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).