Sphingomicrobium marinum sp. nov. and Sphingomicrobium flavum sp. nov., isolated from surface seawater, and emended description of the genus Sphingomicrobium

Abstract

Two Gram-staining-negative, yellow-pigmented, rod-shaped, strictly aerobic, non-flagellated and non-spore-forming amylolytic marine bacterial strains, designated CC-AMZ-30MT and CC-AMZ-30NT, were isolated from coastal surface seawater in Taiwan. Strain CC-AMZ-30MT shared pairwise 16S rRNA gene sequence similarities of 95.8, 95.0 and <94.0 % to Sphingomicrobium lutaoense CC-TBT-3T, Sphingomicrobium astaxanthinifaciens CC-AMO-30BT and other sphingomonads, respectively. Strain CC-AMZ-30NT shared 97.0, 96.7, 95.0 and <95.1 % similarities to strain CC-AMZ-30MT, Sphingomicrobium lutaoense CC-TBT-3T, Sphingomicrobium astaxanthinifaciens CC-AMO-30BT and other sphingomonads, respectively. The common polar lipids of the two strains include a signature glycolipid (GL2), diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and sphingoglycolipid in major amounts besides moderate-to-trace amounts of an unidentified aminolipid and several unidentified glycolipids. Both strains contained C18 : 1ω7c/C18 : 1ω6c, C16 : 1ω7c/C16 : 1ω6c, C16 : 0 and C18 : 1 2-OH as major (>5 % of the total) fatty acids. Strains CC-AMZ-30MT and CC-AMZ-30NT had DNA G+C contents of 64.2 and 65.2 mol%, respectively. The major polyamine was spermidine in strain CC-AMZ-30MT and triamine sym-homospermidine in strain CC-AMZ-30NT. Both strains contained ubiquinone Q-10 as the predominant respiratory quinone. Differential phylogenetic and chemotaxonomic evidence including the presence of characteristic GL2, C18 : 1 2-OH and several other phenotypic features supported the classification of strains CC-AMZ-30MT and CC-AMZ-30NT as two novel species of the genus Sphingomicrobium , for which we propose the names Sphingomicrobium marinum sp. nov. and Sphingomicrobium flavum sp. nov., respectively; corresponding type strains are Sphingomicrobium marinum CC-AMZ-30MT ( = JCM 18554T = BCRC 80466T) and Sphingomicrobium flavum CC-AMZ-30NT ( = JCM 18555T = BCRC 80467T). An emended description of the genus Sphingomicrobium is also proposed.