Molecular biological analysis of the nitrogen-fixation ability of Sphingomonas paucimobilis

现代农业依赖于大量的化学氮肥。这种依赖导致了环境的自营养化和大量化石燃料的消耗，造成了诸如促进全球变暖等环境影响。为了改善现代农业的这一趋势，我们正在计划利用生物固氮在田间持续供应氮源。从水稻根际分离到重氮滋养菌鞘单胞菌（Sphingomonas paucimobilis Y39）。后来，人们发现许多鞘氨单胞菌存在于水稻叶片表面或水稻植株中。我认为s.p haucimobilis Y39可以作为水稻内生菌，通过生物固氮的方式从水稻根际两侧和植株内为水稻提供高效的氮素。目前，少动鞘单胞菌Y39更名为偶氮鞘单胞菌Y39。一开始，我将GFP基因导入s.a otifigens Y39的目的是为了证明其在水稻植物中的存在，即证明s.a otifigens Y39的内生能力。然而，这种细菌的转化是困难的，我还没有获得表达gfp的转化。于是，我开始从水稻旗叶中分离出其他重氮营养型内生鞘氨单胞菌，希望获得的鞘氨单胞菌能够容易导入GEP基因。然而，我还没有分离重氮养鞘单胞菌。

Modern agriculture relies on large amount of chemical nitrogen fertilizer. This dependence has led to environmental eutorophicaton and consumption of much fossil fuel which causes environmental impact such as the promotion of global warming. To improve this tendency of modern agriculture, we are planning the continuous supply of nitrogen source in the field by taking advantage of biological nitrogen fixation. A diazotroph in genus Sphingomonas (Sphingomonas paucimobilis Y39) was isolated form rice rhizosphere. Afterward, it was discovered that may Sphingomonas bacteria are present on the surface of rice leaves or in rice plants. I expected that S.paucimobilis Y39 could be an endophyte of rice and provide efficient nitrogen to rice from both sides of the rice rhizosphexe and in plant by biological nitrogen fixation.At present, Sphingomonas paucimobilis Y39 was renamed Sphinomonas azotifigens Y39. At the beginning, I aimed to introduce the GFP gene into S.azotifigens Y39 for the purpose of demonstration of its presence in rice plants, i.e. demonstration of endophytic ability of S.azotifigens Y39. However, transformation of this bacterium was difficult and I have not obtained a GFP-expressing transformant. Thus, I started to isolate other endophytic Sphingomonas diazotrophs from flag leaves of rice, expecting that the obtained Sphingomonas bacteria will be easy to introduce the GEP gene. However, I have not yet isolated Sphingomonas diazotrophs.