the isolate T93^T was 61.7 mol%. The predominant menaquinone was MK-8, while the major cellular fatty acids were iso-C_16:0, C_15:1 ω6c, C_16:0, C_17:1 ω8c and Summed Feature 3 (comprising C_16:1 ω7c and/or C_16:1 ω6c). The major polar lipid profiles consisted of diphosphatidylglycerol and phosphatidylinositol mannoside. Based on the phenotypic and genotypic data, strain T93^T is considered to represent a novel species of the genus Deinococcus, for which the name Deinococcus malanensis sp. nov. is proposed. The type strain is T93^T (= KCTC 33563^T = JCM 30331^T).

Structure, Variation, and Co-occurrence of Soil Microbial Communities in Abandoned Sites of a Rare Earth Elements Mine

Mining activity for rare earth elements (REEs) has caused serious environmental pollution, particularly for soil ecosystems. However, the effects of REEs on soil microbiota are still poorly understood. In this study, soils were collected from abandoned sites of a REEs mine, and the structure, diversity, and co-occurrence patterns of soil microbiota were evaluated by Illumina high-throughput sequencing targeting 16S rRNA genes. Although microbiota developed significantly along with the natural restoration, the microbial structure on the site abandoned for 10 years still significantly differed from that on the unmined site. Potential plant growth promoting bacteria (PGPB) were identified by comparing 16S sequences against a self-constructed PGPB database via BLAST, and it was found that siderophore-producing and phosphorus-solubilizing bacteria were more abundant in the studied soils than in reference soils. Canonical correspondence analysis indicated that species richness of plant community was the prime factor affecting microbial structure, followed by limiting nutrients (total carbon and total nitrogen) and REEs content. Further co-occurring network analysis revealed nonrandom assembly patterns of microbiota in the studied soils. These results increase our understanding of microbial variation and assembly pattern during natural restoration in REE contaminated soils.

Deinococcus saudiensis sp. nov., isolated from desert

Two gamma- and UV-radiation-resistant, pink-coloured bacterial strains, designated YIM F302T and YIM F235, were isolated from the desert of Yanbu' al Bahr located in west of Saudi Arabia. Taxonomic positions of the two isolates were investigated by polyphasic taxonomic approaches. Cells of the two strains were Gram-stain-negative, aerobic and rod-shaped. They were able to grow at 15-45 °C and pH 6.0-8.0 and had a NaCl tolerance limit of 1 % (w/v). Phylogenetic analyses based on 16S rRNA gene sequences revealed that strains YIM F302T and YIM F235 represent members of the genus Deinococcus, sharing highest sequence similarities of 98.3 and 98.4 %, respectively, with Deinococcus grandis DSM 3963T. The strains were found to contain MK-8 as the respiratory menaquinone. Major fatty acids (>10 %) of the two strains were C15 : 1ω6c, C16 : 0 and C16 : 1ω7c. DNA-DNA hybridization values of the two isolates against the closely related type strains were significantly below the 70 % limit for species delineation. Genomic DNA G+C contents of strains YIM F302T and YIM F235 were 69.3 and 69.0 mol%, respectively. Based on the phenotypic and genotypic characteristics recorded, it is determined that the two isolates represent a novel species of the genus Deinococcus, for which the name Deinococcus saudiensis sp. nov. is proposed. The type strain is YIM F302T (=CGMCC 1.15089T=DSM 29933T).

Deinococcus antarcticus sp. nov., isolated from soil

A pink-pigmented, non-motile, coccoid bacterial strain, designated G3-6-20T, was isolated from a soil sample collected in the Grove Mountains, East Antarctica. This strain was resistant to UV irradiation (810 J m−2) and slightly more sensitive to desiccation as compared with Deinococcus radiodurans . Phylogenetic analyses based on the 16S rRNA gene sequence of the isolate indicated that the organism belongs to the genus Deinococcus . Highest sequence similarities were with Deinococcus ficus CC-FR2-10T (93.5 %), Deinococcus xinjiangensis X-82T (92.8 %), Deinococcus indicus Wt/1aT (92.5 %), Deinococcus daejeonensis MJ27T (92.3 %), Deinococcus wulumuqiensis R-12T (92.3 %), Deinococcus aquaticus PB314T (92.2 %) and Deinococcus radiodurans DSM 20539T (92.2 %). Major fatty acids were C18 : 1ω7c, summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), anteiso-C15 : 0 and C16 : 0. The G+C content of the genomic DNA of strain G3-6-20T was 63.1 mol%. Menaquinone 8 (MK-8) was the predominant respiratory quinone. Based on its phylogenetic position, and chemotaxonomic and phenotypic characteristics, strain G3-6-20T represents a novel species of the genus Deinococcus , for which the name Deinococcus antarcticus sp. nov. is proposed. The type strain is G3-6-20T ( = DSM 27864T = CCTCC AB 2013263T).

Reclassification of Deinococcus xibeiensis Wang et al. 2010 as a heterotypic synonym of Deinococcus wulumuqiensis Wang et al. 2010

Two species of the genus Deinococcus, namely Deinococcus wulumuqiensis Wang et al. 2010 and Deinococcus xibeiensis Wang et al. 2010, were simultaneously proposed and described in the same publication. However, the identical 16S rRNA gene sequence of the two type strains strongly raised the probability of their relatedness at the species level. Thus, the genomic relatedness of the two species of the genus Deinococcus was investigated here to clarify their taxonomic status. The high (99.9 %) average nucleotide identity (ANI) between the genome sequences of the two type strains suggested that the two species are synonymous. Additional phenotypic data including enzymic activities and substrate-utilization profiles showed no pronounced differences between the type strains of the two species. Data from this study demonstrated that the two taxa constitute a single species. According to Rule 42 of the Bacteriological Code, we propose that D. xibeiensis Wang et al. 2010 should be reclassified as a subjective heterotypic synonym of D. wulumuqiensis Wang et al. 2010.

Deinococcus citri sp. nov., isolated from citrus leaf canker lesions

A Gram-stain-positive, strictly aerobic, non-motile, coccoid bacterium, designated NCCP-154(T), was isolated from citrus leaf canker lesions and was subjected to a polyphasic taxonomic study. Strain NCCP-154(T) grew at 10-37 °C (optimum 30 °C) and at pH 7.0-8.0 (optimum pH 7.0). The novel strain exhibited tolerance of UV irradiation (>1000 J m(-2)). Based on 16S rRNA gene sequence analysis, strain NCCP-154(T) showed the highest similarity to Deinococcus gobiensis CGMCC 1.7299(T) (98.8 %), and less than 94 % similarity to other closely related taxa. The chemotaxonomic data [major menaquinone, MK-8; cell-wall peptidoglycan type, A3β (Orn-Gly2); major fatty acids, summed feature 3 (C16 : 1ω7c/iso-C15 : 0 2-OH; 35.3 %) followed by C16 : 0 (12.7 %), iso-C17 : 1ω9c (9.2 %), C17 : 1ω8c (7.4 %) and iso-C17 : 0 (6.9 %); major polar lipids made up of several unidentified phosphoglycolipids and glycolipids and an aminophospholipid, and mannose as the predominant whole-cell sugar] also supported the affiliation of strain NCCP-154(T) to the genus Deinococcus. The level of DNA-DNA relatedness between strain NCCP-154(T) and D. gobiensis JCM 16679(T) was 63.3±3.7 %. The DNA G+C content of strain NCCP-154(T) was 70.0 mol%. Based on the phylogenetic analyses, DNA-DNA hybridization and physiological and biochemical characteristics, strain NCCP-154(T) can be differentiated from species with validly published names. Therefore, it represents a novel species of the genus Deinococcus. The name Deinococcus citri sp. nov. is proposed, with the type strain NCCP-154(T) ( = JCM 19024(T) = DSM 24791(T) = KCTC 13793(T)).

Draft Genome Sequence of Deinococcus xibeiensis R13, a New Carotenoid-Producing Strain

Deinococcus xibeiensis strain R13, isolated from radiation-contaminated soils, synthesizes a unique ketocarotenoid, deinoxanthin. Here, we present a 3.49-Mb assembly of its genome sequence, which can help us find the key genes of the deinoxanthin biosynthesis pathways and modify genes obtaining a high yield of the new carotenoid.

Genome Sequence of a Gamma- and UV-Ray-Resistant Strain, Deinococcus wulumuqiensis R12

Deinococcus wulumuqiensis R12, isolated from radiation-polluted soil, is a red-pigmented strain of the extremely radioresistant genus Deinococcus. It contains a major carotenoid, namely, deinoxanthin. Here, we present a 3.39-Mb assembly of its genome sequence, which might provide various kinds of useful information related to Deinococcus, such as about the key enzymes of its radioresistance mechanism and carotenoid biosynthetic pathways.

Radiation-resistant extremophiles and their potential in biotechnology and therapeutics

Extremophiles are organisms able to thrive in extreme environmental conditions. Microorganisms with the ability to survive high doses of radiation are known as radioresistant or radiation-resistant extremophiles. Excessive or intense exposure to radiation (i.e., gamma rays, X-rays, and particularly UV radiation) can induce a variety of mutagenic and cytotoxic DNA lesions, which can lead to different forms of cancer. However, some populations of microorganisms thrive under different types of radiation due to defensive mechanisms provided by primary and secondary metabolic products, i.e., extremolytes and extremozymes. Extremolytes (including scytonemin, mycosporine-like amino acids, shinorine, porphyra-334, palythine, biopterin, and phlorotannin, among others) are able to absorb a wide spectrum of radiation while protecting the organism's DNA from being damaged. The possible commercial applications of extremolytes include anticancer drugs, antioxidants, cell-cycle-blocking agents, and sunscreens, among others. This article aims to review the strategies by which microorganisms thrive in extreme radiation environments and discuss their potential uses in biotechnology and the therapeutic industry. The major challenges that lie ahead are also discussed.

Novel 16S rRNA based PCR method targeting Deinococcus spp. and its application to assess the diversity of deinococcal populations in environmental samples

The members of the genus Deinococcus are extensively studied because of their exemplary radiation resistance. Both ionizing and non-ionizing rays are routinely employed to select upon the radiation resistant deinococcal population and isolate them from the majority of radiation sensitive population. There are no studies on the development of molecular tools for the rapid detection and identification of deinococci from a mixed population without causing the bias of radiation enrichment. Here we present a Deinococcus specific two-step hemi-nested PCR for the rapid detection of deinococci from environmental samples. The method is sensitive and specific to detect deinococci without radiation exposure of the sample. The new protocol was successfully employed to detect deinococci from several soil samples from different geographical regions of India. The PCR method could be adapted to a three-step protocol to study the diversity of the environmental deinococcal population by denaturing gradient gel electrophoresis (DGGE). Sequence analysis of the DGGE bands revealed that the samples harbor diverse populations of deinococci, many of which were not recovered by culturing and may represent novel clades. We demonstrate that the genus specific primers are also suitable for the rapid identification of the bacterial isolates that are obtained from a typical radiation enrichment isolation technique. Therefore the primers and the protocols described in this study can be used to study deinococcal diversity from environmental samples and can be employed for the rapid detection of deinococci in samples or identifying pure culture isolates as Deinococcus species.

Complete genome sequence of Deinococcus maricopensis type strain (LB-34)

Deinococcus maricopensis (Rainey and da Costa 2005) is a member of the genus Deinococcus, which is comprised of 44 validly named species and is located within the deeply branching bacterial phylum Deinococcus-Thermus. Strain LB-34(T) was isolated from a soil sample from the Sonoran Desert in Arizona. Various species of the genus Deinococcus are characterized by extreme radiation resistance, with D. maricopensis being resistant in excess of 10 kGy. Even though the genomes of three Deinococcus species, D. radiodurans, D. geothermalis and D. deserti, have already been published, no special physiological characteristic is currently known that is unique to this group. It is therefore of special interest to analyze the genomes of additional species of the genus Deinococcus to better understand how these species adapted to gamma- or UV ionizing-radiation. The 3,498,530 bp long genome of D. maricopensis with its 3,301 protein-coding and 66 RNA genes consists of one circular chromosome and is a part of the Genomic Encyclopedia of Bacteria and Archaea project.