Micromonospora cathayae sp. nov., isolated from the rhizosphere soil of Cathaya argyrophylla

Abstract

A novel actinobacterium, strain HUAS 3^T, was isolated from the rhizosphere soil of Cathaya argyrophylla collected in Hunan Province, PR China. Strain HUAS 3^T contained meso-diaminopimelic acid in the cell-wall peptidoglycan. The dominant menaquinones were MK-9(H₄), MK-9(H₆), MK-10(H₂) and MK-9(H₄). The polar lipids consisted of diphosphatidylglycerol, phospholipids, phosphatidylethanolamine, phosphatidylglycerol, phosphotidylinositol and phosphatidylinositol mannosides. The main cellular fatty acids (>5.0 %) were C_{17 : 1} ω8c, iso-C_{16 : 0}, C_{18 : 1} ω9c, iso-C_{15 : 0}, C_{16 : 0} and summed feature 3 (C_{16 : 1} ω6c and/or C_{16 : 1} ω7c). The DNA G+C content of the novel strain's genome sequence, consisting of 7 196 442 bp, was 72.8 mol%. The full-length 16S rRNA gene sequence analysis indicated that strain HUAS 3^T belonged to the genus Micromonospora and showed highest similarities to Micromonospora fluminis A38^T (99.44 %), Micromonospora echinospora DSM 43816^T (99.23 %), Micromonospora tulbaghiae DSM 45142^T (99.23 %), Micromonospora solifontis PPF5-17^T (99.16 %) and Micromonospora endolithica DSM 44398^T (98.96 %). Phylogenetic trees based on 16S rRNA gene sequences showed that strain HUAS 3^T was closely related to M. fluminis A38^T, M. tulbaghiae DSM 45142^T and M. solifontis PPF5-17^T. The phylogenomic tree revealed that strain HUAS 3^T was closely related to Micromonospora pallida DSM 43817^T. However, the average nucleotide identity (ANIb/ANIm) and the digital DNA-DNA hybridization values between them were 84.75 /88.16 and 30.80 %, respectively, far less than the 95-96 and 70 % cut-off points recommended for delineating species. Furthermore, strain HUAS 3^T was distinct from the type strain of M. pallida in terms of phenotypic and chemotaxonomic characteristics. In summary, strain HUAS 3^T represents a novel Micromonospora species, for which the name Micromonospora cathayae sp. nov. is proposed. The type strain is HUAS 3^T (=MCCC 1K08599^T=JCM 36275^T).

Keywords: Cathaya argyrophylla; Micromonospora cathayae sp. nov.; polyphasic method.