Colwellia ponticola sp. nov., isolated from seawater

A Gram-stain-negative, aerobic, motile and rod-shaped bacterial strain, designated OISW-25^T, was isolated from seawater in Republic of Korea. Strain OISW-25^T grew optimally at 25 °C and in the presence of 2.0 % (w/v) NaCl. The phylogenetic trees based on 16S rRNA gene sequences showed that strain OISW-25^T fell within the clade comprising the type strains of Colwellia species. Strain OISW-25^T exhibited 16S rRNA gene sequence similarity values of 97.5, 97.2 and 97.1 % to the type strains of C. piezophila, C. maris and C. psychrerythraea, respectively, and of 93.6-96.6 % to the type strains of the other Colwellia species. The average nucleotide identity values between strain OISW-25^T and C. piezophila ATCC BAA-637^T and two non-type strains of C. psychrerythraea were 78.16-79.35 % and DNA-DNA relatedness value of strain OISW-25^T with the type strain of C. maris was 17 %. The DNA G+C content of strain OISW-25^T was 39.2 mol% (HPLC) or 38.7 mol% (genome data). Strain OISW-25^T contained Q-8 as the predominant ubiquinone and summed feature 3 (C_16 : 1  ω7c and/or C_16 : 1  ω6c) and C_16 : 0 as the major fatty acids. The major polar lipids of strain OISW-25^T were phosphatidylethanolamine and phosphatidylglycerol. Distinguished phenotypic properties, along with the phylogenetic and genetic distinctiveness, revealed that strain OISW-25^T is distinct from Colwellia species. On the basis of the data presented, strain OISW-25^T is considered to represent a novel species of the genus Colwellia, for which the name Colwellia ponticola sp. nov. is proposed. The type strain is OISW-25^T (=KCTC 62426^T=NBRC 113187^T).

Colwellia echini sp. nov., an agar- and carrageenan-solubilizing bacterium isolated from sea urchin

A novel bacterial strain, A3^T, was isolated from the intestines of the sea urchin Strongylocentrotus droebachiensis collected in Øresund, Denmark. The strain was Gram-reaction-negative, rod-shaped and facultatively anaerobic, and displayed growth at 5-25 °C (optimum 20 °C), pH 7-9 (optimum at pH 7) and 1-6 % (w/v) NaCl (optimum 3 %). Furthermore, strain A3^T grew on agar, agarose, κ-carrageenan, alginate and laminarin as sole carbon source. Complete liquefaction of agar and κ-carrageenan was observed on solid plate media as a result of enzymatic activities. Major fatty acids were summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) and C16 : 0. The respiratory quinones were determined to be ubiquinones Q-8 (92 %) and Q-7 (8 %), and polar lipids were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The DNA G+C content was 36.9 mol%. Phylogenetical analyses based on the 16S rRNA gene showed that the bacterium was affiliated with the genus Colwellia within the Alteromonadaceae of the Gammaproteobacteria. The level of 16S rRNA gene sequence similarity between strain A3^T and its closest relatives in the genus Colwellia (C. psychrerythraea ATCC 27364^T and C. asteriadis KMD 002^T) was 97.5 %. The average nucleotide identity between strain A3^T and other members of Colwellia was 78.6-80.5 %, and DNA-DNA hybridization prediction revealed values of less than 23 % relatedness between strain A3^T and other Colwellia species. The phenotypic, phylogenetic and genomic analyses support the hypothesis that strain A3^T represents a novel species of the genus Colwellia, for which the name Colwellia echini sp. nov. is proposed. The type strain is A3^T (=LMG 30125^T=NCIMB 15095^T).

Colwellia mytili sp. nov., isolated from mussel Mytilus edulis

A Gram-stain-negative, aerobic, motile and rod-shaped bacterial strain, designated RA2-7T, was isolated from a mussel (Mytilus edulis) collected from the South Sea, South Korea, and subjected to a taxonomic study using a polyphasic approach. Strain RA2-7T grew optimally at 20 °C, at pH 7.0-8.0 and in the presence of 2.0-3.0 % (w/v) NaCl. The phylogenetic trees based on 16S rRNA gene sequences showed that strain RA2-7T belonged to the genus Colwellia. Strain RA2-7T exhibited 16S rRNA gene sequence similarity values of 98.3, 98.0 and 97.5 % to the type strains of Colwellia sediminilitoris, Colwellia aestuarii and Colwellia polaris, respectively, and of 94.5-96.5 % to the type strains of the other species of the genus Colwellia. Strain RA2-7T contained Q-8 as the predominant ubiquinone and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) and C16 : 0 as the major fatty acids. The major polar lipids detected in strain RA2-7T were phosphatidylglycerol and phosphatidylethanolamine. The DNA G+C content of strain RA2-7T was 39.0±0.04 mol% and its DNA-DNA relatedness values with the type strains of C. sediminilitoris, C. aestuarii and C. polaris were 14-19 %. Differential phenotypic properties, together with its phylogenetic and genetic distinctiveness, revealed that strain RA2-7T is separated from recognized species of the genus Colwellia. On the basis of the data presented, strain RA2-7T is considered to represent a novel species of the genus Colwellia, for which the name Colwellia mytili sp. nov. is proposed. The type strain is RA2-7T (=KCTC 52417T=NBRC 112381T).

Colwellia sediminilitoris sp. nov., isolated from a tidal flat

A Gram-stain-negative, aerobic, motile and rod-shaped or ovoid bacterial strain, designated YSM-23T, was isolated from a tidal flat on the South Sea in South Korea, and subjected to a polyphasic taxonomic study. Strain YSM-23T grew optimally at 30 °C, at pH 7.0-8.0 and in the presence of 1.0-2.0 % (w/v) NaCl. The phylogenetic trees based on 16S rRNA gene sequences showed that strain YSM-23T represented a member of the genus Colwellia. Strain YSM-23T exhibited 16S rRNA gene sequence similarity values of 98.0, 97.4 and 97.3 % to the type strains of Colwellia aestuarii, Colwellia polaris and Colwellia chukchiensis, respectively, and of 94.5-96.8 % to the type strains of the other species of the genus Colwellia. Strain YSM-23T contained Q-8 as the predominant ubiquinone and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) as the major fatty acid. The major polar lipids detected in strain YSM-23T were phosphatidylglycerol and phosphatidylethanolamine. The DNA G+C content of strain YSM-23T was 43.8±0.08 mol% and its DNA-DNA relatedness values with the type strain of C. aestuarii, C. polaris and C. chukchiensis were 10±3.5-22±4.9 %. Differential phenotypic properties, together with its phylogenetic and genetic distinctiveness, revealed that strain YSM-23T is separated from species of the genus Colwelliawith validly published names. On the basis of the data presented, strain YSM-23T is considered to represent a novel species of the genus Colwellia, for which the name Colwellia sediminilitoris sp. nov. is proposed. The type strain is YSM-23T (=KCTC 52213T=NBRC 111994T).

The Cultivable Surface Microbiota of the Brown Alga Ascophyllum nodosum is Enriched in Macroalgal-Polysaccharide-Degrading Bacteria

Bacteria degrading algal polysaccharides are key players in the global carbon cycle and in algal biomass recycling. Yet the water column, which has been studied largely by metagenomic approaches, is poor in such bacteria and their algal-polysaccharide-degrading enzymes. Even more surprisingly, the few published studies on seaweed-associated microbiomes have revealed low abundances of such bacteria and their specific enzymes. However, as macroalgal cell-wall polysaccharides do not accumulate in nature, these bacteria and their unique polysaccharidases must not be that uncommon. We, therefore, looked at the polysaccharide-degrading activity of the cultivable bacterial subpopulation associated with Ascophyllum nodosum. From A. nodosum triplicates, 324 bacteria were isolated and taxonomically identified. Out of these isolates, 78 (~25%) were found to act on at least one tested algal polysaccharide (agar, ι- or κ-carrageenan, or alginate). The isolates “active” on algal-polysaccharides belong to 11 genera: Cellulophaga, Maribacter, Algibacter, and Zobellia in the class Flavobacteriia (41) and Pseudoalteromonas, Vibrio, Cobetia, Shewanella, Colwellia, Marinomonas, and Paraglaceciola in the class Gammaproteobacteria (37). A major part represents likely novel species. Different proportions of bacterial phyla and classes were observed between the isolated cultivable subpopulation and the total microbial community previously identified on other brown algae. Here, Bacteroidetes and Gammaproteobacteria were found to be the most abundant and some phyla (as Planctomycetes and Cyanobacteria) frequently encountered on brown algae weren't identified. At a lower taxonomic level, twelve genera, well-known to be associated with algae (with the exception for Colwellia), were consistently found on all three A. nosodum samples. Even more interesting, 9 of the 11 above mentioned genera containing polysaccharolytic isolates were predominant in this common core. The cultivable fraction of the bacterial community associated with A. nodosum is, thus, significantly enriched in macroalgal-polysaccharide-degrading bacteria and these bacteria seem important for the seaweed holobiont even though they are under-represented in alga-associated microbiome studies.