Grönemeyer Jann Lasse, Bünger Wiebke, Reinhold-Hurek Barbara
Department of Microbe-Plant Interactions, Center of Molecular Interactions Bremen (CBIB), Faculty of Biology and Chemistry, University of Bremen, Postfach 33 04 40, D-28334 Bremen, Germany.
Int J Syst Evol Microbiol. 2017 Dec;67(12):4884-4891. doi: 10.1099/ijsem.0.002039. Epub 2017 Oct 16.
Four strains of symbiotic bacteria from root nodules of hyacinth bean (Lablab purpureus (L.) Sweet) from Namibia were previously identified as a novel group within the genus Bradyrhizobium. To confirm their taxonomic status, these strains were further characterized by taking a polyphasic approach. The type strain possessed 16S rRNA gene sequences identical to Bradyrhizobium paxllaeri LMTR 21 and Bradyrhizobiumicense LMTR 13, the full-length sequences were identical to those retrieved from SAMN05230119 and SAMN05230120, respectively. However, the intergenic spacer sequences of the novel group showed identities of less than 93.1 % to described Bradyrhizobium species and were placed in a well-supported separate lineage in the phylogenetic tree. Phylogenetic analyses of six concatenated housekeeping genes, recA, glnII, gyrB, dnaK, atpD and rpoB, corroborated that the novel strains belonged to a lineage distinct from named species of the genus Bradyrhizobium, with highest sequence identities to Bradyrhizobiumjicamae and B. paxllaeri (below 93 %). The species status was validated by results of DNA-DNA hybridization and average nucleotide identity values of genome sequences. 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. Phylogenetic analysis of nodC and nifH genes placed the novel strains in a group with B. paxllaeri and B.lablabi. Novel strain 5-10 induces effective nodules on Lablab purpureus, Vigna subterranea, Vigna unguiculata and Arachis hypogaea. Based on our results, we conclude that our strains represent a novel species for which the name Bradyrhizobium namibiense sp. nov. is proposed, with type strain 5-10[LMG 28789, DSM 100300, NTCCM0017 (Windhoek)].
先前从纳米比亚的扁豆（Lablab purpureus (L.) Sweet）根瘤中鉴定出的四株共生细菌被确定为慢生根瘤菌属内的一个新类群。为了确认它们的分类地位，采用多相分类法对这些菌株进行了进一步表征。模式菌株的16S rRNA基因序列与帕氏慢生根瘤菌LMTR 21和因卡慢生根瘤菌LMTR 13相同，全长序列分别与从SAMN05230119和SAMN05230120中检索到的序列相同。然而，该新类群的基因间隔序列与已描述的慢生根瘤菌物种的序列相似性低于93.1%，并在系统发育树中位于一个得到充分支持的独立分支中。对recA、glnII、gyrB、dnaK、atpD和rpoB这六个串联持家基因的系统发育分析证实，这些新菌株属于一个与慢生根瘤菌属已命名物种不同的分支，与菜豆慢生根瘤菌和帕氏慢生根瘤菌的序列相似性最高（低于93%）。通过DNA-DNA杂交结果和基因组序列的平均核苷酸同一性值验证了该物种的地位。包括碳源利用和抗生素抗性在内的多项测试的表型特征组合可用于区分慢生根瘤菌属已确认物种的代表性菌株。对nodC和nifH基因的系统发育分析将新菌株与帕氏慢生根瘤菌和扁豆慢生根瘤菌归为一组。新菌株5-10能在扁豆、非洲豇豆、豇豆和花生上诱导形成有效根瘤。基于我们的结果，我们得出结论，我们的菌株代表一个新物种，为此提出了纳米比亚慢生根瘤菌（Bradyrhizobium namibiense sp. nov.）这一名称，模式菌株为5-10[LMG 28789, DSM 100300, NTCCM0017（温得和克）]。
