2007 年 21 巻 1 号 p. 22-26
A short coccoid- or rod-shaped, non-motile actinomycete strain RC825T 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 RC825T 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 RC825T is distinct from its closest phylogenetic neighbors, N. oleivorans and N. ganghwensis, with 44 and 39% relatedness, respectively. The cell-wall peptidoglycan of strain RC825T contained LL-diaminopimelic acid, indicating wall chemotype I. The predominant menaquinone was MK-8(H4). Strain RC825T had a cellular fatty acid profile containing straight-chain, branched, unsaturated and 10-methyl fatty acids, and the major fatty acid was iso-C16:0. 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 RC825T (=IAM 15416T=CCTCC AA206016T).