Institute of Immunology, College of Veterinary Medicine, and Center for Biotechnology and Biomedicine, University of Leipzig, Germany.
J Basic Microbiol. 2010 Dec;50 Suppl 1:S5-17. doi: 10.1002/jobm.201000074.
Borrelia burgdorferi, the agent of Lyme borreliosis, has the ability to undergo morphological transformation from a motile spirochetal to non-motile spherical shape when it encounters unfavorable conditions. However, little information is available on the mechanism that enables the bacterium to change its shape and whether major components of the cells--nucleic acids, proteins, lipids--are possibly modified during the process. Deducing from investigations utilizing electron microscopy, it seems that shape alteration begins with membrane budding followed by folding of the protoplasmatic cylinder inside the outer surface membrane. Scanning electron microscopy confirmed that a deficiency in producing functioning periplasmic flagella did not hinder sphere formation. Further, it was shown that the spirochetes' and spheres' lipid compositions were indistinguishable. Neither phosphatidylcholine nor phosphatidylglycerol were altered by the structural transformation. In addition, no changes in differential protein expression were detected during this process. However, minimal degradation of RNA and a reduced antigen-antibody binding activity were observed with advanced age of the spheres. The results of our comparisons and the failure to generate mutants lacking the ability to convert to spheres suggest that the metamorphosis of B. burgdorferi results in a conditional reconstruction of the outer membrane. The spheres, which appear to be more resistant to unfavorable conditions and exhibit reduced immune reactivity when compared to spirochetes, might allow the B. burgdorferi to escape complete clearance and possibly ensure long-term survival in the host.
伯氏疏螺旋体是莱姆病的病原体，当遇到不利条件时，它有能力从运动的螺旋体形态转变为非运动的球形。然而，对于使细菌能够改变其形状的机制以及细胞的主要成分（核酸、蛋白质、脂质）是否在该过程中可能发生修饰，知之甚少。从利用电子显微镜进行的研究中推断，形态改变似乎始于膜出芽，随后在外膜内的原生质圆柱体折叠。扫描电子显微镜证实，产生功能型周质鞭毛的缺陷并不妨碍球体的形成。此外，还表明螺旋体和球体的脂质组成无法区分。结构转换没有改变磷脂酰胆碱或磷脂酰甘油。此外，在此过程中未检测到差异蛋白表达的变化。然而，随着球体年龄的增加，观察到 RNA 的最小降解和抗原-抗体结合活性降低。我们的比较结果以及未能产生无法转化为球体的突变体表明，伯氏疏螺旋体的形态发生导致了外膜的条件性重建。与螺旋体相比，球体似乎对不利条件更具抵抗力，免疫反应性降低，这可能使伯氏疏螺旋体逃脱完全清除，并可能确保在宿主中长期存活。
