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Two Gram-stain-negative bacterial strains, 15-R06ZXC-3 T and R06B22 T , were isolated from the surface sediment of the Arctic Ocean. Phylogenetic analyses based on the 16S rRNA gene and genome sequences indicated that strain 15-R06ZXC-3 T belongs to the genus Thioclava , while strain R06B22 T belongs to the genus Zhongshania . Strain 15-R06ZXC-3 T showed the closest relationship to Thioclava indica DT23-4 T . The digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values between strain 15-R06ZXC-3 T and all of the type strains of the genus Thioclava ranged from 20.8 to 30.4% and 79.1 to 85.7%, respectively. Strain R06B22 T was most closely related to Zhongshania marina DSW25-10 T . The dDDH and ANI values between strain R06B22 T and all of the type strains of the genus Zhongshania ranged from 18.6 to 20.4% and 77.5 to 79.4%, respectively. These dDDH and ANI values were all below the standard cutoff criteria for the delineation of bacterial species, indicating that the two strains may represent novel species within their respective genera. Furthermore, their phenotypic and chemotaxonomic characteristics also differentiated them from closely related species. Based on the polyphasic analyses, strains 15-R06ZXC-3 T and R06B22 T separately represent novel species of the genera Thioclava and Zhongshania , for which the names Thioclava arctica sp. nov. (type strain 15-R06ZXC-3 T = MCCC 1A07434 T = KCTC 8342 T ) and Zhongshania arctica sp. nov. (type strain R06B22 T = MCCC 1A08273 T = KCTC 8343 T ) are proposed. Additionally, phylogenomic analyses showed that the strain Marortus luteolus ZX-21 T was clustered with the strain Z. marina DSW25-10 T and all other type strains of the genus Zhongshania . Furthermore, the ANI and dDDH values between strains ZX-21 T and DSW25-10 T were 97.6% and 78.8±2.5%, respectively, strongly indicating that they represented a single species. Therefore, it is proposed that M. luteolus Yu et al. 2019 be recognized as a later heterotypic synonym of Z. marina On et al. 2019.

A taxonomic study was carried out on strain D104(T), which was isolated from deep-sea subsurface sediment sample from the Arctic Ocean. The bacterium was found to be Gram-negative, oxidase negative and catalase weakly positive, rod shaped, motile by means of polar flagellum. The organism grows between 4 and 37 °C (optimum 25-28 °C) and 0.5-6 % NaCl (optimum 3 %). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain D104(T) belongs to the genus Marinomonas, with highest sequence similarities of 97.7 % to Marinomonas ushuaiensis DSM 15871(T), followed by M. dokdonensis DSW10-10(T) (96.9 %), M. arenicola KMM 3893(T) (96.7 %), M. arctica 328(T) (96.6 %) and other 18 species of the genus Marinomonas (94.4-96.5 %). The average nucleotide identity and estimated DNA-DNA hybridization values between strain D104(T) and M. ushuaiensis DSM 15871(T) were 84.24 % and 20.80 ± 2.33 % respectively. The principal fatty acids were C16:0, sum in feature 3 (C16:1 ω7c/C16:1 ω6c), sum in feature 8 (C18:1 ω7c/C18:1 ω6c) and C12:1 3OH. The G + C content of the chromosomal DNA was determined to be 44.8 mol%. The respiratory quinone was found to be Q8 (100 %). Polar lipids include phosphatidylglycerol and phosphatidylethanolamine as major phospholipids and aminolipid and phospholipid as minor components. The results of the genotypic and phenotypic analyses indicate that strain D104(T) represents a novel species of the genus Marinomonas, for which the name Marinomonas profundimaris sp. nov. is proposed, with the type strain D104(T) (=MCCC 1A07573(T) = LMG 27696(T)).

Objective: To detect the diversity of the degradation bacteria of halogenated-alkane form the surface seawater of the Arctic Ocean., Method: Twelve surface-water samples from the Arctic Ocean were collected and enriched using C16 H33 Cl as the sole carbon and energy source. Bacteria from the enriched cultures were isolated on marine agar, and followed by 16S rRNA gene identification and phylogenetic analysis. Further, their degradation ability was tested with C16 H33 Cl. The bacterial community structures were further examined by denaturing gradient gel electrophoresis (DGGE)., Result: In total 112 isolates were obtained from the 12 samples, of which 19 isolates degraded C16 H33 Cl. Bacteria of Alcanivorax and Rhodococcus exerted good emulsification and degradation, whereas bacteria of Marinobacter also had the degradation capacity, but less. DGGE analysis revealed that Alcanivorax, Parvibaculum and Thioclava were dominated in the enriched consortia., Conclusion: The C16 H33 Cl degradation bacteria in the Arctic marine environment mainly belonged to alpha-proteobacteria, gamma-proteobacteria, actinobacteria and bacteroidetes. This is the first report on the diversity of degradation bacteria of halogenated alkane in the Arctic Ocean. Our result contributed to the knowledge about the arctic environment and the biodiversity of degrading bacteria.