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

蓝绿色细菌Trichodesmium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的温暖，营养贫乏的水域中具有生态优势。此外，这种没有异囊的丝状蓝藻在开放海洋中发现的自由生活的氮（N2）固定蓝藻中占主导地位。它也是唯一一种在光线下固定分子氮，同时通过光合作用进化出氧气的非异囊蓝藻。以往对木霉分子生物学的研究成果为其遗传学、生物化学和生态学方面的研究提供了坚实的基础。本项目探讨了木霉菌生物学和生态学的三个重要问题。首先，不同菌落形态的菌群间的遗传变异性是什么？其次，在进化氧气的过程中，维持对氧敏感的氮酶活性的能力涉及什么机制？第三，木霉菌在生态上的成功是因为它对病毒感染的易感性降低了吗？这与木霉菌DNA的广泛修饰有关？这些问题将从生化和分子的角度来解决，使用分子探针和早期开发的针对木霉种群的抗血清

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.//