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

Abstract

A novel actinobacterium, strain HUAS 3T, was isolated from the rhizosphere soil of Cathaya argyrophylla collected in Hunan Province, PR China. Strain HUAS 3T 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 C17 : 1 ω8c, iso-C16 : 0, C18 : 1 ω9c, iso-C15 : 0, C16 : 0 and summed feature 3 (C16 : 1 ω6c and/or C16 : 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 3T belonged to the genus Micromonospora and showed highest similarities to Micromonospora fluminis A38T (99.44 %), Micromonospora echinospora DSM 43816T (99.23 %), Micromonospora tulbaghiae DSM 45142T (99.23 %), Micromonospora solifontis PPF5-17T (99.16 %) and Micromonospora endolithica DSM 44398T (98.96 %). Phylogenetic trees based on 16S rRNA gene sequences showed that strain HUAS 3T was closely related to M. fluminis A38T, M. tulbaghiae DSM 45142T and M. solifontis PPF5-17T. The phylogenomic tree revealed that strain HUAS 3T was closely related to Micromonospora pallida DSM 43817T. 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 3T was distinct from the type strain of M. pallida in terms of phenotypic and chemotaxonomic characteristics. In summary, strain HUAS 3T represents a novel Micromonospora species, for which the name Micromonospora cathayae sp. nov. is proposed. The type strain is HUAS 3T (=MCCC 1K08599T=JCM 36275T).