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

A novel bacterial strain, A3T, 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 A3T 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 (C_16 : 1ω7c and/or C_16 : 1ω6c) and C_16 : 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 A3T and its closest relatives in the genus Colwellia ( C. psychrerythraea ATCC 27364T and C. asteriadis KMD 002T) was 97.5 %. The average nucleotide identity between strain A3T and other members of Colwellia was 78.6–80.5 %, and DNA–DNA hybridization prediction revealed values of less than 23 % relatedness between strain A3T and other Colwellia species. The phenotypic, phylogenetic and genomic analyses support the hypothesis that strain A3T represents a novel species of the genus Colwellia , for which the name Colwellia echini sp. nov. is proposed. The type strain is A3T (=LMG 30125T=NCIMB 15095T).