Physiology, Ecology and Biochemistry of Nitrogen Fixation byMarine Planktonic Microorganisms

博士。卡彭特和卡彭提议继续研究浮游微生物，特别是非异囊蓝藻毛藻中 N2 固定的生物化学、生理学和生态学。 这些研究非常重要，因为毛藻是热带和亚热带海洋浮游植物种群的重要组成部分，也是这些系统新氮的主要贡献者。 此外，Trichodesmium 的固氮酶系统在几个方面似乎与研究更充分的非异囊类似物不同。 了解Trichodesmium用于维持活性固氮的生化和分子机制具有广泛的相关性。 他们将确定调节 Trichodesmium 中 N2 固定和生长的因素（生物化学和生态），及其在海洋食物网中的重要性。 具体来说，他们将进行以下研究：1）保护固氮酶免于氧失活的机制（氧保护酶系统，如超氧化物歧化酶、摄取氢化酶等）； 2)控制固氮酶合成和活性的表观内源节律的因素，以及固氮酶合成和活性调节的因素，ATP/ADP比率)； 3) 集落内固定氮如何在固定氮和非固定细胞之间转移； 4）浮力昼夜变化的原因和意义； 5) 最近由 Trichodesmium 在近地表水中固定的氮和碳的命运。 该研究项目的独特之处在于它汇集了不同的研究人员小组，研究有关毛藻和其他公海固氮菌的生物学和生态学的广泛主题。

Drs. Carpenter and Capone propose to continue their investigations of the biochemistry, physiology and ecology of N2 fixation in planktonic microorganisms, and particularly the non-heterocystous cyanobacterium Trichodesmium. These studies are important as Trichodesmium is a substantial component of the phytoplankton populations of tropical and subtropical seas and a major contributor of new nitrogen to these systems. Furthermore, the nitrogenase enzyme system of Trichodesmium appears distinct in several respects from the more well studied non-heterocystous analogues. An understanding of the biochemical and molecular mechanisms used by Trichodesmium to maintain active nitrogen fixation would be of broad relevance. They will determine the factors (biochemical and ecological) which regulate N2 fixation and growth in Trichodesmium, as well as its importance in the marine food web. Specifically, they will pursue studies of: 1) the mechanisms for protecting nitrogenase from oxygen deactivation (oxygen protective enzyme systems such as superoxide dismutase, uptake hydrogenases etc.); 2) factors controlling the apparent endogenous rhythms of nitrogenase synthesis and activity, and of regulation of nitrogenase synthesis and activity, ATP/ADP ratios); 3) how fixed nitrogen is transferred between N2 fixing and non-fixing cells within a colony; 4) the causes and significance of diel changes in buoyancy; and 5) the fate of nitrogen and carbon recently fixed by Trichodesmium in near surface waters. This research program is unique in that it brings together a diverse group of investigators to work on a broad array of topics concerning the biology and ecology of Trichodesmium and other open ocean nitrogen fixers.