Mesobacterium hydrothermale sp. nov., isolated from shallow-sea hydrothermal systems off Kueishantao Island.

A Gram-negative, rod-shaped, non-motile, aerobic bacterium, designated as strain TK19101T, was isolated from the intermediate seawater of yellow vent in the shallow-sea hydrothermal system located near Kueishantao Island. The strain was found to grow at 10-40 °C (optimum, 35 °C), at pH 6.0-8.0 (optimum, 7.0), and in 0-5% (w/v) NaCl (optimum, 1%). Strain TK19101T was catalase-positive and oxidase-positive. The predominant fatty acids (> 10%) in strain TK19101T cells were C16:0, summed feature 8 (C18:1 ω6c and/or C18:1 ω7c), and C18:0. The predominant isoprenoid quinone of strain TK19101T was ubiquinone-10. The polar lipids of strain TK19101T comprised phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, phospholipid, and unknown polar lipid. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain TK19101T belonged to the genus Mesobacterium. Strain TK19101T exhibited highest 16S rRNA gene sequence similarity value to Mesobacterium pallidum MCCC M24557T (97.48%). The estimated average nucleotide identity and digital DNA-DNA hybridization values between strain TK19101T and the closest related species Mesobacterium pallidum MCCC M24557T were 74.88% and 20.30%, respectively. The DNA G + C content was 63.49 mol%. On the basis of the analysis of 16S rRNA gene sequences, genotypic and phylogenetic data, strain TK19101T has a unique phylogenetic status and represents a novel species of genus Mesobacterium, for which the name Mesobacterium hydrothermale sp. nov. is proposed. The type strain is TK19101T (= MCCC 1K08936T = KCTC 8354T).

Roseihalotalea indica gen. nov., sp. nov., a halophilic Bacteroidetes from mesopelagic Southwest Indian Ocean with higher carbohydrate metabolic potential.

The pink-colored and strictly aerobic bacterium strain, designated as TK19036T, was isolated from mesopelagic layer of the Southwest Indian Ocean. This novel isolate can grow at 10-45 °C (optimum, 30 °C), pH 6.0-8.0 (optimum, pH 7.0), and 2-14% NaCl concentrations (w/v) (optimum, 6%). The predominant respiratory quinone was Menaquinone-7. Major polar lipid profiles contained two aminolipids, aminophospholipid, two glycolipids, phosphatidylethanolamine, and three unknown polar lipids. The preponderant cellular fatty acids were iso-C15:0, C16:1 ω5c and iso-C17:0 3-OH. Phylogenetic analyses based on 16S rRNA gene sequence uncovered that the strain TK19036T pertained to the family Catalinimonadaceae under phylum Bacteroidota, and formed a distinct lineage with the closed species Tunicatimonas pelagia NBRC 107804T. The up-to-bacteria-core gene phylogenetic trees also demonstrated a deep and novel branch formed by the strain TK19036T within the family Catalinimonadaceae. Based on chemotaxonomic, phylogenetic and genomic features presented above, strain TK19036T represents a novel species from a novel genus of the family Catalinimonadaceae, for which the name Roseihalotalea indica gen. nov. sp. nov. is proposed. The type strain is TK19036T (= CGMCC 1.18940T = NBRC 116371T).

Thermobacterium salinum gen. nov., sp. nov., a novel member of the family Flavobacteriaceae isolated from a hydrothermal zone.

A Gram-stain-negative, aerobic, non-motile and rod-shaped bacterial strain, designated as strain TK19130T, was isolated from the Lonqi hydrothermal zone in the Southwest Indian Ridge. Growth occurred with 1-12 % (w/v) NaCl (optimum, 2-4 %), at 10-40 °C (optimum, 30-35 °C) and at pH 6.0-9.0 (optimum, pH 7.0-8.0). The genome of strain TK19130T was 3.15 Mb, with a DNA G+C content of 41.35 %. Based on the results of 16S rRNA gene sequence analysis, strain TK19130T was affiliated with the family Flavobacteriaceae, in which the highest similarity was 90.54 % to Aureisphaera salina A6D-50T, under the genus demarcation boundary (94.50 %). Average nucleotide identity values between strain TK19130T and adjacent strains were 67.17-72.00 %, lower than the recommended threshold of 73.98 % for genus delineation. The predominant respiratory quinone of strain TK19130T was menaquinone 6. Major polar lipids were phosphatidylethanolamine, three aminolipids and one unidentified polar lipid. Major fatty acids were detected as iso-C15 : 1 G, iso-C15 : 0 and iso-C17 : 0 3-OH. Based on the polyphasic taxonomic evidence presented above, strain TK19130T formed an independent branch representing a new species of a novel genus within the family Flavobacteriaceae, for which the name Thermobacterium salinum gen. nov., sp. nov. is proposed. The type strain is TK19130T (=CGMCC 1.18993T=JCM 35842T=MCCC M28200T).

Paracoccus albicereus sp. nov., isolated from the shallow-sea hydrothermal system off Kueishantao Island.

Strain designated TK19116T was isolated from the shallow-sea hydrothermal systems off Kueishantao Island in Taiwan, China. The bacterium was Gram-stain-negative, aerobic, oxidase-positive and catalase-positive. Cells of the strain TK19116T were short-rod-shaped and non-motile. The results of phylogenetic analysis of 16S rRNA gene sequences indicated that strain TK19116T belonged to the genus Paracoccus, with the highest sequence similarity to Paracoccus alkanivorans 4-2T (97.1 %). The average nucleotide identity values between the strain TK19116T with Paracoccus alkanivorans 4-2T, Paracoccus zhejiangensis J6T, Paracoccus siganidrum M26T and Paracoccus tegillarcae BM15T were 75.3, 76.7, 76.7 and 75.8%, respectively. The digital DNA-DNA hybridization value between the strain TK19116T with Paracoccus alkanivorans 4-2T, Paracoccus zhejiangensis J6T, Paracoccus siganidrum M26T and Paracoccus tegillarcae BM15T were 19.7, 20.3, 20.5 and 20.0%, respectively. The main respiratory quinone of strain TK19116T was ubiquinone 10. The polar lipids include aminolipid, phosphatidylcholine, diphosphatidylglycerol, glycolipid, phosphatidylglycerol and phospholipid. The principal fatty acid of strain TK19116T was summed feature 8 (C18 : 1 ω6c and/or C18 : 1 ω7c). The G+C content of the chromosomal DNA was 64.2 %. The combination of the results of the phylogenetic, phenotypic and chemotaxonomic analysis, strain TK19116T represents a novel species of the genus Paracoccus, for which the name Paracoccus albicereus sp. nov. is proposed. The type strain is TK19116T (= MCCC 1K08025T=JCM 35527T).

Croceicoccus hydrothermalis sp. nov., isolated from shallow-sea hydrothermal system off Kueishantao Island.

A Gram-stain-negative, strictly aerobic, non-motile, ovoid or short-rod shaped, orange-pigmented bacterial strain, designated as strain JLT1T, was isolated from seawater of the shallow-sea hydrothermal system, near Kueishantao Islet. Growth was observed at 5-45°C (optimum, 30 °C) and pH 5.0-11.0 (optimum, pH 7.0). The salinity range for growth was 0-12 % (optimum, 2-4 %) (w/v) NaCl. JLT1T contained ubiquinone-10 as the main respiratory quinone. Iso-C12 : 0, summed feature 3 (C16 : 1ω7c/ω6c) and summed feature 8 (C18 : 1ω6c/ω7c) were identified as the major cellular fatty acids. Polar lipids included diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, three unidentified phospholipids, eight unidentified glycolipids and an unidentified lipid. The 16S rRNA gene of JLT1T shared the greatest similarity (96.31 %) with those of Croceicoccus pelagius Ery9T and Croceicoccus ponticola GM-16T. The draft genome size of JLT1T is 3.56 Mb, with 3578 potential genes and a genomic DNA G+C content of 63.24 mol %. Average nucleotide identity and digital DNA-DNA hybridization values of JLT1T compared with C. pelagius Ery9T, C. ponticola GM-16T, Croceicoccus sediminis S2-4-2T, Croceicoccus mobilis Ery22T and Croceicoccus marinus E4A9T were 74.5, 73.9, 74.4, 74.3 and 74.8 % and 20.6, 19.2, 20.0, 20.5 and 19.8%, respectively. On the basis of these phylogenetic, chemotaxonomic and phenotypic features, JLT1T is concluded to represent a novel species of the genus Croceicoccus, for which the name Croceicoccus hydrothermalis sp. nov. is proposed. The type strain is JLT1T (=CGMCC 1.15786T =JCM 31508T).

Roseovarius carneus sp. nov., a novel bacterium isolated from a coastal phytoplankton bloom in Xiamen.

A Gram-stain-negative, non-motile, ovoid or short rod shaped and aerobic marine bacterium, designated as strain LXJ103T, was isolated from a coastal phytoplankton bloom in Xiamen, PR China. Cells were oxidase- and catalase-positive. Strain LXJ103T grew at 4-40 °C (optimum, 28-37 °C), at pH 6-10 (optimum, pH 8.5) and with 1-15 % (w/v) NaCl (optimum, 3 %). The major cellular fatty acids (>10 %) were iso-C18 : 1 ω7c/iso-C18 : 1 ω6c (70.2 %) and C16 : 0 (10.3 %). The following polar lipids were found to be present: phosphatidylglycerol, phosphatidylethanolamine, two unidentified phospholipids and five unknown glycolipids. The predominant respiratory quinone was ubiquinone-10. Strain LXJ103T exhibited the highest 16S rRNA gene sequence similarity to Roseovarius litorisediminis D1-W8T (96.97 %). The phylogenetic trees based on 16S rRNA gene sequences showed that strain LXJ103T was a member of the genus Roseovarius. The draft genome size of strain LXJ103T is 3.05 Mb with a genomic G+C content of 61.22 mol%. The digital DNA-DNA genome hybridization value of strain LXJ103T compared with the most similar type strain R. litorisediminis CECT 8287T was 18.80 %. The average nucleotide identity value between strain LXJ103T and R. litorisediminis CECT 8287T was 72.60 %. On the basis of polyphasic data, strain LXJ103T represents a novel species of the genus Roseovarius, for which the name Roseovarius carneus sp. nov. is proposed. The type strain is LXJ103T (=CGMCC 1.19168T=MCCC 1K06527T=JCM 34778T).

Discovery of a novel marine Bacteroidetes with a rich repertoire of carbohydrate-active enzymes.

Members of the phylum Bacteroidetes play a key role in the marine carbon cycle through their degradation of polysaccharides via carbohydrate-active enzymes (CAZymes) and polysaccharide utilization loci (PULs). The discovery of novel CAZymes and PULs is important for our understanding of the marine carbon cycle. In this study, we isolated and identified a potential new genus of the family Catalimonadaceae, in the phylum Bacteroidetes, from the southwest Indian Ocean. Strain TK19036, the type strain of the new genus, is predicted to encode CAZymes that are relatively abundant in marine Bacteroidetes genomes. Tunicatimonas pelagia NBRC 107804T, Porifericola rhodea NBRC 107748T and Catalinimonas niigatensis NBRC 109829T, which exhibit 16 S rRNA similarities exceeding 90% with strain TK19036, and belong to the same family, were selected as reference strains. These organisms possess a highly diverse repertoire of CAZymes and PULs, which may enable them to degrade a wide range of polysaccharides, especially pectin and alginate. In addition, some secretory CAZymes in strain TK19036 and its relatives were predicted to be transported by type IX secretion system (T9SS). Further, to the best of our knowledge, we propose the first reported "hybrid" PUL targeting alginates in T. pelagia NBRC 107804T. Our findings provide new insights into the polysaccharide degradation capacity of marine Bacteroidetes, and suggest that T9SS may play a more important role in this process than previously believed.