Marine environments are a rich source of Actinobacteria and have the potential to produce a wide variety of biologically active secondary metabolites. In this study, we used four selective isolation media to culture Actinobacteria from the sediments collected from the Chukchi Shelf in the Arctic Ocean. A total of 73 actinobacterial strains were isolated. Based on repetitive DNA fingerprinting analysis, we selected 30 representatives for partial characterization according to their phylogenetic diversity, antimicrobial activities and secondary-metabolite biosynthesis genes. Results from the 16S rRNA gene sequence analysis indicated that the 30 strains could be sorted into 18 phylotypes belonging to 14 different genera: Agrococcus, Arsenicicoccus, Arthrobacter, Brevibacterium, Citricoccus, Janibacter, Kocuria, Microbacterium, Microlunatus, Nocardioides, Nocardiopsis, Saccharopolyspora, Salinibacterium and Streptomyces. To our knowledge, this paper is the first report on the isolation of Microlunatus genus members from marine habitats. Of the 30 isolates, 11 strains exhibited antibacterial and/or antifungal activity, seven of which have activities against Bacillus subtilis and Candida albicans. All 30 strains have at least two biosynthetic genes, one-third of which possess more than four biosynthetic genes. This study demonstrates the significant diversity of Actinobacteria in the Chukchi Shelf sediment and their potential for producing biologically active compounds and novel material for genetic manipulation or combinatorial biosynthesis.

Strain 20041T was isolated from sea-ice of the Canadian Basin (7 ° 23′ 14″ N 14 ° 06′ 55″ W). Phylogenetic analysis based on 16S rRNA gene homology showed that strain 20041T was related to members of the genus Marinobacter and had highest 16S rRNA gene sequence similarity with the type strain of Marinobacter maritimus. Cells were Gram-negative, rod-shaped, psychrophilic and motile. The temperature range for growth was 0–22 °C, with optimum growth occurring at 16–18 °C and at approximately pH 6.0–9.0. Strain 20041T had ubiquinone-9 as the major respiratory quinone and iso-C15 : 0 2OH and/or C16 : 1 ω7c, C16 : 0, C18 : 1 ω9c and C12 : 0 3OH as major fatty acids. The genomic DNA G+C content was 55.4 mol%. On the basis of the phenotypic characteristics, phylogenetic analysis and DNA–DNA relatedness data, strain 20041T is considered to represent a novel species, for which the name Marinobacter psychrophilus sp. nov. is proposed. The type strain is 20041T (=CGMCC 1.6499T=JCM 14643T).

A Gram-negative, psychrophilic, motile, rod-shaped bacterium, designated strain 20188T, was isolated from marine samples collected from the Arctic (7 ° 00′ 24″ N 16 ° 59′ 37″ W), and was identified taxonomically by means of a polyphasic study. On the basis of 16S rRNA gene sequence similarity, strain 20188T was closely related to members of the genera Phaeobacter. 16S rRNA gene sequence similarities between strain 20188T and the type strains of Phaeobacter inhibens, Phaeobacter gallaeciensis and Phaeobacter daeponensis were 97.0, 96.8 and 96.2 %, respectively. The temperature range for growth was 0–25 °C, with optimum growth occurring at 19–20 °C and at approximately pH 6.0–9.0. Strain 20188T had ubiquinone-10 as the major respiratory quinone and C18 : 1 ω7c and 11-methyl C18 : 1 ω7c as major fatty acids. The genomic DNA G+C content was 59.6 mol%. On the basis of phenotypic characteristics, phylogenetic analysis and DNA–DNA relatedness data, strain 20188T is considered to represent a novel species of the genus Phaeobacter, for which the name Phaeobacter arcticus sp. nov. is proposed. The type strain is 20188T (=CGMCC 1.6500T=JCM 14644T).

The diversity and cold-active hydrolytic enzymes of culturable bacteria associated with sandy sediment from Nella Fjord, Eastern Antarctica (69°22′6″ S, 76°21′45″ E) was investigated. A total of 33 aerobic heterotrophic bacterial strains were isolated at 4 °C. These bacterial isolates could be sorted into 18 phylotypes based on the 16S rRNA gene sequence belonging to four phyla, namely Alphaproteobacteria, Gammaproteobacteria, Bacteroidetes and Actinobacteria. Only seven isolates were psychrophilic, 15 isolates were moderately psychrophilic, and 11 isolates were psychrotolerant. More than 72% of the isolates required sodium chloride to grow. Esterase, b-glucosidase and proteases activities at 4 °C were detected in more than 45% of the strains while approximately 21%, 15% and 12% of the strains possessed lipase, amylase and chitinase, respectively. These results indicate that a relatively high culturable bacterial diversity is present within marine sediment of Nella Fjord and it could serve as an ideal candidate region for bioprospecting.

A novel psychrotolerant bacterial strain, BCw111^T, was isolated from seawater samples from the Chukchi Sea in the Arctic Ocean. Cells of strain BCw111^T were Gram-negative, motile, facultatively anaerobic, curved rods and were able to grow at 0–30 °C (optimum 23–25 °C). Strain BCw111^T had Q-8 as the major respiratory quinone and contained iso-C_15 : 0 2-OH and/or C_16 : 1ω7c (28.13 %), C_16 : 0 (13.28 %) and C_17 : 1 (12.90 %) as the major cellular fatty acids. The genomic DNA G+C content was 41.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain BCw11^T formed a distinct lineage within the genus Colwellia and exhibited the highest 16S rRNA gene sequence similarity with Colwellia polaris 537^T (97.8 %) and Colwellia aestuarii SMK-10^T (97.1 %). Based on phenotypic characteristics, phylogenetic analysis and DNA–DNA relatedness, a novel species, Colwellia chukchiensis sp. nov., is proposed. The type strain is BCw111^T ( = CGMCC 1.9127^T = LMG 25329^T = DSM 22576^T).