Thioclava litoralis sp. nov., a novel species of alphaproteobacterium, isolated from surface seawater.

A Gram-negative, aerobic, rod-shaped, non-motile bacterium, designated as FTW29^T, was isolated from surface seawater sampled in Futian district, Shenzhen, China. Growth of strain FTW29^T was observed at 15-42 ℃ (optimum, 28-30 ℃), pH 4.0-9.0 (optimum, pH 5.5-7.5) and in the presence of 0.5-10% NaCl (optimum, 3.0% NaCl). Strain FTW29^T showed 95.0-96.8% 16 S rRNA gene sequence similarity to various type strains of the genera Thioclava, Sinirhodobacter, Rhodobacter, Haematobacter and Frigidibacter of the family Paracoccaceae, and its most closely related strains were Thioclava pacifica DSM 10,166^T (96.8%) and Thioclava marina 11.10-0-13^T (96.7%). The phylogenomic tree constructed on the bac120 gene set showed that strain FTW29^T formed a clade with the genus Thioclava, with a bootstrap value of 100%. The evolutionary distance values between FTW29^T and type strains of the genus Thioclava were 0.17-0.19, which are below the recommended standard (0.21-0.23) for defining a novel genus in the family Paracoccaceae. In strain FTW29^T, the major fatty acids identified were summed feature 8 (C_18:1ω7c) and C_16:0, and the predominant respiratory quinones were ubiquinone-10 and ubiquinone-9. The composition of polar lipids in strain FTW29^T included diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, an unidentified phospholipid, an unidentified aminolipid, two unidentified glycolipids and an unidentified lipid. The genome of strain FTW29^T comprised one circle chromosome and six plasmids, with a G + C content of 61.4%. The average nucleotide identity, average amino acid identity, and digital DNA-DNA hybridization values between strain FTW29^T and seven type strains of the genus Thioclava were 76.6-78.4%, 53.2-56.4% and 19.3-20.4%, respectively. Altogether, the phenotypic, phylogenetic and chemotaxonomic evidence illustrated in this study suggested that strain FTW29^T represents a novel species of the genus Thioclava, with the proposed name Thioclava litoralis sp. nov. The type strain is FTW29^T (= KCTC 82,841^T = MCCC 1K08523^T).