Nocardioides pini sp. nov. and Nocardioides pinisoli sp. nov., two novel actinomycetes isolated from Pinus densiflora

Abstract

Two novel Gram-positive bacteria designated as strains STR2T and STR3T were isolated from the rhizosphere of a Pinus densiflora sample collected from Goyang-si, Republic of Korea. Strains STR2T and STR3T were aerobic, rod shaped, non-sporulated, catalase negative, oxidase negative and non-motile bacteria. They grew at 15–37°C (optimum, 25–30°C), at pH 6.0–11.0 (optimum, pH 7.0) and in the presence of 0–2% NaCl (optimum, 0%, w/v). The chemotaxonomic and morphological characteristics of the novel strains were consistent with those of the members of Nocardioides. The phylogenetic analysis of the 16S rRNA gene sequences revealed that STR2T was closely related to N. cavernae YIM A1136T (99.3%) and N. flavus Y4T (99.1%), and STR3T was closely related to N. exalbidus DSM 22017T (99.0%), N. baculatus G10T (98.8%) and N. hwasunensis HFW-21T (98.7%). The average nucleotide identity, average amino acid identity and digital DNA–DNA hybridization values of STR2T and STR3T with the most closely related strains that have publicly available whole genomes were 83.1–89.8%, 80.9–89.6% and 26.2–39.1%, respectively. The cell-wall peptidoglycan of strain STR2T and STR3T contained ll-diaminopimelic acid as the diagnostic amino acid. The major fatty acids in STR2T and STR3T were iso-C16:0 and C17:1 ω8c, and the predominant quinone was MK-8(H4). Their polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and other polar lipids. The draft genome sequences showed that the genomic DNA G+C content of STR2T and STR3T were both 72.2 mol%. Physiological and biochemical tests and 16S rRNA sequence analysis clearly revealed that STR2T and STR3T could represent novel Nocardioides species. Their proposed names were as follows: Nocardioides pini sp. nov. for strain STR2T (=KACC 22784T=TBRC 16336T) and Nocardioides pinisoli sp. nov. for strain STR3T (= KACC 22785T=TBRC 16337T). © 2023 The Authors.