Description of Qipengyuania profunda sp. nov., isolated from deep seawater of the Amundsen Sea (Antarctica), and reclassification of Qipengyuania aerophila Liu et al. 2022 as a later heterotypic synonym of Qipengyuania pacifica Tareen et al. 2022

Gram-stain-negative, aerobic, rod-shaped bacterial strains, designated HL-TH1^T 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-TH1^T and HL-TH5 were members of the genus <i>Qipengyuania</i> with close relatives <i>Qipengyuania aerophila</i> GH25^T (99.3%), <i>Qipengyuania pacifica</i> NZ-96^T (99.3%), <i>Qipengyuania profundimaris</i> G39^T (99.1%) and <i>Qipengyuania citrea</i> RE35F/1^T (98.8%). The complete genome sequences of strains HL-TH1^T 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 <i>Qipengyuania</i>. 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 C_18:1 <i> ω</i>6<i>c</i> and/or C_18:1 <i> ω</i>7<i>c</i> (37.8-38.4%), C_17:1 <i> ω</i>6<i>c</i> (18.1-19.7%) and C_16:1 <i> ω</i>6<i>c</i> and/or C_16:1 <i> ω</i>7<i>c</i> (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-TH1^T and HL-TH5 are assigned to a novel species belonging to the genus <i>Qipengyuania</i>, for which the name <i>Qipengyuania profunda</i> sp. nov. is proposed. The type strain is HL-TH1^T (=KCCM 90517^T=JCM 36585^T). In addition, <i>Q. aerophila</i> GH25^T and <i>Q. pacifica</i> NZ-96^T were found to be the same species based on a polyphasic approach. Therefore, we propose the reclassification of <i>Q. aerophila</i> as a later heterotypic synonym of <i>Q. pacifica</i>.