Algibacter onchidii sp. nov., a symbiotic bacterium isolated from a marine invertebrate

A novel symbiotic bacterium, designated strain XY-114^T, was isolated from the cerata of an Onchidium marine invertebrate species collected in the South China Sea. Strain XY-114^T was an aerobic, Gram-stain-negative, non-motile and short rod-shaped bacterium (0.5-0.8 µm wide and 1.0-1.5 µm long) without flagellum. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain XY-114^T belonged to the genus Algibacter with the highest similarity of 97.2 % to the closest phylogenetic relative Algibacter aestuarii KYW371^T. Cells grew at 15-37 °C (optimum, 30 °C), at pH 5.5-9.0 (optimum 7.0-8.0) and at NaCl concentrations of 0.5-5.0 % (w/v; optimum 1.5-3.0 %). The major fatty acids (>10 %) were summed feature 3 (comprising C_16 : 1  ω7c and/or C_16 : 1  ω6c), iso-C_15 : 0, iso-C_15 : 1 G and iso-C_17 : 0 3-OH. The predominant polar lipid was phosphatidylethanolamine. The predominant respiratory quinone was MK-6. Flexirubin-type pigments were absent. The genome size of strain XY-114^T was 3.4 Mbp, with 34.9 mol% of DNA G+C content. The average nucleotide identity, digital DNA-DNA hybridization and amino acid identity values between strain XY-114^T and A. aestuarii KYW371^T were 74.5 %, 17.0±1.8 % and 73.9 %. Characterization based on phylogenetic, phenotypic, chemotaxonomic and genomic evidence demonstrated that strain XY-114^T represents a novel species of the genus Algibacter, for which the name Algibacter onchidii sp. nov. is proposed. The type strain is XY-114^T (=KCTC 72217^T=MCCC 1K03606^T).