A Novel Mechanism of Oxygen Cycling in Trichodesmium

海洋蓝细菌Trichodesmium使用一种未经鉴定的 保护固氮酶不失活的机制 通过氧气。 几种细胞耗氧反应可能 最大限度地减少体内氧浓度期间， 光合作用 对迄今提出的机制的分析 表明仍有一个重要的 氧消耗过程中的Trichodesmium菌落。 的 一个正在被验证的假设是， （Mehler反应）去除了很大一部分的 光合作用释放氧气。 对这一假设的检验 以及其它耗氧反应的测量需要 稳定同位素技术 两种相关的O-18技术是 能够确定光合放氧， 光中的耗氧速率：膜入口质量 光谱法和O-18同位素稀释技术。 的方法 使用的是新的或仅限于实验室 以前 凭借现代化、可靠和紧凑的质谱仪 在海上开展稳定同位素技术是可行的。 %%% 固氮蓝藻束毛藻必须具备 一些固氮酶不 光合作用产生的氧气使其失活。 的 氧气的光还原（Mehler反应）是一种可能的方法。 这将在他们的项目中进行调查的途径。 一个新 将使用先进的质谱仪和氧18同位素 在加勒比海上测试了一个假设， 在束毛藻属中具有普遍重要性的反应。

The marine cyanobacterium Trichodesmium uses an unidentified mechanism to protect its nitrogenase enzyme from deactivation by oxygen. Several cellular oxygen consuming reactions may minimize the in vivo oxygen concentration during periods of photosynthesis. Analysis of the mechanisms proposed to date indicates that there remains to be discovered a significant oxygen consuming process in the Trichodesmium colonies. The hypothesis being tested is that the photoreduction of oxygen (Mehler reaction) removes a significant fraction of photosynthetically evolved oxygen. Tests of this hypothesis and measurement of other oxygen consuming reactions require stable isotope techniques. Two related O-18 techniques are capable of determining photosynthetic oxygen evolution and oxygen consumption rates in the light: membrane inlet mass spectrometry and O-18 isotope dilution techniques. The methods to be used are either new or have been confined to laboratories before. With modern, reliable and compact mass spectrometers it is feasible to conduct stable isotope techniques at sea. %%% The nitrogen-fixing cyanobacterium Trichodesmium must possess some mechanism whereby its nitrogenase enzyme is not deactivated by oxygen produced during photosynthesis. The photoreduction of oxygen (Mehler reaction) is a possible pathway which will be investigated in thei project. A newly developed mass spectrometer and oxygen 18 isotopes will be used at sea in the Caribbean to test the hypothesis that the Mehler reaction of general importance in Trichodesmium.