Ultrastructure of the membrane systems in the unicellular cyanobacterium Synechocystis sp strain PCC 6803
Ultrastructure of the membrane systems in the unicellular cyanobacterium Synechocystis sp strain PCC 6803
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DOI：
10.1007/s00709-006-0145-7
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发表时间：
2006-05-01
期刊：
影响因子：
2.9
通讯作者：
Pakrasi, Himadri B.
中科院分区：
文献类型：
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作者：
Liberton, Michelle;Berg, R. Howard;Pakrasi, Himadri B.
在原核生物中，蓝藻是独特的具有高度分化的内部膜系统。像其他革兰氏阴性菌一样，蓝藻细菌如胞囊菌属菌株PCC 6803具有由质膜、肽聚糖层和外膜组成的细胞包膜。此外，这些生物有一个由类囊体膜组成的内部系统，光合作用和呼吸作用的电子转移反应在这里发生。关于这些生物的细胞超微结构，一个长期存在的争议是类囊体膜是否作为单独的隔室存在于细胞内。或者它们是否与质膜有物理连续性。细胞保存协议以及图像采集和操作技术的进步促进了对这一主题的新研究。我们使用了电子显微镜技术的组合，包括冷冻蚀刻和冷冻替代制剂。与计算机辅助图像处理相结合，生成聚囊藻细胞膜系统的高度详细图像。我们表明，在这种蓝藻中，类囊体膜实际上在物理上与质膜不连续。因此，胞囊菌菌株PCC 6803中的类囊体膜代表了真正的胞内细胞器，这是原核细胞中此类隔室的第一个例子。
Among prokaryotes, cyanobacteria are unique in having highly differentiated internal membrane systems. Like other Gram-negative bacteria, cyanobacteria such as Synechocystis sp. strain PCC 6803 have a cell envelope consisting of a plasma membrane, peptidoglycan layer, and outer membrane. In addition, these organisms have an internal system of thylakoid membranes where the electron transfer reactions of photosynthesis and respiration occur. A long-standing controversy concerning the cellular ultrastructures of these organisms has been whether the thylakoid membranes exist inside the cell as separate compartments. or if they have physical continuity with the plasma membrane. Advances in cellular preservation protocols as well as in image acquisition and manipulation techniques have facilitated a new examination of this topic. We have used a combination of electron microscopy techniques, including freeze-etched as well as freeze-substituted preparations. in conjunction with computer-aided image processing to generate highly detailed images of the membrane systems in Synechocystis cells. We show that the thylakoid membranes are in fact physically discontinuous from the plasma membrane in this cyanobacterium. Thylakoid membranes in Synechocystis sp. strain PCC 6803 thus represent bona fide intracellular organelles, the first example of such compartments in prokaryotic cells.