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.