Bacteria in the genus Arthrobacter have been found in extreme environments, e.g. glaciers, brine and mural paintings. Here, we report the discovery of a novel pink-coloured bacterium, strain QL17(T), capable of producing an extracellular water-soluble blue pigment. The bacterium was isolated from the soil of the East Rongbuk Glacier of Mt. Everest, China. 16S rRNA gene sequence analysis showed that strain QL17(T) was most closely related to the species Arthrobacter bussei KR32 (T). However, compared to A.bussei KR32(T) and the next closest relatives, the new species demonstrates considerable phylogenetic distance at the whole-genome level, with an average nucleotide identity of <85 % and inferred DNA-DNA hybridization of <30 %. Polyphasic taxonomy results support our conclusion that strain QL17(T) represents a novel species of the genus Arthrobacter. Strain QL17(T) had the highest tolerance to hydrogen peroxide at 400 mM. Whole-genome sequencing of strain QL17(T) revealed the presence of numer-ous cold-adaptation, antioxidation and UV resistance-associated genes, which are related to adaptation to the extreme envi-ronment of Mt. Everest. Results of this study characterized a novel psychrotolerant Arthrobacter species, for which the name Arthrobacter antioxidans sp. nov. is proposed. The type strain is QL17(T) (GDMCC 1.2948(T)=JCM 35246(T)).

Gram-stain-negative, aerobic, rod-shaped, non-motile bacterium strain ZFBP2030(T) was isolated from a rock on the North slope of Mount Everest. This strain contained a unique ubiquinone-10 (Q-10) as a predominant respiratory quinone. Among the tested fatty acids, the strain contained summed feature 8, C-14:0 2OH, and C-16:0, as major cellular fatty acids. The polar lipid profile contained phosphatidyl glycerol, phosphatidyl ethanolamine, three unidentified phospholipids, two unidentified aminolipids, and six unidentified lipids. The cell-wall peptidoglycan was a meso-diaminopimelic acid, and cell-wall sugars were ribose and galactose. Phylogenetic analyses based on 16S rRNA gene sequence revealed that strain ZFBP2030(T) was a member of the genus Sphingomonas, exhibiting high sequence similarity to the 16S rRNA gene sequences of Sphingomonas aliaeris DH-S5(T) (97.9%), Sphingomonas alpina DSM 22537(T) (97.3%) and Sphingomonas hylomeconis CCTCC AB 2013304(T) (97.0%). The 16S rRNA gene sequence similarity between ZFBP2030(T) and other typical strains was less than 97.0%. The average amino acid identity values, average nucleotide identity, and digital DNA-DNA hybridization values between strain ZFBP2030(T) and its highest sequence similarity strains were 56.9-79.9%, 65.1-82.2%, and 19.3-25.8%, respectively. The whole-genome size of the novel strain ZFBP2030(T) was 4.1 Mbp, annotated with 3838 protein-coding genes and 54 RNA genes. Moreover, DNA G + C content was 64.7 mol%. Stress-related functions predicted in the subsystem classification of the strain ZFBP2030(T) genome included osmotic, oxidative, cold/heat shock, detoxification, and periplasmic stress responses. The overall results of this study clearly showed that strain ZFBP2030(T) is a novel species of the genus Sphingomonas, for which the name Sphingomonas endolithica sp. nov. is proposed. The type of strain is ZFBP2030(T) (= EE 013(T) = GDMCC 1.3123(T) = JCM 35386(T)).

Mount Everest provides natural advantages to finding radiation-resistant extremophiles that are functionally mechanistic and possess commercial significance. (1) Background: Two bacterial strains, designated S5-59T and S8-45T, were isolated from moraine samples collected from the north slope of Mount Everest at altitudes of 5700m and 5100m above sea level. (2) Methods: The present study investigated the polyphasic features and genomic characteristics of S5-59(T) and S8-45(T). (3) Results: The major fatty acids and the predominant respiratory menaquinone of S5-59(T) and S8-45(T) were summed as feature 3 (comprising C16:1 omega 6c and/or C16:1 omega 7c) and ubiquinone-10 (Q-10). Phylogenetic analyses based on 16S rRNA sequences and average nucleotide identity values among these two strains and their reference type strains were below the species demarcation thresholds of 98.65% and 95%. Strains S5-59(T) and S8-45(T) harbored great radiation resistance. The genomic analyses showed that DNA damage repair genes, such as mutL, mutS, radA, radC, recF, recN, etc., were present in the S5-59(T) and S8-45(T) strains. Additionally, strain S5-59(T) possessed more genes related to DNA protection proteins. The pan-genome analysis and horizontal gene transfers revealed that strains of Sphingomonas had a consistently homologous genetic evolutionary radiation resistance. Moreover, enzymatic antioxidative proteins also served critical roles in converting ROS into harmless molecules that resulted in resistance to radiation. Further, pigments and carotenoids such as zeaxanthin and alkylresorcinols of the non-enzymatic antioxidative system were also predicted to protect them from radiation. (4) Conclusions: Type strains S5-59(T) (=JCM 35564T =GDMCC 1.3193T) and S8-45(T) (=JCM 34749T =GDMCC 1.2715T) represent two novel species of the genus Sphingomonas with the proposed name Sphingomonas qomolangmaensis sp. nov. and Sphingomonas glaciei sp. nov. The type strains, S5-59(T) and S8-45(T), were assessed in a deeply genomic study of their radiation-resistant mechanisms and this thus resulted in a further understanding of their greater potential application for the development of anti-radiation protective drugs.

We isolated and analyzed a novel, Gram-stain-positive, aerobic, rod-shaped, non-motile actinobacterium, designated as strain ZFBP1038(T), from rock sampled on the north slope of Mount Everest. The growth requirements of this strain were 10-37 degree celsius, pH 4-10, and 0-6% (w/v) NaCl. The sole respiratory quinone was MK-9, and the major fatty acids were anteiso-C-15:0 and iso-C-17:0. Peptidoglycan containing meso-diaminopimelic acid, ribose, and glucose were the major cell wall sugars, while polar lipids included diphosphatidyl glycerol, phosphatidyl glycerol, an unidentified phospholipid, and an unidentified glycolipid. A phylogenetic analysis based on 16S rRNA gene sequences showed that strain ZFBP1038(T) has the highest similarity with Spelaeicoccus albus DSM 26341( T) (96.02%). ZFBP1038(T) formed a distinct monophyletic clade within the family Brevibacteriaceae and was distantly related to the genus Spelaeicoccus. The G + C content of strain ZFBP1038(T) was 63.65 mol% and the genome size was 4.05 Mb. Digital DNA-DNA hybridization, average nucleotide identity, and average amino acid identity values between the genomes of strain ZFBP1038(T) and representative reference strains were 19.3-25.2, 68.0-71.0, and 52.8-60.1%, respectively. Phylogenetic, phenotypic, and chemotaxonomic characteristics as well as comparative genome analyses suggested that strain ZFBP1038(T) represents a novel species of a new genus, for which the name Saxibacter gen. nov., sp. nov. was assigned with the type strain Saxibacter everestensis ZFBP1038(T) (= EE 014( T) = GDMCC 1.3024( T) = JCM 35335( T)).

A bacterial strain, designated S9-5(T), was isolated from moraine samples collected from the north slope of Mount Everest at an altitude of 5500 m above sea level. A polyphasic study confirmed the affiliation of the strain with the genus Sphingomonas. Strain S9-5(T) was an aerobic, Gram-stain-negative, non-spore-forming, non-motile and rod-shaped bacterium that could grow at 10-40 degrees C, pH 5-8 and with 0-9% (w/v) NaCl. Q-10 was its predominant respiratory menaquinone. Diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, an unidentified phospholipid, an unidentified aminophospholipid and eight unidentified lipids comprised the polar lipids of strain S9-5(T). Its major fatty acids were summed feature 8 (C-18:1 omega 7c and/or C-18:1 omega 6c) and C-16:0. The G+C content was 65.75mol%. Phylogenetic analysis based on 16S rRNA sequences showed that strain S9-5(T) was phylogenetically closely related to Sphingomonas panaciterrae DCY91(T) (98.17%), Sphingomonas olei K-1-16(T) (98.11%) and Sphingomonas mucosissima DSM 17494(T) (97.39%). The average nucleotide identity values among strain S9-5(T) and Sphingomonas panaciterrae DCY91(T), Sphingomonas olei K-1-16(T) and Sphingomonas mucosissima DSM 17494(T) were 78.82, 78.87 and 78.29%, respectively. Based on the morphological, physiological and chemotaxonomic data, strain S9-5(T) (=JCM 34750(T)=GDMCC 1.2714(T)) should represent a novel species of the genus Sphingomonas, for which we propose the name Sphingomonas radio-durans sp. nov.