Martinez-Planells Asunción, Arellano Juan B, Borrego Carles M, López-Iglesias Carmen, Gich Frederic, Garcia-Gil Jesús
Section of Microbiology. Institute of Aquatic Ecology, University of Girona, Campus de Montilivi, E-17071, Girona, Spain,
Photosynth Res. 2002;71(1-2):83-90. doi: 10.1023/A:1014955614757.
Isolated chlorosomes of several species of filamentous anoxygenic phototrophic bacteria (FAPB) and green sulfur bacteria (GSB) were examined by atomic force microscopy (AFM) to characterize their topography and biometry. Chlorosomes of Chloroflexus aurantiacus, Chloronema sp., and Chlorobium (Chl.) tepidum exhibited a smooth surface, whereas those of Chl. phaeobacteroides and Chl. vibrioforme showed a rough one. The potential artifactual nature of the two types of surfaces, which may have arisen because of sample manipulation or AFM processing, was ruled out when AFM images and transmission electron micrographs were compared. The difference in surface texture might be associated with the specific lipid and polypeptide composition of the chlorosomal envelope. The study of three-dimensional AFM images also provides information about the size and shape of individual chlorosomes. Chlorosomal volumes ranged from ca. 35 000 nm(3) to 247 000 nm(3) for Chl. vibrioforme and Chl. phaeobacteroides, respectively. The mean height was about 25 nm for all the species studied, except Chl. vibrioforme, which showed a height of only 14 nm, suggesting that GSB have 1-2 layers of bacteriochlorophyll (BChl) rods and GFB have approximately 4. Moreover, the average number of BChl molecules per chlorosome was estimated according to models of BChl rod organisation. These calculations yielded upper limits ranging from 34 000 BChl molecules in Chl. vibrioforme to 240 000 in Chl. phaeobacteroides, values that greatly surpass those conventionally accepted.
利用原子力显微镜（AFM）对几种丝状无氧光合细菌（FAPB）和绿硫细菌（GSB）的分离叶绿体进行了检测，以表征其形貌和生物特征。橙色绿屈挠菌、绿线菌属和嗜温绿菌的叶绿体表面光滑，而噬纤维菌属绿菌和弧状绿菌的叶绿体表面粗糙。当比较AFM图像和透射电子显微镜图像时，排除了由于样品处理或AFM处理可能产生的两种表面的潜在人为性质。表面纹理的差异可能与叶绿体包膜的特定脂质和多肽组成有关。对三维AFM图像的研究还提供了有关单个叶绿体大小和形状的信息。弧状绿菌和噬纤维菌属绿菌的叶绿体体积分别约为35000 nm³至247000 nm³。除弧状绿菌（其高度仅为14 nm）外，所有研究物种的平均高度约为25 nm，这表明GSB有1 - 2层细菌叶绿素（BChl）棒，而GFB约有4层。此外，根据BChl棒组织模型估计了每个叶绿体中BChl分子的平均数量。这些计算得出的上限范围从弧状绿菌中的34000个BChl分子到噬纤维菌属绿菌中的240000个，这些值大大超过了传统接受的值。
