Azospirillum tabaci sp. nov., a bacterium isolated from rhizosphere soil of Nicotiana tabacum L.

Strain W712T was isolated from rhizosphere soil of Nicotiana tabacum L. collected from Kunming, south-west China. Cells were Gram-staining negative, aerobic, motile and rod shaped. The isolate grew at 20-45 °C (optimum 30 °C), pH 6.0-8.0 (optimum pH 7.0) and in the presence of up to 3.0% (w/v) NaCl (optimum 1%, w/v). Ubiquinone-10 was the only respiratory quinone type. Polar lipids contained diphosphatidylglycerol, phosphatidylmehtylethanolamine, phosphatidylglycerol, phosphatidylcholine and an unidentified aminolipid. The major fatty acids were detected as summed feature 8 (C18:1 ω7c or C18:1 ω6c), summed feature 3 (C16:1 ω7c or C16:1 ω6c) and C18:1 2OH. The genomic DNA G + C content was 68.7%. The ANI values were 94.3%, 93.3% and 93.6% between Azospirillum baldaniorum Sp245T, Azospirillum brasilense ATCC 49958T, Azospirillum formosense CC-Nfb-7T and strain W712T, respectively, which were lower than the prokaryotic species delineation threshold of 95.0-96.0%. The digital DNA-DNA hybridization values between A. baldaniorum Sp245T, A. brasilense ATCC 49958T, A. formosense CC-Nfb-7T and strain W712T indicated that the candidate represents a novel genomic species. According to the phenotypic and genotypic characteristics, we propose that strain W712T warrants the assignment to a novel species, for which the name Azospirillum tabaci sp. nov. (type strain W712T = CGMCC 1.18567T = KCTC 82186T) is proposed.