| Abstract |
Gram-stain-negative, aerobic, rod-shaped bacterial strains, designated HL-TH1T and HL-TH5, were isolated from deep seawater (1127 m depth) of the Amundsen Sea, Antarctica. Phylogenetic analyses based on the 16S rRNA gene sequence revealed that strains HL-TH1T and HL-TH5 were members of the genus Qipengyuania with close relatives Qipengyuania aerophila GH25T (99.3%), Qipengyuania pacifica NZ-96T (99.3%), Qipengyuania profundimaris G39T (99.1%) and Qipengyuania citrea RE35F/1T (98.8%). The complete genome sequences of strains HL-TH1T and HL-TH5 comprised a chromosome of 3.2 Mbp and a plasmid of 0.1 Mbp, with DNA G+C content of 64.1%. The whole genome-based comparisons using the average nt identity and digital DNA-DNA hybridization values revealed that both strains belonged to the same genomic species but were clearly discriminated (79.4-85.8% and 21.9-29.3%, respectively) from their close relatives in the genus Qipengyuania. Both strains showed optimal growth at 30 °C, pH 6.5-7.0 and 1.5-2.5% sea salts. The major fatty acids of both strains were C18:1 ω6c and/or C18:1 ω7c (37.8-38.4%), C17:1 ω6c (18.1-19.7%) and C16:1 ω6c and/or C16:1 ω7c (12.3-16.7%). The major isoprenoid quinone was ubiquinone-10. The polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and two unidentified lipids. Hence, we propose that strains HL-TH1T and HL-TH5 are assigned to a novel species belonging to the genus Qipengyuania, for which the name Qipengyuania profunda sp. nov. is proposed. The type strain is HL-TH1T (=KCCM 90517T=JCM 36585T). In addition, Q. aerophila GH25T and Q. pacifica NZ-96T were found to be the same species based on a polyphasic approach. Therefore, we propose the reclassification of Q. aerophila as a later heterotypic synonym of Q. pacifica.
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