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 STR2Tand STR3Twere isolated from the rhizosphere of aPinus densiflorasample collected from Goyang-si, Republic of Korea. Strains STR2Tand STR3Twere 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 ofNocardioides. The phylogenetic analysis of the 16S rRNA gene sequences revealed that STR2Twas closely related toN. cavernaeYIM A1136T(99.3 %) andN. flavusY4T(99.1 %), and STR3Twas closely related toN. exalbidusDSM 22017T(99.0 %),N. baculatusG10T(98.8 %) andN. hwasunensisHFW-21T(98.7 %). The average nucleotide identity, average amino acid identity and digital DNA–DNA hybridization values of STR2Tand STR3Twith 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 STR2Tand STR3Tcontainedll-diaminopimelic acid as the diagnostic amino acid. The major fatty acids in STR2Tand STR3Twere iso-C16 : 0and 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 STR2Tand STR3Twere both 72.2 mol%. Physiological and biochemical tests and 16S rRNA sequence analysis clearly revealed that STR2Tand STR3Tcould represent novelNocardioidesspecies. Their proposed names were as follows:Nocardioides pinisp. nov. for strain STR2T(=KACC 22784T=TBRC 16336T) andNocardioides pinisolisp. nov. for strain STR3T(= KACC 22785T=TBRC 16337T).