Azospirillum thermophilum sp. nov., isolated from a hot spring

Abstract

A novel Gram-staining negative, aerobic, motile by flagellum, rod-shaped bacterium, designated CFH 70021^T was isolated from a hot spring soil sample collected from Tengchong, Yunnan province, PR China. Growth of CFH 70021^T occurred at 15-50 °C (optimum 50 °C), pH 5.0-7.0 (optimum pH 7.0) and with 0-3.0 % (w/v) NaCl (optimum 0 %, w/v). The genome of CFH 70021^T consisted of four complete circular chromosomes and five plasmids, the genomic DNA G+C content was 69.3 mol%. Comparison of the 16S rRNA gene sequences indicated that CFH 70021^T represented a member of the genus <i>Azospirillum</i> and showed close relationship with the type strains of <i>Azospirillum agricola</i> CC-HIH038^T (97.8 %), <i>Azospirillum rugosum</i> IMMIB AFH-6^T (97.6 %), <i>Azospirillum doebereinerae</i> GSF71^T (97.6 %), <i>Azospirillum thiophilum</i> DSM 21654^T (97.4 %) and <i>Azospirillum picis</i> IMMIB TAR-3^T (97.2 %). The polar lipids of CFH 70021^T contained diphosphatidylglycerol, phosphatidylmehtylethanolamine, phosphatidylglycerol, phosphatidylcholine, two aminolipids and an unidentified phospholipid. The predominant cellular fatty acids (>10 %) included C_19:0cyclo ω<i>8c</i> (11.4 %), C_{16 : 0} (27.6 %) and summed feature 8 (C_18:1ω7<i>c</i>/C_18:1ω6<i>c</i>, 40.9 %). The major isoprenoid quinone was Q-10. On the basis of the low ANIb result (<78 %) and different phenotypic and chemotaxonomic characters, we conclude that strain CFH 70021^T represents a novel member of the genus <i>Azospirillum</i>, for which the name <i>Azospirillum thermophilum</i> sp. nov. is proposed. The type strain is CFH 70021^T (=KCTC 62259^T= CCTCC AB2018121^T).