Hydrogen production by Chlamydomonas reinhardtii:: an elaborate interplay of electron sources and sinks
Hydrogen production by Chlamydomonas reinhardtii:: an elaborate interplay of electron sources and sinks
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DOI：
10.1007/s00425-007-0626-8
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发表时间：
2008-01-01
期刊：
影响因子：
4.3
通讯作者：
Happe, Thomas
中科院分区：
文献类型：
--
作者：
Hemschemeier, Anja;Fouchard, Swanny;Happe, Thomas
单细胞绿藻衣藻具有一种[FeFe]-氢酶HydA1(EC 1.12.7.2)，该酶与光合作用电子传递链偶联。当莱茵梭菌细胞没有硫的时候，在依赖光的反应中几天会产生大量的H-2。在这些条件下，细胞从有氧光合作用生长到无氧休眠状态，极大地改变了它们的生理状态。对潜在生理过程的了解不仅对进一步深入了解光合作用的适应性具有重要意义，而且有助于优化藻类作为H-2产生菌的生物技术应用。关于C.reinhardtii产生H-2的两个最有争议的问题是关于H-2产生的电子来源和氢酶与替代电子汇的竞争。我们利用特殊的质谱仪分析了缺乏S的莱茵梭菌的H-2代谢，并研究了光系统II(PS II)或核酮糖二磷酸羧化酶/加氧酶(Rubisco)缺乏对其的影响。我们表明，产生H-2的电子既由PSII活性提供，也由依赖于先前PSII活性的非光化学质体苯二酚还原途径提供。在一个缺乏Rubisco的菌株中，它也在硫的存在下产生H-2，H-2的产生似乎是PSII活性的唯一重要的电子吸收，并至少部分地挽救了该菌株的光敏表型。后者表明，S剥夺的莱茵梭菌细胞同化途径的下调是H-2持续进化的重要先决条件之一。
The unicellular green alga Chlamydomonas reinhardtii possesses a [FeFe]-hydrogenase HydA1 (EC 1.12.7.2), which is coupled to the photosynthetic electron transport chain. Large amounts of H-2 are produced in a light-dependent reaction for several days when C. reinhardtii cells are deprived of sulfur. Under these conditions, the cells drastically change their physiology from aerobic photosynthetic growth to an anaerobic resting state. The understanding of the underlying physiological processes is not only important for getting further insights into the adaptability of photosynthesis, but will help to optimize the biotechnological application of algae as H-2 producers. Two of the still most disputed questions regarding H-2 generation by C. reinhardtii concern the electron source for H-2 evolution and the competition of the hydrogenase with alternative electron sinks. We analyzed the H-2 metabolism of S-depleted C. reinhardtii cultures utilizing a special mass spectrometer setup and investigated the influence of photosystem II (PSII)- or ribulosebisphosphate-carboxylase/oxygenase (Rubisco)-deficiency. We show that electrons for H-2-production are provided both by PSII activity and by a non-photochemical plastoquinone reduction pathway, which is dependent on previous PSII activity. In a Rubisco-deficient strain, which produces H-2 also in the presence of sulfur, H-2 generation seems to be the only significant electron sink for PSII activity and rescues this strain at least partially from a light-sensitive phenotype. The latter indicates that the down-regulation of assimilatory pathways in S-deprived C. reinhardtii cells is one of the important prerequisites for a sustained H-2 evolution.