College of Life Sciences, Shaanxi Key Laboratory of Molecular Biology for Agriculture, Northwest A & F University, Yangling, Shaanxi, 712100, China.
Syst Appl Microbiol. 2010 Dec;33(8):468-77. doi: 10.1016/j.syapm.2010.08.004. Epub 2010 Oct 20.
A total of seventy-five symbiotic bacterial strains isolated from root nodules of wild Sophora alopecuroides grown in different regions of China's Loess Plateau were characterized. Based on the combined RFLP patterns, thirty-five genotypes were defined among the rhizobia and they were classified into nine genomic species, including Mesorhizobium alhagi and M. gobiense as the main groups, as well as Agrobacterium tumefaciens, M. amorphae, Phyllobacterium trifolii, Rhizobium giardinii, R. indigoferae, Sinorhizobium fredii and S. meliloti as the minor groups according to the 16S rRNA and recA gene analyses. Five and three lineages of nodA and nifH were found, respectively, in these strains, implying that the symbiotic genes of the S. alopecuroides rhizobia had different origins or had divergently evolved. Results of correspondence analysis showed that there was a correlation between rhizobial genotypes and the geographic origins. Possible lateral transfer of the recA and 16S rRNA genes between the P. trifolii and A. tumefaciens strains, and that of symbiotic genes (nodA, nifH) between different genera, was shown by discrepancies of the phylogenetic relationships of the four gene loci. These results revealed diverse rhizobia associated with wild S. alopecuroides grown in different regions of China's Loess Plateau, and demonstrated for the first time the existence of symbiotic A. tumefaciens strains in root nodules of S. alopecuroides.
从中国黄土高原不同地区生长的野生苦参根瘤中分离出的 75 株共生细菌菌株进行了特征描述。基于组合 RFLP 图谱，在根瘤菌中定义了 35 种基因型，它们被分为 9 个基因组种，包括苜蓿中华根瘤菌和 M. gobiense 为主要群，以及根癌农杆菌、M. amorphae、三叶草根瘤菌、R. giardinii、R. indigoferae、中华根瘤菌和 S. meliloti 为次要群。根据 16S rRNA 和 recA 基因分析，在这些菌株中发现了 5 个和 3 个 nodA 和 nifH 谱系，这表明苦参根瘤菌的共生基因具有不同的起源或已经发生了分歧进化。对应分析的结果表明，根瘤菌基因型与地理起源之间存在相关性。P. trifolii 和根癌农杆菌菌株之间 recA 和 16S rRNA 基因的可能横向转移，以及不同属之间共生基因（nodA、nifH）的可能横向转移，是由四个基因座的系统发育关系差异所表明的。这些结果揭示了与中国黄土高原不同地区生长的野生苦参相关的多样化根瘤菌，并首次证明了共生根癌农杆菌菌株存在于苦参根瘤中。
