Molecular Basis of Nitrogen Fixation and the Ecological Success of the Marine Cyanobacterium Trichodesmium

蓝绿色细菌Trichodesum物种的生态成功表明，这种蓝藻具有独特的特征，在热带和亚热带海洋温暖、营养贫乏的水域具有生态优势。此外，这种没有异形囊的丝状蓝藻主导了在公海中发现的固定自由生活氮(N_2)的蓝藻。它也是唯一一种在光中固定分子氮，同时通过光合作用释放氧气的非杂胞蓝藻。以往对毛霉菌分子生物学的研究结果为研究其遗传、生化和生态等方面提供了坚实的基础。这个项目解决了毛霉生物学和生态学的三个重要问题。首先，不同菌落形态的毛霉种群间的遗传变异性是什么？第二，它在释放氧气的同时保持氧敏感固氮酶活性的能力涉及哪些机制？第三，毛霉菌在生态上的成功是否是因为它降低了对病毒感染的敏感性，这与毛霉菌DNA的广泛修饰有关？这些问题将从生化和分子方法入手，使用早期为毛霉种群开发的分子探针和抗血清来解决。

The ecological success of the blue-green bacterium Trichodesmium species suggests that this cyanobacterium possesses unique characteristics that confer an ecological advantage in the warm, nutrient-poor waters of tropical and subtropical oceans. Furthermore, this filamentous cyanobacterium without heterocysts dominates the free-living nitrogen (N2) fixing cyanobacterium found in the open ocean. It is also the only nonheterocystic cyanobacterium that fixes molecular nitrogen in the light, while evolving oxygen through photosynthesis. Results from previous studies on the molecular biology of Trichodesmium have provided a firm basis for studying its genetic, biochemical, and ecological aspects. This project addresses three important issues of Trichodesmium biology and ecology. First, what is the genetic variability among Trichodesmium populations with different colony morphologies? Second, what mechanisms are involved in its ability to maintain oxygen-sensitive nitrogenase activity while evolving oxygen? And third, is the ecological success of Trichodesmium due to its reduced susceptibility to virus infection that is related to extensive modification of Trichodesmium DNA? These issues will be addressed from biochemical and molecular approaches, using molecular probes and antisera developed earlier for Trichodesmium populations.//