Plastorhodobacter daqingensis gen. nov., sp. nov.: a non-phototrophic bacterium isolated from Daqing Oilfield.

Two aerobic Gram staining negative, non-motile, and rod-shaped strains, DQW12E81-30(T) and DQW12E6-37-1, were isolated from an oil production mixture from Daqing Oilfield, northeastern China. Phylogenetic analysis based on the nearly complete 16S rRNA gene sequences revealed that strains DQW12E81-30(T) and DQW12E6-37-1 were members of family Rhodobacteraceae, which showed 95.6-95.9 % of 16S rRNA gene sequence similarities with Pararhodobacter aggregans DSM 18938(T), Rhodobacter veldkampii CGMCC 1.5006(T), and Roseinatronobacter thiooxidans DSM 13087(T), and lower similarities (<95.1 %) with all the left type species. Growth of strains DQW12E81-30(T) and DQW12E6-37-1 occurred at pH 7-8, 15-45 °C, and 0-4 % (w/v) of NaCl. The strains could grow both in dark and in light, but neither photosynthetic pigments nor photosynthetic reaction center gene pufM were detected in the strains. These photosynthesis-related features of the two isolates were different from those of Rhodobacter and Roseinatronobacter bacteria, but similar with those of Pararhodobacter. The genomic DNA G+C contents of strains DQW12E81-30(T) and DQW12E6-37-1 were 66.9 and 63.7 mol%, respectively. The predominant ubiquinone was Q-10 for both the strains. The major polar lipids of strain DQW12E81-30(T) were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylcholine, unidentified aminolipid, unidentified glycolipid, and unidentified phospholipid. The two strains had C18:1 ω7c, C18:0, and C18:1 ω7c 11-methyl as the major fatty acids. In addition, the strains DQW12E81-30(T) and DQW12E6-37-1 had C16:1 ω7c/C16:1 ω6c, C12:0, C14:0, C14:0 3-OH/C16:1 iso I, C10:0 3-OH, which were remarkably different from those of Pararhodobacter and Roseinatronobacter. The results of phenotypic, genotypic, and chemotaxonomic characteristics analyses indicated that strains DQW12E81-30(T) and DQW12E6-37-1 were readily different from their most phylogenetically closely related genera. Plastorhodobacter daqingensis gen. nov, sp. nov. is proposed for strains DQW12E81-30(T) and DQW12E6-37-1. The type strain is DQW12E81-30(T) (=LMG 27732(T)=CGMCC 1.12750(T)).