Marinifilum caeruleilacunae sp. nov., isolated from Yongle Blue Hole in the South China Sea.

A Gram-stain-negative, non-motile, facultatively anaerobic and non-flagellated marine bacterium, designated JC070T was isolated from the Yongle Blue Hole in the South China Sea. The temperature, pH and NaCl ranges for growth of strain JC070T were 4-37 °C (optimum, 16 °C), pH 6.0-9.0 (optimum, pH 7.0) and 1.0 -6.0% (w/v; optimum, 3.0%). The predominant isoprenoid quinone of strain JC070T was identified as menaquinone-7. The dominant fatty acids (>10%) were iso-C15:0 (59.6%) and iso-C17:0 3-OH (17.2%). The major polar lipids were aminophospholipid, aminolipid, two unknown phospholipids and two unidentified lipids. The genomic DNA G+C content was determined to be 37.0 mol%. Based on the results of polyphasic analysis, a new species, named Marinifilum caeruleilacunae sp. nov., within the genus Marinifilum was proposed. The type strain is JC070T (= JCM 39045T=MCCC 1K03774T).

Viral Characteristics of the Warm Atlantic and Cold Arctic Water Masses in the Nordic Seas.

Nordic Seas are the subarctic seas connecting the Arctic Ocean and North Atlantic Ocean with complex water masses, experiencing an abrupt climate change. Though knowledge of the marine virosphere has expanded rapidly, the diversity of viruses and their relationships with host cells and water masses in the Nordic Seas remain to be fully revealed. Here, we establish the Nordic Sea DNA virome (NSV) data set of 55,315 viral contigs including 1,478 unique viral populations from seven stations influenced by both the warm Atlantic and cold Arctic water masses. Caudovirales dominated in the seven NSVs, especially in the warm Atlantic waters. The major giant nucleocytoplasmic large DNA viruses (NCLDVs) contributed a significant proportion of the classified viral contigs in the NSVs (32.2%), especially in the cold Arctic waters (44.9%). The distribution patterns of Caudovirales and NCLDVs were a reflection of the community structure of their hosts in the corresponding water masses and currents. Latitude, pH, and flow speed were found to be key factors influencing the microbial communities and coinfluencing the variation of viral communities. Network analysis illustrated the tight coupling between the variation of viral communities and microbial communities in the Nordic Seas. This study suggests a probable linkage between viromes, host cells, and surface water masses from both the cool Arctic and warm Atlantic Oceans. IMPORTANCE This is a systematic study of Nordic Sea viromes using metagenomic analysis. The viral diversity, community structure, and their relationships with host cells and the complex water masses from both the cool Arctic and the warm Atlantic oceans were illustrated. The NCLDVs and Caudovirales are proposed as the viral characteristics of the cold Arctic and warm Atlantic waters, respectively. This study provides an important background for the viromes in the subarctic seas connecting the Arctic Ocean and North Atlantic Ocean and sheds light on their responses to abrupt climate change in the future.

Vertical diversity and association pattern of total, abundant and rare microbial communities in deep-sea sediments.

Microbial abundance and community composition in marine sediments have been widely explored. However, high-resolution vertical changes of benthic microbial diversity and co-occurrence patterns are poorly described. The ecological contributions of abundant and rare species in sediments also remain largely unknown. Here, by analysing microbial populations at 14 depth layers of 10 subseafloor sediment cores (water depth 1,250-3,530 m) obtained in the South China Sea, we provided the vertical profiles of microbial ß-diversity and co-occurrence influenced by subcommunities of different abundance. These 134 sediment samples were clustered into four groups according to sediment depth (1-2, 6-10, 30-90 and 190-790 cm) with obvious shifts in microbial community compositions. The vertical succession of microorganisms was consistent with redox zonation and influenced by terrestrial inputs. Partitioning of vertical ß-diversity showed extremely high species replacement between deep layers and the surface layer, indicating selection-induced loss of rare species and dispersal of dormant cells and spores. By contrast, for horizontal ß-diversity, richness of rare species became increasingly significant in deep sediments. Accompanying this ß-diversity profile were clear changes in the association pattern, with microorganisms being less connected in deeper sediment layers, probably reflecting reduced syntrophic interactions. Rare species accounted for an indispensable proportion in the co-occurrence network, and tended to form complex "small worlds." The rare subcommunity also responded differently to various environmental factors compared with the abundant subcommunity. Our findings expand current knowledge on vertical changes of marine benthic microbial diversity and their association patterns, emphasizing the potential roles of rare species.

Ancylomarina longa sp. nov., isolated from southern Okinawa Trough sediment and emended description of the family Marinifilaceae.

A Gram-stain-negative, obligately anaerobic, non-motile, non-spore-forming, long-rod-shaped and non-flagellated bacterial strain, designated T3-2 S1-CT, was isolated from a sediment sample collected at the Okinawa Trough. Phylogenetic analyses of 16S rRNA gene sequences and the whole genome revealed that strain T3-2 S1-CT was a member of the family Marinifilaceae and exhibited less than 95.1 % sequence similarities to the closely related type strains of the family Marinifilaceae. Optimal growth occurred at pH 7.0, 28 °C and in the presence of 3 % (w/v) NaCl. The isoprenoid quinone of strain T3-2 S1-CT was identified as menaquinone-7 (MK-7) and the predominant fatty acids (>10 %) were iso-C15 : 0 (38.9 %) and anteiso-C15 : 0 (11.6 %). The major polar lipids were one phosphatidylethanolamine, one phosphatidylmonomethylethanolamine, one aminolipids, two unidentified lipids and two unidentified phospholipids. The DNA G+C content of strain T3-2 S1-CT was 35.7 mol%. On the basis of the results of polyphasic analyses, strain T3-2 S1-CT is considered to represent a novel species of the genus Ancylomarina, for which the name Ancylomarina longa sp. nov. is proposed. The type strain is T3-2 S1-CT (=KCTC 15505T=MCCC 1K01617T).

Puteibacter caeruleilacunae gen. nov., sp. nov., a facultatively anaerobic bacterium isolated from Yongle Blue Hole in the South China Sea.

Blue holes are unique geomorphological units characterized by steep redox and biogeochemical gradients. Yongle Blue Hole is located on the largest atoll (Yongle Atoll) of the western Xisha Islands in the South China Sea. A Gram-stain-negative, facultatively anaerobic, non-motile, non-flagellated marine bacterium with creamy white colonies, designated JC036T, was isolated from Yongle Blue Hole. Cells were short-rod-shaped and catalase-negative. 16S rRNA gene sequence analysis showed that sequence similarities were lower than 91.6 % against all validly named species in the family Prolixibacteraceae; a reconstructed phylogenetic tree indicated that strain JC036T formed a lineage with strains in the family Prolixibacteraceae. Growth occurred at 4-37 °C (optimum, 28 °C), at pH 5.0-9.0 (optimum, 7.0) and in the presence of 2-6 % (w/v) NaCl (optimum, 3 %). The prevalent isoprenoid quinone of strain JC036T was menaquinone-7 (MK-7). Iso-C15 : 0 and iso-C17 : 0 3-OH were the predominant fatty acids. The major polar lipids included a phospholipid, phosphatidylethanolamine, an aminophospholipid and four unidentified lipids. The genomic DNA G+C content of strain JC036T was 37.8 mol%. Based on physiological and biochemical characteristics and whole genome comparisons, we propose a new genus and species, Puteibacter caeruleilacunae gen. nov., sp. nov., within the family Prolixibacteraceae. The type strain of Puteibacter caeruleilacunae is JC036T (=JCM 33128T=MCCC 1K03579T). From this study, a deeper understanding of the community of the microorganism and their roles in biogeochemical cycles, especially anaerobic bacteria, is provided.

Characterization and overexpression of a glycosyl hydrolase family 16 beta-agarase YM01-1 from marine bacterium Catenovulum agarivorans YM01T.

Agar, usually extracted from seaweed, has a wide variety of industrial applications due to its gelling and stabilizing characteristics. Agarases are the enzymes which hydrolyze agar into agar oligosaccharides. The produced agar oligosaccharides have been widely used in cosmetic, food, and medical fields due to their biological functions. A beta-agarase gene, YM01-1, was cloned and expressed from a marine bacterium Catenovulum agarivorans YM01T. The encoding agarase of YM01-1 consisted of 331 amino acids with an apparent molecular mass of 37.7 kDa and a 23-amino-acids signal peptide. YM01-1 belongs to glycoside hydrolase 16 (GH16) family based on the amino acid sequence homology. The optimum pH and temperature for its activity was 7.0 and 50 °C, respectively. YM01-1 was stable at a pH of pH 6.0-9.0 and temperatures below 45 °C. Thin layer chromatography (TLC) and ion trap mass spectrometer of the YM01-1 hydrolysis products displayed that YM01-1 was an endo-type ß-agarase and degrades agarose, neoagarohexaose, neoagarotetraose into neoagarobiose. The Km, Vmax, Kcat and Kcat/Km values of the YM01-1 for agarose were 8.69 mg/ml, 4.35 × 103 U/mg, 2.4 × 103 s-1 and 2.7 × 106 s-1 M-1, respectively. Hence, the enzyme with high agarolytic activity and single end product was different from other GH16 agarases, which has potential applications for the production of oligosaccharides with remarkable activities.

Marinifilum breve sp. nov., a marine bacterium isolated from the Yongle Blue Hole in the South China Sea and emended description of the genus Marinifilum.

A Gram-stain-negative, facultative anaerobic, non-motile, short-clavate and non-flagellated marine bacterium strain, designated JC075T, was isolated from the Yongle Blue Hole in the South China Sea. Based on the 16S rRNA gene sequence, strain JC075T was found to be closely related to Marinifilum albidiflavum FB208T (97.10 %), Marinifilum flexuosum DSM 21950T (96.43 %) and Marinifilum fragile JCM 15579T (95.58 %), with less than 90.24 % sequence similarity to other genera of the family Marinifilaceae. The growth temperature was in the range of 10-37 °C, and the optimum temperature was 16 °C. Optimal growth occurred at pH 7.0 and in the presence of 3 % (w/v) NaCl. The isoprenoid quinone of strain JC075T was identified as menaquinone-7 and the predominant fatty acids (>10 %) were iso-C15 : 0 (47.9 %), summed feature 9 (C17 : 1 or/and iso-C17 : 1ω9c; 18.7 %) and iso-C17 : 0 3-OH (14.9 %). The major polar lipids were one phosphatidylethanolamine, one phospholipid, one aminophospholipid, one glycolipid, one aminolipid and two unidentified lipids. The DNA G+C content of strain JC075T was 35.8 mol%. On the basis of polyphasic analysis, strain JC075T was considered to represent a novel species of the genus Marinifilum, for which the name Marinifilumbreve sp. nov. is proposed. The type strain is JC075T (=KCTC 15646T=MCCC 1K03477T=JCM 32401T).

Flavobacterium ovatum sp. nov., a marine bacterium isolated from an Antarctic intertidal sandy beach.

A rod-shaped, Gram-staining-negative, strictly aerobic, non-motile bacterium with no flexirubin-type pigment, designated as W201ET, was isolated from an intertidal sandy beach in Antarctica. The organism formed faintly yellow, round colonies on marine agar 2216E. The strain required sea salts for growth and grew optimally in the presence of 2 % (w/v) NaCl at pH 7.0, 20 °C. Phylogenetic analysis based on 16S rRNA gene sequence indicated that strain W201ET belonged to the genus Flavobacterium and showed the highest sequence similarity to Flavobacterium algicola NBRC 102673T (96.5 %). The major respiratory quinone was menaquinone 6, and the predominant fatty acids were iso-C15 : 1 G, iso-C15 : 0, iso-C15 : 0 3-OH and summed feature 3 (which comprises C16 : 1ω7c and/or C16 : 1ω6c). The polar lipids of strain W201ET comprised one phosphatidylethanolamine, two unidentified aminolipids and three unidentified polar lipids. The DNA G+C content of strain W201ET was 34.1 mol%. On the basis of the polyphasic analyses, this isolate was considered to represent a novel species in the genus Flavobacterium, for which the name Flavobacterium ovatum sp. nov. is proposed. The type strain is W201ET (=KCTC 52693T=MCCC 1K03251T=CGMCC 1.16053T).

Ancylomarina psychrotolerans sp. nov., isolated from sediments of Fildes Peninsula and emended the description of genus Ancylomarina.

A Gram-stain negative, obligately anaerobic, non-motile, asporogenous long rod-shaped and non-flagellated bacterial strain, designated 4SWWS2-6T, was isolated from sediment in the intertidal zone of Fildes Peninsula, Antarctica. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain 4SWWS2-6T belongs to the genus Ancylomarina and showed high sequence similarity with Ancylomarina subtilis FA102T (96.5%). Optimal growth occurred at pH 6.5, 16 °C and in the presence of 3% (w/v) NaCl. Strain 4SWWS2-6T contained menaquinone-7 (MK-7) as the major respiratory quinone and held iso-C15:0, anteiso-C15:0 and iso-C15:0 3-OH as the major cellular fatty acids. The major polar lipids were phosphatidylethanolamine, phosphatidylmonomethylethanolamine, an aminolipid, two unidentified lipids and an unidentified phospholipid. The DNA G + C content of strain 4SWWS2-6T was 37.6 mol%. On the basis of the polyphasic analyses, strain 4SWWS2-6T is considered to represent a novel species in the genus Ancylomarina, for which the name Ancylomarina psychrotolerans sp. nov. is proposed. The type strain is 4SWWS2-6T (= KCTC 15504T = MCCC 1K01618T).

Polaribacter pacificus sp. nov., isolated from a deep-sea polymetallic nodule from the Eastern Pacific Ocean.

A Gram-staining-negative, yellow-colony-forming, rod-shaped, non-flagellated and facultatively aerobic strain, designed HRA130-1T, was isolated from a deep-sea polymetallic nodule from the Pacific Clarion-Clipperton Fracture Zone (CCFZ). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain HRA130-1T belonged to the genus Polaribacter (96.3-93.2 % 16S rRNA gene sequence similarity), and exhibited 94 % 16S rRNA gene sequence similarity to Polaribacter filamentus KCTC 23135T (type species) and the highest sequence similarity to Polaribacter huanghezhanensis KCTC 32516T (96.3 %). Optimal growth occurred in the presence of 4 % (w/v) NaCl, at pH 7.0 and 16 °C. The DNA G+C content of strain HRA130-1T was 35.9 mol%. The major fatty acid was iso-C15 : 0. The predominant respiratory quinone was menaquinone-6 (MK-6). The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol, one unidentified phospholipid and an unidentified aminolipid. On the basis of data from the present taxonomic study using a polyphasic approach, strain HRA130-1T represents a novel species of the genus Polaribacter, for which the name Polaribacter pacificus sp. nov. is proposed. The type strain is HRA130-1T (=KCTC 52370T=MCCC 1K03199T=JCM 31460T=CGMCC 1.15763T).

Xuhuaishuia manganoxidans gen. nov., sp. nov., a manganese-oxidizing bacterium isolated from deep-sea sediments from the Pacific Polymetallic Nodule Province.

A Gram-stain-negative, strictly aerobic, non-motile, rod-shaped, manganese-oxidizing bacterial strain, designated DY6-4T, was isolated from the surface sediment of the Pacific Clarion-Clipperton Fracture Zone. Phylogenetic analysis, based on 16S rRNA gene sequences, indicated that strain DY6-4T formed a lineage within the family Rhodobacteraceae and was distinct from the most closely related genera Sulfitobacter, Aliiroseovarius and Loktanella (94.0-96.0 %, 93.4-96.0 % and 91.9-95.9 % 16S rRNA gene sequence similarity, repectively). Optimal growth occurred in the presence of 1 % (w/v) NaCl, at pH 7.0 and at 28 °C. Strain DY6-4T contained ubiquinone-10 (Q-10) as the major ubiquinone, phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine and one unidentified aminolipid as the predominant polar lipids, C18 : 1ω7c and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) as the main fatty acids (>10 % of the total). The DNA G+C content of strain DY6-4T was 66.6 mol%. On the basis of the polyphasic analyses, strain DY6-4T is considered to represent a novel species of a novel genus in the Roseobacter clade of the family Rhodobacteraceae, for which the name Xuhuaishuia manganoxidans gen. nov., sp. nov. is proposed. The type strain is DY6-4T ( = KCTC 42421T = MCCC 1K00502T).

MomL, a novel marine-derived N-acyl homoserine lactonase from Muricauda olearia.

Gram-negative bacteria use N-acyl homoserine lactones (AHLs) as quorum sensing (QS) signaling molecules for interspecies communication, and AHL-dependent QS is related with virulence factor production in many bacterial pathogens. Quorum quenching, the enzymatic degradation of the signaling molecule, would attenuate virulence rather than kill the pathogens, and thereby reduce the potential for evolution of drug resistance. In a previous study, we showed that Muricauda olearia Th120, belonging to the class Flavobacteriia, has strong AHL degradative activity. In this study, an AHL lactonase (designated MomL), which could degrade both short- and long-chain AHLs with or without a substitution of oxo-group at the C-3 position, was identified from Th120. Liquid chromatography-mass spectrometry analysis demonstrated that MomL functions as an AHL lactonase catalyzing AHL degradation through lactone hydrolysis. MomL is an AHL lactonase belonging to the metallo-ß-lactamase superfamily that harbors an N-terminal signal peptide. The overall catalytic efficiency of MomL for C6-HSL is ∼2.9 × 10(5) s(-1) M(-1). Metal analysis and site-directed mutagenesis showed that, compared to AiiA, MomL has a different metal-binding capability and requires the histidine and aspartic acid residues for activity, while it shares the "HXHXDH" motif with other AHL lactonases belonging to the metallo-ß-lactamase superfamily. This suggests that MomL is a representative of a novel type of secretory AHL lactonase. Furthermore, MomL significantly attenuated the virulence of Pseudomonas aeruginosa in a Caenorhabditis elegans infection model, which suggests that MomL has the potential to be used as a therapeutic agent.

Salipiger nanhaiensis sp. nov., a bacterium isolated from deep sea water.

A Gram-stain-negative, facultatively anaerobic, chemoheterotrophic, moderately halophilic, exopolysaccharide (EPS)-producing, cream, non-motile and rod-shaped bacterium, designated strain ZH114(T), was isolated from deep water of the South China Sea, and was subjected to a polyphasic taxonomic study. Phylogenetic analysis, based on 16S rRNA gene sequences, indicated that this strain belongs to the genus Salipiger with the highest sequence similarity to Salipiger mucescens LMG 22090(T) (96.83%), followed by Pseudodonghicola xiamenensis LMG 24574(T) (96.12%). Growth occurred at 4-37 °C (optimum 32 °C), pH 6.0-10.0 (optimum pH 9.0-10.0) and in the presence of 0-19% NaCl (w/v) (optimum 6%, w/v). It did not produce poly-ß-hydroxyalkanoate granules or bacteriochlorophyll a. Acid was produced from glycerol, erythrose, ribose, D-xylose, galactose, glucose, fructose, mannitol, cellobiose, maltose, lactose, melibiose, turanose, D-lyxose, D-tagatose, D-fucose, D-arabitol and L-arabitol after inoculating for 24 h and weakly positive results were also detected after 48 h in API 50CH strips with D-arabinose, L-arabinose, L-xylose, adonitol, mannose, aesculin, salicin, sucrose, mycose and L-fucose. The predominant fatty acids were C(18 : 1)ω7c and/or C(18 : 1)ω6c, C(16 : 0), C(18 : 0) and 11-methyl C(18 : 1)ω7c. The major polar lipids of ZH114(T) were phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and two unidentified lipids. The major respiratory quinone was ubiquinone Q-10. The genomic DNA G+C content of strain ZH114(T) was 63.8 mol%. Based on this phenotypic, chemotaxonomic and phylogenetic analysis, strain ZH114(T) should be classified as a representative of a novel species of the genus Salipiger , for which the name Salipiger nanhaiensis sp. nov. is proposed. The type strain is ZH114(T) ( = JCM 19383(T) = KCTC 32468(T)).

Description of Thalassotalea piscium gen. nov., sp. nov., isolated from flounder (Paralichthys olivaceus), reclassification of four species of the genus Thalassomonas as members of the genus Thalassotalea gen. nov. and emended description of the genus Thalassomonas.

A Gram-staining-negative, aerobic, rod-shaped bacterium, designated strain T202(T), was isolated from the gill of a cultured flounder (Paralichthys olivaceus). Based on 16S rRNA gene sequence similarity, strain T202(T) was a member of the family Colwelliaceae and shared 93.32-96.58 % similarity with type strains of all members of the most closely related genus Thalassomonas. Phylogenetically, the isolate shared a root with the type strains of four marine species, Thalassomonas agariperforans M-M1(T), Thalassomonas agarivorans TMA1(T), Thalassomonas loyana CBMAI 722(T) and Thalassomonas ganghwensis JC2041(T). Optimal growth occurred in the presence of 2-4 % (w/v) NaCl, at pH 7.0-8.0 and at 28 °C. Ubiquinone 8 (Q-8) was the predominant respiratory quinone. The major fatty acids were C16 : 0, summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), C16 : 1ω9c and C17 : 1ω8c. The major polar lipids were phosphatidylethanolamine and phosphatidylglycerol. The DNA G+C content of strain T202(T) was 37 mol%. On the basis of polyphasic analysis, especially the phylogenetic relationships and the lower DNA G+C content, strain T202(T) is considered to represent a novel species in a new genus, for which the name Thalassotalea piscium gen. nov., sp. nov. is proposed. The type strain of Thalassotalea piscium is T202(T) ( = JCM 18590(T) = DSM 26287(T) = KCTC 32144(T)). Because Thalassomonas agariperforans M-M1(T), Thalassomonas agarivorans TMA1(T), Thalassomonas loyana CBMAI 722(T) and Thalassomonas ganghwensis JC2041(T) formed a phylogenetic group together with strain T202(T) that was clearly separated from other known strains of Thalassomonas, these four species are reclassified as members of the genus Thalassotalea as Thalassotalea agariperforans comb. nov. (type strain M-M1(T) = KCTC 23343(T) = CCUG 60020(T)), Thalassotalea agarivorans comb. nov. (type strain TMA1(T) = BCRC 17492(T) = JCM 13379(T) = DSM 19706(T)), Thalassotalea loyana comb. nov. (type strain CBMAI 722(T) = LMG 22536(T)) and Thalassotalea ganghwensis comb. nov. (type strain JC2041(T) = IMSNU 14005(T) = KCTC 12041(T) = DSM 15355(T)). The type species of the genus Thalassotalea is Thalassotalea ganghwensis gen. nov., comb. nov. An emended description of the genus Thalassomonas is also proposed.

Roseivivax marinus sp. nov., isolated from deep water.

A Gram-stain-negative, strictly aerobic, non-motile, cream, long rod-shaped bacterium, designated strain ZL136(T), was isolated from deep water of the South China Sea. Phylogenetic analysis based on 16S rRNA gene sequences indicated that this strain belonged to the genus Roseivivax with highest sequence similarity to Roseivivax halodurans OCh 239(T) (97.0%), followed by Roseivivax isoporae sw-2(T) (96.9%). Growth occurred at 4-37 °C (optimum 32 °C), pH 6.0-10.0 (optimum 8.0) and in the presence of 0-12% (w/v) NaCl (optimum 3-4%) in marine broth 2216. Strain ZL136(T) did not produce bacteriochlorophyll a. The predominant fatty acids were C(18 : 1)ω7c and/or C(18 : 1)ω6c, C(18 : 0), C(16 : 0) and 11-methyl C(18 : 1)ω7c. The major polar lipids of ZL136(T) were phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and an unidentified lipid. The major respiratory quinone was ubiquinone Q-10. The genomic DNA G+C content of strain ZL136(T) was 67.0 mol%. On the basis of phenotypic, chemotaxonomic and phylogenetic analysis, strain ZL136(T) was classified as a representative of a novel species in the genus of Roseivivax, for which the name Roseivivax marinus sp. nov. is proposed. The type strain is ZL136(T) ( = JCM 19386(T) = KCTC 32470(T)).

Aquimarina megaterium sp. nov., isolated from seawater.

A novel Gram-stain-negative, rod-shaped, non-flagellated, strictly aerobic strain with gliding motility, designated XH134(T), was isolated from surface seawater of the South Pacific Gyre (45° 58' S 163° 11' W) during the Integrated Ocean Drilling Program Expedition 329. The major respiratory quinone of strain XH134(T) was MK-6. The dominant fatty acids of strain XH134(T) were iso-C15 : 0, iso-C15 : 1 G, C16 : 1ω6c and/or C16 : 1ω7c, iso-C17 : 0 3-OH, iso-C15 : 0 3-OH and 10-methyl C16 : 0 and/or iso-C17 : 1ω9c. The polar lipids of strain XH134(T) comprised phosphatidylethanolamine, one unknown aminolipid and three unknown polar lipids. The DNA G+C content of strain XH134(T) was 32.4 mol%. Phylogenetic analyses based on 16S rRNA gene sequences showed that the novel strain was related most closely to Aquimarina macrocephali JAMB N27(T) with 96.9 % sequence similarity. A number of phenotypic characteristics distinguished strain XH134(T) from described members of the genus Aquimarina. On the basis of combined phenotypic and phylogenetic analyses, strain XH134(T) represents a novel species of the genus Aquimarina, for which the name Aquimarina megaterium sp. nov. is proposed. The type strain is XH134(T) ( = CGMCC 1.12186(T) = JCM 18215(T)).

Overexpression and characterization of a novel thermostable ß-agarase YM01-3, from marine bacterium Catenovulum agarivorans YM01(T).

Genome sequencing of Catenovulum agarivorans YM01T reveals 15 open-reading frames (ORFs) encoding various agarases. In this study, extracellular proteins of YM01T were precipitated by ammonium sulfate and separated by one-dimensional gel electrophoresis. The results of in-gel agarase activity assay and mass spectrometry analysis revealed that the protein, YM01-3, was an agarase with the most evident agarolytic activity. Agarase YM01-3, encoded by the YM01-3 gene, consisted of 420 amino acids with a calculated molecular mass of 46.9 kDa and contained a glycoside hydrolase family 16 ß-agarase module followed by a RICIN superfamily in the C-terminal region. The YM01-3 gene was cloned and expressed in Escherichia coli. The recombinant agarase, YM01-3, showed optimum activity at pH 6.0 and 60 °C and had a K(m) of 3.78 mg mL⁻¹ for agarose and a Vmax of 1.14 × 104 U mg⁻¹. YM01-3 hydrolyzed the ß-1,4-glycosidic linkages of agarose, yielding neoagarotetraose and neoagarohexaose as the main products. Notably, YM01-3 was stable below 50 °C and retained 13% activity after incubation at 80 °C for 1 h, characteristics much different from other agarases. The present study highlights a thermostable agarase with great potential application value in industrial production.

Pseudidiomarina fusca sp. nov., Isolated from the Surface Seawater of the Western Pacific Ocean.

The Gram-negative marine bacterium GXY010T, which has been isolated from the surface seawater of the western Pacific Ocean, is aerobic, non-motile and non-flagellated. Strain GXY010T exhibits growth across a temperature range of 10-42 °C (optimal at 37 °C), pH tolerance from 7.0 to 11.0 (optimal at 7.5) and a NaCl concentration ranging from 1.0 to 15.0% (w/v, optimal at 5.0%). Ubiquinone-8 (Q-8) was the predominant isoprenoid quinone in strain GXY010T. The dominant fatty acids (>10%) of strain GXY010T were iso-C15:0 (14.65%), summed feature 9 (iso-C17:1ω9c and/or 10-methyl C16:0) (12.41%), iso-C17:0 (10.85%) and summed feature 3 (C16:1ω7c and/or C16:1ω6c) (10.41%). Phosphatidylethanolamine (PE), phosphatidylglycerol (PG), diphosphatidylglycerol (DPG), unidentifiable glycolipid (GL) and four non-identifiable aminolipids (AL1-AL4) were the predominant polar lipids of strain GXY010T. The genomic DNA G+C content was identified as a result of 48.0% for strain GXY010T. The strain GXY010T genome consisted of 2,766,857 bp, with 2664 Open Reading Frames (ORFs), including 2586 Coding sequences (CDSs) and 78 RNAs. Strain GXY010T showed Average Nucleotide Identity (ANI) values of 73.4% and 70.6% and DNA-DNA hybridization (DDH) values of 19.2% and 14.5% with reference species Pseudidiomarina tainanensis MCCC 1A02633T (=PIN1T) and Pseudidiomarina taiwanensis MCCC 1A00163T (=PIT1T). From the results of the polyphasic analysis, a newly named species, Pseudidiomarina fusca sp. nov. within the genus Pseudidiomarina, was proposed. The type strain of Pseudidiomarina fusca is GXY010T (=JCM 35760T = MCCC M28199T = KCTC 92693T).

Stable microbial community diversity across large-scale Antarctic water masses.

The distinctive environmental attributes of the Southern Ocean underscore the indispensability of microorganisms in this region. We analyzed 208 samples obtained from four separate layers (Surface, Deep Chlorophyll Maximum, Middle, and Bottom) in the neighboring seas of the Antarctic Peninsula and the Cosmonaut Sea to explore variations in microbial composition, interactions and community assembly processes. The results demonstrated noteworthy distinctions in alpha and beta diversity across diverse communities, with the increase in water depth, a gradual rise in community diversity was observed. In particular, the co-occurrence network analysis exposed pronounced microbial interactions within the same water mass, which are notably stronger than those observed between different water masses. Co-occurrence network complexity was higher in the surface water mass than in the bottom water mass. Yet, the surface water mass exhibited greater network stability. Moreover, in the phylogenetic-based ß-nearest taxon distance analyses, deterministic processes were identified as the primary factors influencing community assembly in Antarctic microorganisms. This study contributes to exploring diversity and assembly processes under the complex hydrological conditions of Antarctica.