Nocardiopsis eucommiae sp. nov., a novel endophytic actinomycete isolated from leaves of Eucommia ulmoides Oliv.

Abstract

A novel Gram-stain-positive, endophytic actinobacterium, designated strain HDS5T, was isolated from leaves of Eucommia ulmoides Oliv. collected from Changde City, Hunan Province, PR China. Strain HDS5T produced yellowish oil green substrate mycelia on Gause’s synthetic medium, which also carried yellowish oil green aerial hyphae, fragmenting into rod-shaped elements with smooth surfaces. Strain HDS5T grew at pH 5.0–11.0 (optimum, pH 7), at 20–40 °C (optimum, 28 °C) and in the presence of 0–8.0% NaCl (w/v; optimum, 0–1.0 %). Whole-cell hydrolysates contained meso-diaminopimelic acid as the diagnostic amino acid and no diagnostic sugars. The predominant fatty acids were iso-C16:0 and C18 : 1 ω9c. The menaquinones were MK-10(H2), MK-10(H4) and MK-10(H6). Strain HDS5T showed high 16S rRNA gene sequence similarity to Nocardiopsis prasina DSM 43845T (99.72 %), Nocardiopsis ganjiahuensis DSM 45031T (99.31 %), Nocardiopsis exhalans JCM 11759T (99.17 %), Nocardiopsis alba DSM 43377T (99.11 %), Nocardiopsis metallicus KBS6T (99.11 %), Nocardiopsis valliformis DSM 45023T (99.04 %), Nocardiopsis listeri NBRC 13360T (98.97 %), Nocardiopsis lucentensis DSM 44048T (98.83 %), Nocardiopsis terrae YIM 90022T (98.83 %) and <98.7 % similarities to other type strains. Phylogenetic analysis of 16S rRNA gene sequences and whole-genome sequences showed that strain HDS5T was closely related to N. prasina DSM 43845T. However, the average nucleotide identity based on blast and digital DNA–DNA hybridization values between them were determined to be 90.1 and 40.9 %, respectively, below the threshold of 95–96 and 70 % for the delineation of prokaryotic genomic species, suggesting that strain HDS5T represents a novel Nocardiopsis species. Furthermore, the morphological and physio-biochemical characteristics were sufficient to distinguish strain HDS5T from N. prasina DSM 43845T. Consequently, based on phenotypic and genotypic characteristics, strain HDS5T represents a new Nocardiopsis species, for which the name Nocardiopsis eucommiae sp. nov. is proposed. The type strain is HDS5T (=MCCC 1K06172T=JCM 34707T).