Hyphococcus flavus gen. nov., sp. nov., a novel alphaproteobacterium isolated from deep seawater

A Gram-staining-negative, aerobic, non-spore-forming, coccoid to rod shaped bacteria with prosthecate and flagellum, designated as HSF6^T, was isolated from deep seawater samples collected from the South China Sea at depth of 2.5 km and subjected to a polyphasic taxonomic investigation. Colonies of strain HSF6^T were 1-2 mm in diameter, smooth, circular, convex and yellow. Strain HSF6^T was found to grow at 15-37 °C (optimum, 25-35 °C), pH 5.0-9.5 (optimum, pH 7.0-7.5) and with 0-8 % (w/v) NaCl (optimum, 2 %). Chemotaxonomic analysis showed the predominant respiratory quinone of strains HSF6^T were ubiquinone-10, and the major fatty acids were C18 : 1ω7c, C16 : 0 and 11-methyl C18 : 1ω7c. The polar lipids were monoglycosyldiglyceride (MGDG), sulfo-quinovosyl diacylglycerol (SQDG), three unknown glycolipids (GL1-3) and five unknown lipids (L1-5). The DNA G+C content of strain HSF6^T was determined to be 51.0 mol% with HPLC. The comparison of 16S rRNA gene sequence similarities show that strain HSF6^T was related most closely to genus Parvularcula with similarity ranging from 91.0 to 91.8 %. The phylogenetic trees, using the 16S rRNA gene sequence, reconstructed with neighbour-joining, maximum-parsimony and maximum-likelihood methods showed that strain HSF6^T constituted a separated branch in the family 'Parvularculaceae'. Differential phenotypic properties, together with the phylogenetic distinctiveness, demonstrated that strain HSF6^T is clearly distinct from validly published genera. On the basis of these features, we propose strain HSF6^T (=MCCC 1K03223^T=KCTC 52486^T) represents a novel species of a novel genus with the name Hyphococcus flavus gen. nov., sp. nov.