Herbaspirillum robiniae sp. nov., isolated from root nodules of Robinia pseudoacacia in a lead–zinc mine

A novel endophytic bacterium, designated strain HZ10T, was isolated from root nodules of Robinia pseudoacacia growing in a lead–zinc mine in Mianxian County, Shaanxi Province, China. The bacterium was Gram-stain-negative, aerobic, motile, slightly curved- and rod-shaped, methyl red-negative, catalase-positive, and did not produce H₂S. Strain HZ10T grew at 4–45 °C (optimum, 25–30 °C), pH 5–9 (optimum, pH 7–8) and 0–1 % (w/v) NaCl. The major fatty acids were identified as C_16 : 0, summed feature 8 (C_18 : 1ω7c and/or C_18 : 1ω6c) and summed feature 3 (C_16 : 1ω7c and/or C_16 : 1ω6c), and the quinone type was Q-8. The major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol. The DNA G+C content of the genomic DNA was 64.9 mol% based on the whole genome sequence. According to the 16S rRNA gene sequence analysis, the closest phylogenetic relative to strain HZ10T is Herbaspirillum chlorophenolicum CPW301T (98.72 % sequence identity). Genome relatedness of the type strains H. chlorophenolicum CPW301T, Herbaspirillum seropedicae Z67T and Herbaspirillum aquaticum IEH 4430T, was quantified by using the average nucleotide identity (86.9–88.0 %) and a genome-to-genome distance analysis (26.6 %–29.3 %), with both strongly supporting the notion that strain HZ10T belongs to the genus Herbaspirillum as a novel species. Based on the results from phylogenetic, chemotaxonomic and physiological analyses, strain HZ10T represents a novel Herbaspirillum species, for which the name Herbaspirillum robiniae sp. nov. is proposed. The type strain is HZ10T (=JCM 31754T=CCTCC AB 2014352T).