An actinobacterial strain, designated R-N-C8T, was isolated from the rhizosphere soil of Arabidopsis thaliana collected in Yunnan Province, south-west China. Based on the results of 16S rRNA gene sequence analysis, strain R-N-C8T had highest similarity to Nocardioides terrae CGMCC 1.7056T (96.5%), Nocardioides opuntiae KCTC 19804T (96.3%) and Nocardioides currus IB-3T (96.1%), and lower than 96.0 % similarity to other members of the genus Nocardioides. Phylogenetic trees based on 16S rRNA gene sequences indicated that strain R-N-C8T formed an isolated branch with N. terrae CGMCC 1.7056T and N. opuntiae KCTC 19804T. The polar lipids contained phosphatidylglycerol, diphosphatidylglycerol, one unidentified phosphoglycolipid and four unidentified phospholipids in the cellular membrane. The major fatty acids were identified as iso-C16 : 0, anteiso-C17 : 0, iso-C17 : 0, summed feature 9 (iso-C17 : 1 ω9c and/or C16 : 0 10-methyl) and iso-C15 : 0. The predominant respiratory quinone was MK-8(H4) and ll-diaminopimelic acid was the diagnostic diamino acid in the cell-wall peptidoglycan. The genomic DNA G+C content was 70.9 mol%. The orthologous average nucleotide identiy values between N. terrae CGMCC 1.7056T, N. currus IB-3T and strain R-N-C8T were 77.1 and 75.1 %, respectively. DNA-DNA hybridization values between N. terrae CGMCC 1.7056T, N. currus IB-3T and strain R-N-C8T were 20.7 and 19.9 % respectively. Data from phenotypic and genotypic analyses supported that strain R-N-C8T represents a new species of Nocardioides, for which the name Nocardioides nematodiphilus sp. nov. is proposed. The type strain is R-N-C8T (=CGMCC 1.18723T= KCTC 49528T).
Keywords: Arabidopsis thaliana; Nocardioides nematodiphilus sp. nov.; polyphasic taxonomy; rhizosphere.