木蓝根瘤菌的16S rDNA全序列分析及DNA-DNA杂交

通过数值分类、ＳＤＳ－全细胞蛋白电泳分析，对分离自西北黄土高原地区的木蓝根瘤菌进行了研究，获得了１个新类群。在此基础上，进行了中心菌株ＳＨＬ０４２的１６Ｓ ｒＤＮＡ全序列分析，得到系统发育树状图。 ＳＨＬ０４２与 Ｒ.ｔｒｏｐｉｃｉ Ａ、 Ｒ.ｔｒｏｐｉｃｉ Ｂ、 Ｒ.ｌｅｇｕｍｉｎｏｓａｒｕｍ、 Ｒ ｅｔｌｉ、 Ｒｈａｎａｎｅｓｉｓ、Ｒ. ｍｏｎｇｏｌｅｎｓｅ和Ｒ.ｇａｌｌｉｃｕｍ构成一个发育分支，其与这些种模式菌株 １６Ｓ　ｒＤＮＡ全序列的相似性分别为９５．４％、９５．５％、９６．３％、９５．８％、９６．３％、９７．９％和９７．７％，均大于９５％，应属于同一个属。新类群群内ＤＮＡ同源性大于８０％，而中心菌株ＳＨＬ０４２与分支内各已知种的ＤＮＡ同源性小于５０％，表明ＳＨＬ０４２代表１个新的根瘤菌菌种。

Analysis of 165 rDNA Sequence and DNA-DNA Hybridization of Rhizobia Isolated from Indigofera sp.

Based on the previous studies on numerical taxonomy and SDS-PAGE of whole-cell protein, the rhizobia strains isolated from Indigofera sp. in loess plateau area of North-west China constituted a new cluster, the 16S rDNA sequence of representative strain SHL042 was tested, and the phylogenetic tree was produced. In this tree, the strain SHL042, R tropici A, R tropici B, R leguminosarum, R etli, R hananesis, R mongolense and R gallicum constituted a branch of phylogenetic. Within this branch, the similarity values of 16S rDNA sequence were 95.4%, 95.5%, 96.3%,95.8%,96.3%,97.9% and 97.7% respectively. The values were more than 95%. This indicated that these species should belong to the same genus. The values of DNA homology in the new cluster were all more than 80%, but the values between SHL042 and the strains of these species were less than 50%. Thus, the strain SH714 represented a new rhizobia species.