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

A novel endophytic bacterium, designated strain HZ10, 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 HZ10 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 C16 : 0, summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) and summed feature 3 (C16 : 1ω7c and/or C16 : 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 HZ10 is Herbaspirillum chlorophenolicum CPW301 (98.72 % sequence identity). Genome relatedness of the type strains H. chlorophenolicum CPW301, Herbaspirillum seropedicae Z67 and Herbaspirillum aquaticum IEH 4430, 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 HZ10 belongs to the genus Herbaspirillum as a novel species. Based on the results from phylogenetic, chemotaxonomic and physiological analyses, strain HZ10 represents a novel Herbaspirillum species, for which the name Herbaspirillum robiniae sp. nov. is proposed. The type strain is HZ10 (=JCM 31754=CCTCC AB 2014352).