Aquibacter zeaxanthinifaciens gen. nov., sp. nov., a zeaxanthin-producing bacterium of the family Flavobacteriaceae isolated from surface seawater, and emended descriptions of the genera Aestuariibaculum and Gaetbulibacter.

A Gram-stain-negative, strictly aerobic, rod-shaped, non-flagellated, non-spore-forming and gliding marine bacterium, designated strain CC-AMZ-304(T), was isolated from coastal surface seawater near Taichung harbour, Taiwan. Strain CC-AMZ-304(T) predominantly synthesized zeaxanthin and thus formed yellow colonies on marine agar. The novel strain showed an unstable phylogenetic position, although sharing high pairwise 16S rRNA gene sequence similarities of 95.9-94.9, 95.7 and 95.1-93.9 % with Gaetbulibacter species (n = 4), Aestuariibaculum suncheonense SC17(T) and Bizionia species (n = 7), respectively. The polar lipid profile of strain CC-AMZ-304(T) consisted of phosphatidylethanolamine, five unidentified lipids, one unidentified phospholipid, two unidentified aminolipids and one unidentified glycolipid. The major (>5 % of the total) fatty acids were iso-C15 : 0, iso-C15 : 1 G, iso-C17 : 0 3-OH, iso-C15 : 0 3-OH and C15 : 1ω5c. The DNA G+C content was 36.0 mol%. Menaquinone-6 (MK-6) was the sole respiratory quinone and the major polyamine was triamine sym-homospermidine. Phylogenetic distinctiveness, unique polar lipid composition, presence of significant amounts of branched hydroxyl fatty acids (iso-C17 : 0 3-OH and iso-C15 : 0 3-OH) and a low amount of anteiso-C15 : 0, and several additional distinguishing biochemical features clearly discriminated strain CC-AMZ-304(T) from the type species of the genera Aestuariibaculum and Gaetbulibacter. Thus, based on data from the present polyphasic study, strain CC-AMZ-304(T) is considered to represent a novel species of a new genus within the family Flavobacteriaceae, for which the name Aquibacter zeaxanthinifaciens gen. nov., sp. nov. is proposed; the type strain of Aquibacter zeaxanthinifaciens is CC-AMZ-304(T) ( = JCM 18557(T) = BCRC 80463(T)). Emended descriptions of the genera Aestuariibaculum and Gaetbulibacter are also proposed.