Molecular Biology of Nitrogenase Genes in Trichodesmium, A Marine Nonheterocystous Cyanobacterium

Trichodesmium是一种光合细菌， 蓝藻，在表面形成大量的浓度 开放海洋的沃茨。它有能力修复 大气氮不像大多数其他浮游植物， 取决于氮在海水中的溶解形式，例如， 硝酸盐，用于吸收到细胞中用于随后的生长。在 有时，该物种形成密集的花朵， 重要的是海洋中新生产的瞬时速率。 自从发现固氮作用与 Trichodesmium，许多研究试图描述 固氮活性和生理特性。 然而，固氮的机制仍然不是 明白固氮酶催化还原 二氮转化为铵的过程会被氧气迅速灭活。 因此，这些生活在高氧区的生物， 表层沃茨必须以某种方式保护它们的固氮酶， 光合作用产生的氧气。 泽尔博士的工作集中在两个主要问题上：1）如何 束毛藻固氮和放氧同时进行， 2)束毛藻是否有一种独特的或可替代的固氮酶 在沃茨中合成活性固氮酶的系统 缺乏微量元素如钼。工作 确定固氮酶基因的独特特征， 利用分子技术构建基因组文库 来描述基因的结构。探针和 制备抗体以研究 自然种群和文化中的基因。

Trichodesmium is a species of photosynthetic bacteria , a cyanobacterium, which forms large concentrations in the surface waters of the open ocean. It posesses the ability to fix atmospheric nitrogen unlike most of the other phytoplankton which depend upon the dissolved forms of nitrogen in seawater , eg. nitrate, for uptake into the cell for subsequent growth. At times, this species forms dense blooms which may be extremely important in transient rates of new production in the ocean. Since the discovery of nitrogen fixation in association with Trichodesmium, many studies have attempted to characterize the nitrogen fixation activity and physiology of the species. However, the mechanisms of nitrogen fixation are still not understood. The enzyme nitrogenase which catalyzes the reduction of dinitrogen to ammonium is rapidly inactivated by oxygen. Therefore these organisms which live in the high oxygen zone of the surface waters must somehow protect their nitrogenase from the oxygen that they themselves generate during photosynthesis. Dr. Zehr focuses his work on two major questions: 1) how does Trichodesmium fix nitrogen and evolve oxygen simultaneously, and 2) does Trichodesmium posess a unique or alternative nitrogenase system that allows it to synthesize active nitrogenase in waters depleted of micronutrients such as molybdenum. The work identifies unique characteristics of the nitrogenase genes in the species using molecular techniques to construct a genomic library to characterize the organization of the gene. Probes and antibodies are to be prepared to study the expression of the genes in natural populations and cultures.