A novel species of endophytic actinobacterium, designated strain GBK3QG-3T, was isolated from surface-sterilized root of Kandelia candel collected from Beilun Estuary, Guangxi Zhuang Autonomous Region, PR China. Cells of strain GBK3QG-3T were Gram-stain-positive, aerobic, non-spore-forming and rod-shaped. Growth of GBK3QG-3T was observed at 10-40 °C (optimum, 30 °C), pH 5.0-9.0 (optimum, pH 7.0) and in the presence of 0-3 % (w/v) NaCl (optimum, 0 %). The G+C content of genomic DNA was determined to be 72.2 mol%. On the basis of 16S rRNA gene sequence analysis, strain GBK3QG-3T was most related to the type strain of Nocardioides agrisoli CCTCC AB 2017058T (97.7 % 16S rRNA gene sequence similarity), followed by Nocardioides ginkgobilobae SYP-A7303T (97.0 %) and Nocardioides aquiterrae GW-9T (96.9 %). Average nucleotide identity and digital DNA-DNA hybridization values between strain GBK3QG-3T and some strains of the genus Nocardioides with publicly available genomes were below 84.3 and 30.0 %, respectively. The cell-wall peptidoglycan contained ll-diaminopimelic acid. The polar lipids comprised diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, an unknown phospholipid and an unknown lipid. The major menaquinone was identified as MK-8(H4), and the major fatty acids were identified as iso-C16 : 0, iso-C17 : 0 and anteiso-C17 : 0. Based on evidence collected from the phenotypic, genotypic and phylogenetic analyses, we propose a novel species named Nocardioides mangrovi sp. nov. The type strain is GBK3QG-3T (=CGMCC 4.7708T=JCM 34553T).
Keywords: Kandelia candel; Nocardioides mangrovi; endophytic actinobacterium; strain GBK3QG-3T.