Rhizobium alvei sp. nov., isolated from a freshwater river

Abstract

A bacterial strain designated TNR-22T was isolated from a freshwater river in Taiwan and characterized using a polyphasic taxonomic approach. Cells of strain TNR-22T were facultatively anaerobic, Gram-stain-negative, rod-shaped, motile by a single polar flagellum and formed cream-coloured colonies. Growth occurred at 4–45 °C (optimum, 25–30 °C), with 0–1.0 % (w/v) NaCl (optimum, 0.5 %) and at pH 7.0–8.0 (optimum, pH 7.0). Strain TNR-22T did not form nodules on Macroptilium atropurpureum. The nifH gene encoding denitrogenase reductase was not detected by PCR. The major fatty acids (>10 %) of strain TNR-22T were C18 : 1ω7c and C16 : 0. The DNA G+C content was 60.3 mol%. The polar lipid profile consisted of a mixture of phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, diphosphatidylglycerol, an uncharacterized aminoglycolipid and an uncharacterized phospholipid. Comparative analysis of 16S rRNA gene sequences showed that strain TNR-22T constituted a distinct branch within the genus Rhizobium , showing the highest level of sequence similarity with Rhizobium rosettiformans W3T (96.3 %). Phenotypic characteristics of the novel strain also differed from those of the most closely related species of the genus Rhizobium . On the basis of the genotypic, chemotaxonomic and phenotypic data, strain TNR-22T represents a novel species in the genus Rhizobium , for which the name Rhizobium alvei sp. nov. is proposed. The type strain is TNR-22T ( = BCRC 80408T = LMG 26895T = KCTC 23919T).