Nocardioides exalbidus sp. nov., a novel actinomycete isolated from lichen in Izu-Oshima Island, Japan

Abstract

A short coccoid- or rod-shaped, non-motile actinomycete strain RC825^T was isolated from lichen in Izu-Oshima Island, Japan. A polyphasic study was undertaken to establish the taxonomic position of this strain. Phylogenetic analysis based on 16S rRNA gene sequence revealed that strain RC825^T forms an evolutionary lineage within the radiation of the genus Nocardioides. In particular, it forms a coherent cluster with Nocardioides oleivorans and Nocardioides ganghwensis with high sequence similarity of 98 and 97.5%, respectively. However, DNA–DNA hybridization experiment demonstrated that strain RC825^T is distinct from its closest phylogenetic neighbors, N. oleivorans and N. ganghwensis, with 44 and 39% relatedness, respectively. The cell-wall peptidoglycan of strain RC825^T contained LL-diaminopimelic acid, indicating wall chemotype I. The predominant menaquinone was MK-8(H₄). Strain RC825^T had a cellular fatty acid profile containing straight-chain, branched, unsaturated and 10-methyl fatty acids, and the major fatty acid was iso-C_16:0. The DNA G+C content of the strain was 74 mol%. On the basis of both phenotypic and phylogenetic evidence, the strain is separated from previously described Nocardioides species, and should be assigned to represent a novel species of the genus Nocardioides, for which the name Nocardioides exalbidus sp. nov. is proposed. The type strain is strain RC825^T (=IAM 15416^T=CCTCC AA206016^T).