Walker E M, Zampighi G A, Blanco D R, Miller J N, Lovett M A
Department of Microbiology and Immunology, School of Medicine, University of California, Los Angeles 90024.
J Bacteriol. 1989 Sep;171(9):5005-11. doi: 10.1128/jb.171.9.5005-5011.1989.
The surface of Treponema pallidum subsp. pallidum (T. pallidum), the etiologic agent of syphilis, appears antigenically inert and lacks detectable protein, as judged by immunocytochemical and biochemical techniques commonly used to identify the outer membrane (OM) constituents of gram-negative bacteria. We examined T. pallidum by freeze-fracture electron microscopy to visualize the architecture of its OM. Treponema phagedenis biotype Reiter (T. phagedenis Reiter), a nonpathogenic host-associated treponeme, and Spirochaeta aurantia, a free-living spirochete, were studied similarly. Few intramembranous particles interrupted the smooth convex and concave fracture faces of the OM of T. pallidum, demonstrating that the OM of this organism is an unusual, nearly naked lipid bilayer. In contrast, the concave fracture face of the OM of S. aurantia was densely covered with particles, indicating the presence of abundant integral membrane proteins, a feature shared by typical gram-negative organisms. The concentration of particles in the OM concave fracture face of T. phagedenis Reiter was intermediate between those of T. pallidum and S. aurantia. Similar to typical gram-negative bacteria, the OM convex fracture faces of the three spirochetes contained relatively few particles. The unique molecular architecture of the OM of T. pallidum can explain the puzzling in vitro properties of the surface of the organism and may reflect a specific adaptation by which treponemes evade the host immune response.
梅毒的病原体梅毒螺旋体苍白亚种（T. pallidum）的表面，通过常用于鉴定革兰氏阴性菌外膜（OM）成分的免疫细胞化学和生化技术判断，似乎抗原性不活跃且缺乏可检测到的蛋白质。我们通过冷冻断裂电子显微镜检查T. pallidum，以观察其外膜的结构。类似地研究了非致病性宿主相关密螺旋体噬齿密螺旋体生物型赖特氏菌（T. phagedenis Reiter）和自由生活的螺旋体金色螺旋体（Spirochaeta aurantia）。很少有膜内颗粒打断T. pallidum外膜光滑的凸面和凹面断裂面，表明该生物体的外膜是一种不同寻常的、几乎裸露的脂质双层。相比之下，金色螺旋体外膜的凹面断裂面密集地覆盖着颗粒，表明存在丰富的整合膜蛋白，这是典型革兰氏阴性生物体共有的特征。赖特氏菌外膜凹面断裂面的颗粒浓度介于T. pallidum和金色螺旋体之间。与典型革兰氏阴性菌相似，三种螺旋体外膜的凸面断裂面含有的颗粒相对较少。T. pallidum外膜独特的分子结构可以解释该生物体表面令人困惑的体外特性，并且可能反映了密螺旋体逃避宿主免疫反应的一种特殊适应性。
