西北半干旱地区黄芪根瘤菌DNA同源性及16S rDNA全序列分析

 数值分类表明 ,分离自西北半干旱地区的 9株黄芪根瘤菌构成一个独立的表观群。在此基础上 ,进行了DNA同源性及 16 S r DNA全序列分析。 9株菌的 G +C mol%在 5 9.1～ 6 0 .3之间 ;群内 DNA同源性为 81.5 %～91.0 % ,大于 70 % ;中心菌株 SH2 90 B与各已知种模式菌株 DNA同源性在 10 .5 %～ 6 3.0 % ,小于 70 %。 SH2 90 B的16 S r DNA全序列与参比菌株的序列进行比较 ,得到系统发育树状图。其处在土壤杆菌 -山羊豆根瘤菌构成的分支中 ,与 R.galegae和 R.huatlense的 16 S r DNA全序列相似性分别为 96 .8%和 97.5 % ,大于 95 %以上 ,它们应归属于同一个属。因此 ,菌株 SH2 90 B代表一个新的根瘤菌种

Study on DNA-DNA Hybridization and 16S rDNA Sequence of Rhizobia Isolated from Astragalus sp. in Semi-arid Area of Northwest of China

Based on the previous studies on numerical taxonomy ,the 9 rhizobial strains isolated from Astragulus sp.in semi arid area of North west China constituted a new phenotypic subgroup, and DNA homology and 16S rDNA sequence of representative strain were tested. The DNA G C mol% content of 9 rhizobial strains ranged from 59 1 to 60 3. The levels of DNA homology with this group ranged from 81 5% to 91 0%,and the relations between representative strain and known rhizobial species were below 63%. The full length 16S rDNA sequence of SH290B was compared with the type stains of all known species and related bacteria by PHYLIP composed a phylogenetic tree, the strain SH290B was belong to Agrobacterium R.galegae phylogenetic branch. The similarity values of 16S rDNA sequence between strain SH290 B and R.galegae, R.huatlense were 96.8% and 97.5% respectively,the values were more than 95%,this indicated that these species should belong to the same genus. Thus, the strain SH290B represented a new rhizobial species.