Nocardioides endophyticus sp. nov. and Nocardioides conyzicola sp. nov., isolated from herbaceous plant roots

Abstract

Two Gram-stain-positive, non-motile, non-spore-forming, rod-shaped actinobacterial strains were isolated from the surface-sterilized roots of mugwort (Artemisia princeps) and horse-weed (Conyza canadensis), and subjected to taxonomic characterization. 16S rRNA gene sequence analysis indicated that the isolates, designated MWE 3-5(T) and HWE 2-02(T), should be placed in the genus Nocardioides of the family Nocardioidaceae. The strains were closely related to Nocardioides hankookensis DS-30(T), which exhibited 16S rRNA gene sequence similarity values of 97.99 and 99.09 % with strains MWE 3-5(T) and HWE 2-02(T), respectively. The genome relatedness of N. hankookensis DS-30(T) with strain MWE 3-5(T) was 35.8 %, and that with strain HWE 2-02(T) was 36.4 %, whereas that between the two isolates was 43.2 %. Strains MWE 3-5(T) and HWE 2-02(T) possessed MK-8(H4) as the major isoprenoid quinone, and ll-diaminopimelic acid in the cell-wall peptidoglycan. The main fatty acids were iso-C16 : 0, iso-C17 : 0 and C18 : 1ω9c for strain MWE 3-5(T) and iso-C16 : 0, 10-methyl C18 : 0 and C18 : 1ω9c for strain HWE 2-02(T). Based on phenotypic, genotypic and phylogenetic studies, the following two novel species are proposed: Nocardioides endophyticus sp. nov. (type strain, MWE 3-5(T) = KCTC 29122(T) = JCM 18532(T)) and Nocardioides conyzicola sp. nov. (type strain, HWE 2-02(T) = KCTC 29121(T) = JCM 18531(T)).