Sphingomicrobium astaxanthinifaciens sp. nov., an astaxanthin-producing glycolipid-rich bacterium isolated from surface seawater and emended description of the genus Sphingomicrobium

Abstract

A Gram-stain-negative, rod-shaped, strictly aerobic, flagellated and non-spore-forming marine bacterium designated strain CC-AMO-30BT was isolated from coastal surface seawater, Taiwan. Strain CC-AMO-30BT synthesized astaxanthin [40 µg (g dry weight)−1] and formed reddish-orange-coloured colonies on marine agar (Difco 2216). The strain showed highest pairwise 16S rRNA gene sequence similarity to Sphingomicrobium lutaoense CC-TBT-3T (96.4 %) followed by other members of the family Sphingomonadaceae (<94 %) and established a discrete phyletic lineage associated with the former. The polar lipid profile constituted a remarkable number of unidentified glycolipids (GL1–8), in addition to diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, sphingoglycolipid and two unidentified lipids (L1–2). The major fatty acids (>5 % of total fatty acids) were C18 : 1ω7c/C18 : 1ω6c (summed feature 8), C16 : 1ω7c/C16 : 1ω6c (summed feature 3), C18 : 1 2-OH, methyl C18 : 1ω7c, C17 : 1ω6c and C16 : 0. DNA G+C content was 70.6 %; major respiratory quinone was ubiquinone Q-10; predominant polyamine was the triamine sym-homospermidine. Chemotaxonomic evidence including characteristic glycolipid profile, presence of significant amounts of C18 : 1 2-OH and absence of typical hydroxylated fatty acids such as C14 : 0 2-OH, C15 : 0 2-OH and C16 : 0 2-OH in considerable amounts, accompanied by phylogenetic distinctiveness and several other phenotypic features support the classification of strain CC-AMO-30BT as a representative of a novel species within the genus Sphingomicrobium for which the name Sphingomicrobium astaxanthinifaciens sp. nov. is proposed; the type strain is CC-AMO-30BT ( = JCM 18551T = BCRC 80465T).