Polyphasic Taxonomy Of Two Bacterial Strains From The Pacific Seawater

The Pacific Ocean, the largest and the deepest ocean of the Earth, covers49.8%of the total oceans’surface area, containing huge numbers of marine microorganisms with tremendous diversities. These microorganisms have evolved unique physiological and metabolic characteristics and play important ecological role in marine ecosystems.. Isolation and identification of these marine microorganisms are the initial and important steps for further research and exploitations of them. In this study, two novel strains were isolated from seawater samples of the Pacific Ocean and were taxonomically characterized by using polyphasic methods, including morphological observations, examinations of growth conditions, tests for physiological properties and biochemical properties, determination of cellular fatty acid and polar lipid compositions, analysis of molecular genetics analysis. Based on the polyphasic data obtained in this study, the two strains’exact taxonomic positions were finally determined.1. Polyphasic taxonomic study of strain P-50-3Strain P-50-3was isolated from a water sample at the depth of50m at the CTD04site of the Pacific Ocean. Cells of the type strain are Gram-negative and rods. The type strain grew at10-40℃(optimum at30℃), in0-12%NaCl (w/v, optimum in2.0%) and at pH6.0-9.5(optimum at pH7.5). Cells were Oxidase-and Catalyse-positive. It reduced nitrate to nitrite but did not hydrolyze gelatin, casein, elastin, starch, Tween80or esculin.The major respiratory quinone was Q-10and the major cellular fatty acids were C18:1ω7c, C18:0,11-methyl C18:1ω7c and Ci6:o. Polar lipids included phosphatidylglycerol (PG), phosphatidylcholine (PC), two unidentified aminolipids and an unidentified lipid. The genomic G+C content of the type strain was69.0mol%.Analysis of16S rRNAgene sequences showed that strain P-50-3shared the highest16S rRNA gene sequence similarity (94.3%) with type strain of Albimonas donghaensis. In the neighbour-joining tree based on16S rRNA gene sequence, strain P-50-3, together with Albimonas donghaensis DS2T, formed a distinct branch in the family Rhodobacteraceae.Based on the polyphasic taxonomic data, Albimonas pacifica P-50-3represents a novel species within the genus Albimonas, for which the name Albimonas pacifica sp. nov. is proposed. The type strain of Albimonas pacifica is P-50-3T (=KACC16527T=CGMCC1.11030T).2. Polyphasic taxonomic study of strain P-lkm-3Strain P-1km-3was isolated from a seawater sample collected from the water depth of1000m at the CTD04site of the Pacific Ocean. Cells of strain P-1km-3were Gram-negative, strictly aerobic, dimorphic rods with a single polar prostheca or flagellum. Cells of the type strain are1.0-3.0μm in length and0.3-0.5μm in width. The strain grew at6-40°C (optimum at30°C), in0.5-12%NaCl (w/v, optimum in2.0%) and at pH6.0-9.5(optimum at pH7.0).The predominant fatty acids of strain P-1km-3included C18:1ω7c, C18:0,11-methyl C18:1ω7c, C17:0and C19:0cyclo ω8c Polar lipids of the strain were mainly composed of glucuronopyranosyldiglyceride (GUDG), mono-glycosyldiglyceride (MGDG), sulfo-quinovosyl diacylglycerol (SQDG) and phosphatidylglycerol (PG). The genomic G+C content of strain P-lkm-3was66.0mol%.The strain displayed the highest16S rRNA gene sequence similarities with type strains of Oceanicaulis alexandrii (93.5%) and Maricanlis parjimensis (93.2%), followed by Woodsholea maritima (93.2%). In the neighbour-joining tree, strain P-lkm-3formed a distinct phylogenetic branch within the cluster of the family HyphomonadaceaeOn the basis of the polyphasic data present in this study, strain P-1km-3should be assigned to a new genus, Marinicanda gen nov., within the family Hyphomonadaceae, as type strain (=KACC16526T=CGMCC1.11031T) of a novel specie, namely Mariniciauda pacifica, sp. nov..