Graduate School of Life Sciences, Tohoku University, Katahira, Aoba-ku, Sendai, Miyagi, Japan.
ISME J. 2010 Mar;4(3):315-26. doi: 10.1038/ismej.2009.119. Epub 2009 Nov 19.
The diversity of stem-associated bacteria of non-nodulated (Nod(-)), wild-type nodulated (Nod(+)) and hypernodulated (Nod(++)) soybeans were evaluated by clone library analyses of the 16S ribosomal RNA gene. Soybeans were dressed with standard nitrogen (SN) fertilization (15 kg N ha(-1)) and heavy nitrogen (HN) fertilization (615 kg N ha(-1)). The relative abundance of Alphaproteobacteria in Nod(+) soybeans (66%) was smaller than that in Nod(-) and Nod(++) soybeans (75-76%) under SN fertilization, whereas that of Gammaproteobacteria showed the opposite pattern (23% in Nod(+) and 12-16% in Nod(-) and Nod(++) soybeans). Principal coordinate analysis showed that the bacterial communities of Nod(-) and Nod(++) soybeans were more similar to each other than to that of Nod(+) soybeans under SN fertilization. HN fertilization increased the relative abundance of Gammaproteobacteria in all nodulation phenotypes (33-57%) and caused drastic shifts of the bacterial community. The clustering analyses identified a subset of operational taxonomic units (OTUs) at the species level in Alpha- and Gammaproteobacteria responding to both the nodulation phenotypes and nitrogen fertilization levels. Meanwhile, the abundance of Betaproteobacteria was relatively constant in all libraries constructed under these environmental conditions. The relative abundances of two OTUs in Alphaproteobacteria (Aurantimonas sp. and Methylobacterium sp.) were especially sensitive to nodulation phenotype and were drastically decreased under HN fertilization. These results suggested that a subpopulation of proteobacteria in soybeans is controlled in a similar manner through both the regulation systems of plant-rhizobia symbiosis and the nitrogen signaling pathway in plants.
采用克隆文库 16S rRNA 基因分析的方法，评估了非结瘤（Nod(-)）、野生型结瘤（Nod(+)）和超结瘤（Nod(++））大豆的茎相关细菌的多样性。大豆用标准氮（SN）施肥（15kgNha(-1)）和重氮（HN）施肥（615kgNha(-1)）处理。在 SN 施肥下，Nod(+)大豆中 Alphaproteobacteria 的相对丰度（66%）小于 Nod(-)和 Nod(++)大豆（75-76%），而 Gammaproteobacteria 的相对丰度则呈现相反的模式（Nod(+)中为 23%，Nod(-)和 Nod(++)中为 12-16%）。主坐标分析表明，在 SN 施肥下，Nod(-)和 Nod(++)大豆的细菌群落彼此之间更为相似，而与 Nod(+)大豆的细菌群落则不相似。HN 施肥增加了所有结瘤表型（33-57%）中 Gammaproteobacteria 的相对丰度，并导致细菌群落发生剧烈变化。聚类分析确定了在 Alphaproteobacteria 和 Gammaproteobacteria 中，在物种水平上对结瘤表型和氮施肥水平均有反应的操作分类单元（OTUs）的子集。同时，在这些环境条件下构建的所有文库中，Betaproteobacteria 的丰度相对稳定。Alphaproteobacteria 中两个 OTUs（Aurantimonas sp.和 Methylobacterium sp.）的相对丰度特别对结瘤表型敏感，在 HN 施肥下则急剧下降。这些结果表明，大豆中 Proteobacteria 的一个亚群通过植物-根瘤菌共生的调控系统和植物中的氮信号通路以相似的方式受到控制。
