Biochemical and morphological characterization of sulfur-deprived and H2-producing Chlamydomonas reinhardtii (green alga)
Biochemical and morphological characterization of sulfur-deprived and H2-producing Chlamydomonas reinhardtii (green alga)
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DOI：
10.1007/s004250100660
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发表时间：
2002-02-01
期刊：
影响因子：
4.3
通讯作者：
Melis, A
中科院分区：
文献类型：
--
作者：
Zhang, LP;Happe, T;Melis, A
缺硫对绿色藻类光合作用的影响是可逆的。在缺乏S的情况下，光合作用释放O-2的速率低于呼吸作用消耗O-2的速率。因此，密封培养的绿色莱茵衣藻在光照下变得厌氧，诱导电子传递的“Fe-氢化酶”途径，并光合产生H-2气体。在这种H-2气体产生过程中，细胞消耗大量的内部淀粉和蛋白质。这种分解代谢反应可以直接或间接地维持H-2-生产过程。选择的光合蛋白的分析表明，在核酮糖-1，5-二磷酸羧化酶加氧酶（Rubisco）的量急剧下降，作为时间的函数在S剥夺，一个更渐进的下降水平的光系统（PS）II和PSI蛋白，和PSII捕光复合物（LHC-II）的组成的变化。在硫剥夺的初始阶段（0-72 h），注意到酶Fe氢化酶的水平增加，随后在较长的硫剥夺时间（t > 72 h），该酶的水平下降。显微镜下观察表明，C.莱茵衣藻在缺硫和H-2产生过程中，椭圆形细胞（正常光合作用）在S剥夺和H-2产生的初始阶段让位于更大和球形的细胞形状，随后在更长的S剥夺和H-2产生时间后细胞质量减少。PSII的H2O氧化活性饲料进入氢化酶途径，从而有助于H-2生产过程中的莱茵衣藻。产氧光合作用，线粒体呼吸，catalysts的内源性底物，并通过氢化酶途径的电子传递之间的相互作用是必不可少的光介导的H-2生产过程。
Sulfur deprivation in green algae causes reversible inhibition of photosynthetic activity. In the absence of S, rates of photosynthetic O-2 evolution drop below those Of O-2 consumption by respiration., As a consequence, sealed cultures of the green alga Chlamydomonas reinhardtii become anaerobic in the light, induce the "Fe-hydrogenase" pathway of electron transport and photosynthetically produce H-2 gas. In the course of such H-2-gas production cells consume substantial amounts of internal starch and protein. Such catabolic reactions may sustain, directly or indirectly, the H-2-production process. Profile analysis of selected photosynthetic proteins showed a precipitous decline in the amount of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) as a function of time in S deprivation, a more gradual decline in the level Of photosystem (PS) II and PSI proteins, and a change in the composition of the PSII light-harvesting complex (LHC-II). An increase in the level of the enzyme Fehydrogenase was noted during the initial stages of S deprivation (0-72 h) followed by a decline in the level of this enzyme during longer (t > 72 h) S-deprivation times. Microscopic observations showed distinct morphological changes in, C. reinhardtii during S deprivation and H-2 production, Ellipsoid-shaped cells (normal photosynthesis) gave way to larger and spherical cell shapes in the initial stages of S deprivation and H-2 production, followed by cell- mass reductions after longer S-deprivation and H-2-production times- It is suggested that, under S-deprivation conditions, electrons derived from a residual, PSII H2O-oxidation activity feed into the hydrogenase pathway, thereby contributing to the H-2-production process in Chlamydomonas reinhardtii. Interplay between oxygenic photosynthesis, mitochondrial respiration, catabolism of endogenous substrate, and electron transport via the hydrogenase pathway is essential for this light-mediated H-2-production process.