Five bacterial strains representing 45 isolates originated from root nodules of the medicinal legume Sophora flavescens were defined as two novel groups in the genus Rhizobiumbased on their phylogenetic relationships estimated from 16S rRNA genes and the housekeeping genes recA, glnII and atpD. These groups were distantly related to Rhizobium leguminosarum USDA 2370T (95.6 % similarity for group I) and Rhizobium phaseoli ATCC 14482T (93.4 % similarity for group II) in multilocus sequence analysis. In DNA–DNA hybridization experiments, the reference strains CCBAU 03386T (group I) and CCBAU 03470T (group II) showed levels of relatedness of 17.9–57.8 and 11.0–42.9 %, respectively, with the type strains of related species. Both strains CCBAU 03386T and CCBAU 03470T contained ubiquinone 10 (Q-10) as the major respiratory quinone and possessed 16 : 0, 18 : 0, 19 : 0 cyclo ω8c, summed feature 8 and summed feature 2 as major fatty acids, but did not contain 20 : 3 ω6,8,12c. Phenotypic features distinguishing both groups from all closely related species of the genus Rhizobiumwere found. Therefore, two novel species, Rhizobium sophorae sp. nov. for group I (type strain CCBAU 03386T = E5T = LMG 27901T = HAMBI 3615T) and Rhizobium sophoriradicis sp. nov. for group II (type strain CCBAU 03470T = C-5-1T = LMG 27898T = HAMBI 3510T), are proposed. Both groups were able to nodulate Phaseolus vulgaris and their hosts of origin (Sophora flavescens) effectively and their nodulation gene nodC was phylogenetically located in the symbiovar phaseoli.
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Funding
This study was supported by the:
Chinese Universities Scientific Fund
(Award 2014QT003)
National Natural Science Foundation of China
(Award 31270052)
Instituto Politecnico Nacional, Mexico
(Award 20140124 and SIP 20130828)
Northern China Standardized Plant Base Optimization and Upgrading and Series Products Comprehensive Development of Sophora flavescens
(Award 2011BA107B03)
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