Bradyrhizobium daqingense sp. nov., isolated from soybean nodules

Abstract

Thirteen slow-growing rhizobial strains isolated from root nodules of soybean (Glycine max L.) grown in Daqing city in China were classified in the genus Bradyrhizobium based on 16S rRNA gene sequence analysis. Multilocus sequence analysis of IGS, atpD, glnII and recA genes revealed that the isolates represented a novel clade in this genus. DNA-DNA relatedness lower than 42.5 % between the representative strain CCBAU 15774(T) and the type strains of the closely related species Bradyrhizobium liaoningense USDA 3622(T), Bradyrhizobium yuanmingense CCBAU 10071(T) and Bradyrhizobium betae LMG 21987(T), further confirmed that this group represented a novel species. CCBAU 15774(T) shared seven cellular fatty acids with the three above-mentioned species, but the fatty acids 15 : 0 iso and summed feature 5 (18 : 2ω6,9c and/or 18 : 0 anteiso) were unique for this strain. The respiratory quinone in CCBAU 15774(T) was ubiquinone-10 and the cellular polar lipids were phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, cardiolipin and unknown aminolipid, polar lipid and phospholipid. In addition, some phenotypic features could be used to differentiate the novel group from the related species. On basis of these results, we propose the name Bradyrhizobium daqingense sp. nov., with CCBAU 15774(T) ( = LMG 26137(T) = HAMBI 3184(T) = CGMCC 1.10947(T)) as the type strain. The DNA G+C content of the type strain is 61.2 mol% (T(m)).