A Novel Mechanism of Oxygen Cycling in Trichodesmium

海洋蓝藻Trichodesmium使用一种未知的机制来保护其氮酶免受氧气的失活。在光合作用期间，一些细胞耗氧反应可能使体内氧浓度最小化。对迄今提出的机制的分析表明，在毛霉菌落中仍有一个重要的耗氧过程有待发现。正在测试的假设是，氧的光还原（梅勒反应）除去了光合作用产生的氧气的很大一部分。验证这一假设和测量其他耗氧反应需要稳定的同位素技术。两种相关的O-18技术能够确定光下的光合析氧和耗氧速率：膜入口质谱法和O-18同位素稀释技术。将要使用的方法要么是新的，要么是以前仅限于实验室的。有了现代、可靠和紧凑的质谱仪，在海上进行稳定同位素技术是可行的。固氮蓝藻Trichodesmium必须具有某种机制，使其氮酶不会因光合作用产生的氧气而失活。氧的光还原（梅勒反应）是一个可能的途径，将在他们的项目中进行研究。一种新开发的质谱仪和氧18同位素将在加勒比海的海上使用，以测试在Trichodesmium中具有普遍重要性的Mehler反应的假设。

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.