陈文峰的博客分享 http://blog.sciencenet.cn/u/陈文峰 专注于根瘤菌的研究

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豆科植物根瘤内发现能固氮的放线菌

已有 4405 次阅读 2010-6-28 12:12 |个人分类:结瘤豆科植物|系统分类:科研笔记|关键词:豆科植物,根瘤,放线菌,小单胞菌属| 放线菌, 豆科植物, 根瘤, 小单胞菌属

放线菌中的Frankia通常与桤木形成共生固氮的根瘤,不能与豆科植物形成根瘤。Trujillo等人的新近研究表明,放线菌中的另外一类菌——小单胞菌属的细菌却能与豆科植物(如狭叶羽扇豆)形成根瘤,并且根瘤有固氮活性,扩增到的nifH基因与Frankia的相似性高达99%。原位杂交也表明,这些小单胞菌属的放线菌确实存在于根瘤内。其形成根瘤的机制还不清楚。另外由于Frankia没有根瘤菌所拥有的结瘤基因(nod),小单胞菌属是否拥有结瘤基因,也还未知。

相关论文如下:

ISME J. 2010 May 6. [Epub ahead of print]

The genus Micromonospora is widespread in legume root nodules: the example of Lupinus angustifolius.

Trujillo ME, Alonso-Vega P, Rodríguez R, Carro L, Cerda E, Alonso P, Martínez-Molina E.

Departamento de Microbiología y Genética, Edificio Departamental Lab. 205, Campus Miguel de Unamuno, Universidad de Salamanca, Salamanca, Spain.

Abstract

Our current knowledge of plant-microbe interactions indicate that populations inhabiting a host plant are not restricted to a single microbial species but comprise several genera and species. No one knows if communities inside plants interact, and it has been speculated that beneficial effects are the result of their combined activities. During an ecological study of nitrogen-fixing bacterial communities from Lupinus angustifolius collected in Spain, significant numbers of orange-pigmented actinomycete colonies were isolated from surface-sterilized root nodules. The isolates were analysed by BOX-PCR fingerprinting revealing an unexpectedly high genetic variation. Selected strains were chosen for 16S rRNA gene sequencing and phylogenetic analyses confirmed that all strains isolated belonged to the genus Micromonospora and that some of them may represent new species. To determine the possibility that the isolates fixed atmospheric nitrogen, chosen strains were grown in nitrogen-free media, obtaining in some cases, significant growth when compared with the controls. These strains were further screened for the presence of the nifH gene encoding dinitrogenase reductase, a key enzyme in nitrogen fixation. The partial nifH-like gene sequences obtained showed a 99% similarity with the sequence of the nifH gene from Frankia alni ACN14a, an actinobacterium that induces nodulation and fixes nitrogen in symbiosis with Alnus. In addition, in situ hybridization was performed to determine if these microorganisms inhabit the inside of the nodules. This study strongly suggests that Micromonospora populations are natural inhabitants of nitrogen-fixing root nodules.The ISME Journal advance online publication, 6 May 2010; doi:10.1038/ismej.2010.55.

PMID: 20445637 [PubMed - as supplied by publisher]



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