SGER: Vector-Transformation System for Frankia

生物固氮是氮循环的关键环节。进行这种反应的能力仅限于极少数原核生物。其中的一个子集具有与高等植物形成共生关系的能力，以促进这一过程。根瘤菌属细菌，革兰氏阴性杆状菌，是这组生物中最突出的成员。根瘤菌结瘤和固氮的遗传和生物化学已被深入研究。这在很大程度上是因为适用于这类生物的遗传工具过多，以及它们与许多重要作物的关系。法兰克菌是共生固氮的另一种主要细菌。这些微生物是革兰氏阳性的丝状细菌，在各种木本植物和灌木上结瘤。表面上看，这两种细菌的运作方式相似。然而，在这两种制度之间已经确定了许多根本的区别。由于法兰克属植物生长非常缓慢，而且不与具有重要商业价值的植物形成共生关系，我们对它们的遗传学和生物化学知识极其贫乏。缺乏这些细菌的载体转化系统严重阻碍了了解其分子生物学的尝试。现在，Frankia启动子的可用性和电穿孔技术的发展，以及高灵敏度、荧光DNA和蛋白质探针的发展，使得对载体发育和转化中的许多单独步骤的系统分析成为可能，这些步骤需要完成，以便对这一重要的固氮细菌群体进行遗传分析。

Johnson 9724800 Biological nitrogen fixation is a key segment of the nitrogen cycle. The ability to carry out this reaction is limited to a very small number of prokaryotes. A sub-set of these have the capacity to form symbiotic relationships with higher plants to facilitate the process. Bacteria in the genus Rhizobia, gram-negative rods, are the most prominent member of this group of organisms. The genetics and biochemistry of nodulation and nitrogen fixation have been intensively investigated in Rhizobia. This is largely because of the plethora of genetic tools applicable to this group of organisms as well as their relationships with many important crop plants. Frankia are the other major bacterial contributor to symbiotic nitrogen fixation. These organisms are gram positive, filamentous bacteria that nodulate a wide variety of woody plants and shrubs. Superficially, the two types of bacteria have similar modes of operation. However, there are numerous fundamental differences which have been identified between the two systems. Because the Frankia are very slow growing and do not form symbioses with commercially important plants, our knowledge of their genetics and biochemistry is extremely meager. The lack of a vector-transformation system for these bacteria has seriously hampered attempts to understand their molecular biology. Now, the availability of Frankia promoters and the development of electroporation technology as well as highly sensitive, fluorescent DNA and protein probes makes feasible a systematic analysis of the many individual steps in both vector development and transformation that need to be done in order to allow genetic analysis of this important group of ntirogen-fixing bacteria.