合欢、金合欢和银合欢根瘤菌系统发育研究方法比较

利用位于染色体不同位点的多个基因序列进行分析是原核生物分类与系统发育研究的一个热点.本文采用atpD和glnⅡ两个持家基因的部分序列对9株分离自我国合欢、金合欢和银合欢的根瘤菌进行系统发育研究,并与以16S rDNA基因序列构建的系统发育树进行比较.结果表明三者在属水平上基本一致,CCBAU43060、CCBAU61139位于Rhizobium-Agrobacterium系统发育分支内;CCBAU51471、CCBAU35220、CCBAU51276和CCBAU61158属于Mesorhizobium,CCBAU35234、CCBAU61178和CCBAU35085位于Bradyrhizobium系统发育分支;在属内种间个别菌株(CCBAU61158、CCBAU43060、CCBAU61178)的系统发育地位存在差异,表明属内种间存在较广泛的基因交流.因此利用16S rDNA确定属水平的分类地位比较可靠,但利用系统发育的方法研究属内种间亲缘关系应采用多个功能保守的持家基因同时进行分析才能得出比较可靠的结论.

Comparison of phylogeny analysis methods for rhizobia Albizia spp., Acacia spp. and Leucaena leucocephala

Multilocus house-keeping gene sequence analysis is a hotspot of taxonomy and phylogeny of prokaryotes. In this research, we used atpD and gln II gene sequences to analyze the phylogeny of nine rhizobia strains of Albizia spp., Acacia spp. and Leucaena leucocephala and compared the results to that of 16S rDNA. The phylogenetic relationships based on the sequence analysis of these three genes were congruent at the genera level. CCBAU43060 and CCBAU 61139 were located in the branch of Rhizobium-Agrobacterium. CCBAU51471, CCBAU35220, CCBAU51276 and CCBAU61158 belonged to the genera of Mesorhizobium. CCBAU35234, CCBAU61178 and CCBAU35085 were assigned to Bradyrhizobium. Differences were found for some strains, for example CCBAU 61158, CCBAU43060, CCBAU61178, at the species level. Insertion fragment and mosaic gene were also found in some isolates. These results indicated that there was recombination between species in the same genera. It is reliable to determine the taxonomy status at genera levels based on the sequence analysis of 16S rDNA. If the relationships between strains belonging to the same genera were studied using the phylogeny methods, researches should be carded out with more than one house-keeping genes.