Description of a novel Bradyrhizobium species, B. xenonodulans. B. xenonodulans description

We used a genealogical concordance approach to characterize strains isolated from Acacia dealbata and Acacia mearnsii. The isolates were identified as Bradyrhizobium based on the analysis of the 16S rRNA sequences. Phylogenetic analysis of six housekeeping genes, atpD, dnaK, glnII, gyrB, recA and rpoB confirmed that these isolates represent a novel species, while pairwise average nucleotide identity (ANIb) calculations with the closest type strains resulted in values well below 95-96%. We further performed analysis of the nodA and nifD symbiotic loci, as well as phenotypic tests which revealed that there are high levels of intraspecies variation.

本研究采用谱系一致性分析法，对分离自银叶金合欢（Acacia dealbata）与黑荆树（Acacia mearnsii）的菌株进行了特征分析。通过16S rRNA基因序列分析，将上述分离菌株鉴定为慢生根瘤菌属（Bradyrhizobium）。针对atpD、dnaK、glnII、gyrB、recA及rpoB这6个持家基因开展系统发育分析后证实，这些分离菌株隶属于一个新的物种；且其与近缘模式菌株的两两平均核苷酸同源性（ANIb）计算值远低于95%-96%的物种界定阈值。本研究进一步对nodA与nifD共生基因座进行了分析，并开展表型试验，结果显示该类菌株存在较高水平的种内变异。