Bradyrhizobium kavangense sp. nov., a symbiotic nitrogen-fixing bacterium from root nodules of traditional Namibian pulses

Abstract

Eight strains of symbiotic bacteria from root nodules of local races of cowpea (Vigna unguiculata) and Bambara groundnut (Vigna subterranea) grown on subsistence farmers' fields in the Kavango region, Namibia, were previously characterized and identified as a novel group within the genus Bradyrhizobium. To clarify their taxonomic status, these strains were further characterized using a polyphasic approach. In phylogenetic analysis of the 16S rRNA gene sequence the novel group was most closely related to Bradyrhizobium iriomotense EK05 T and Bradyrhizobium ingae BR 10250 T , and to 'Bradyrhizobium arachidis' CCBAU 051107 in the ITS sequence analysis. Phylogenetic analysis of concatenated glnII-recA-rpoB-dnaK sequences placed the strains in a lineage distinct from named species of the genus Bradyrhizobium. The species status was validated by results of DNA-DNA hybridization. Phylogenetic analysis of nifH and nodC genes placed the novel strains in a group with 'B. arachidis' CCBAU 051107. The combination of phenotypic characteristics from several tests including carbon source utilization and antibiotic resistance could be used to differentiate representative strains from recognized species of the genus Bradyrhizobium. Novel strain 14-3 T induces effective nodules on Vigna subterranea, Vigna unguiculata, Arachis hypogaea and Lablab purpureus. Based on the data presented, it is concluded that the strains represent a novel species of the genus Bradyrhizobium, for which the name Bradyrhizobium kavangense sp. nov. is proposed. The type strain is 14-3 T [5DSM 100299 T 5LMG 28790 T 5NTCCM 0012 T (Windhoek)]. The DNA G+C content of strain 14-3 T is 63.8 mol% (T m ).

Bradyrhizobium archetypum sp. nov., Bradyrhizobium australiense sp. nov. and Bradyrhizobium murdochi sp. nov., isolated from nodules of legumes indigenous to Western Australia

“…Nowadays, the suggested threshold for species delineation for the genus Bradyrhizobium using five concatenated genes is 97 % NI [22]. Several phylogenetic studies have suggested a minimum of four [6, 12], or even three [8] concatenated housekeeping genes in the MLSA, and a considerable number of Bradyrhizobium species have been described using four genes and an NI value of 97 % as the threshold for species delineation [2, 13, 33, 35, 36]. In our study, both sets of genes on the MLSA presented NI for the new groups compared with the most related species far below 97 %; the only exception was of group GII.III, which shared from 97 to 97.3 % NI with B.…”

Can Bradyrhizobium strains inoculation reduce water deficit effects on peanuts?

“…Comparison of the almost complete sequence (1268 nt) of the 16S rRNA gene of strain ESA 123 showed that this isolate is classified within the B. japonicum clade with the most similarity to the strain type 14-3 T B. kavangense. This species has recently been described, isolated from peanut nodules in Namibia (Grönemeyer et al 2015) and bacteria with sequences of the 16S rRNA gene related to B. kavangense were later isolated in South Africa (Jaiswal et al 2017) and in Brazil (Santos et al 2017a). Although the 16S rRNA gene sequence shows high similarity (98.97%) to B. kavangense, the ESA 123 strain may represent a new species, since the taxonomy of Bradyrhizobium is complex and cannot be elucidated only with the 16S rRNA allele (Hungria et al 2015).…”

African origin of Bradyrhizobium populations nodulating Bambara groundnut (Vigna subterranea L. Verdc) in Ghanaian and South African soils

“…Recently, Gronemeyer et al . [ 45 , 51 – 52 ] showed that Bradyrhizobium subterraneum , Bradyrhizobium kavangense and Bradyrhizobium vignae (all of African origin) are responsible for the nodulation of Bambara groundnut. However, from the phylogenetic analysis of individual and concatenated genes in this study, there were many unknown Bradyrhizobium species from Ghanaian and South African soils that nodulated Bambara groundnut, and are still waiting to be properly described.…”