Wei Gehong, Chen Weimin, Young J Peter W, Bontemps Cyril
College of Life Sciences, Shaanxi Key Laboratory of Molecular Biology for Agriculture, Northwest A & F University, Yangling Shaanxi 712100, China.
Syst Appl Microbiol. 2009 Feb;32(1):8-16. doi: 10.1016/j.syapm.2008.11.003. Epub 2008 Dec 10.
We isolated 33 nodule bacteria from the legume Alhagi sparsifolia growing in the desert of northwest China. They fell into three groups by restriction analysis of their rrs (small subunit ribosomal RNA) genes, and these, together with dnaK and dnaJ genes, were sequenced from representative isolates to assess their taxonomic position by phylogenetic analysis. The bacteria in each group belonged to different lineages that might represent three different new Mesorhizobium species, two of which form a novel clade very distinct from other species in the genus. Most A. sparsifolia symbionts harboured closely related nodA and nodC genes forming new lineages. The presence of these closely related symbiosis genes in various genomic backgrounds and the incongruence observed between the different gene phylogenies indicate a history of horizontal gene transfer of symbiosis genes between the A. sparsifolia symbionts.
我们从生长在中国西北沙漠地区的豆科植物骆驼刺中分离出33株根瘤菌。通过对其rrs（小亚基核糖体RNA）基因进行限制性分析，这些根瘤菌被分为三组，并从代表性菌株中对rrs、dnaK和dnaJ基因进行测序，通过系统发育分析来评估它们的分类地位。每组中的细菌属于不同的谱系，可能代表三个不同的新中慢生根瘤菌物种，其中两个形成了一个与该属其他物种截然不同的新分支。大多数骆驼刺共生菌含有密切相关的nodA和nodC基因，形成了新的谱系。这些密切相关的共生基因存在于各种基因组背景中，并且在不同基因系统发育之间观察到不一致，这表明骆驼刺共生菌之间存在共生基因水平转移的历史。
