Barbour A G
Department of Medicine, University of Texas Health Science Center, San Antonio, Texas 78284.
Rev Infect Dis. 1989 Sep-Oct;11 Suppl 6:S1470-4. doi: 10.1093/clinids/11.supplement_6.s1470.
Borrelia burgdorferi, the cause of Lyme disease, has two major outer-membrane proteins, OspA and OspB, which act as surface antigens. A 49-kilobase linear plasmid contains the genes that encode for these surface proteins. Direct examination of denatured plasmid molecules has revealed single-stranded circles with a circumference of approximately 100 kilobases (about twice the length of the linear duplex molecule), a finding that indicates the plasmid strands have covalently closed ends. This form of DNA, while present in eukaryotic organisms and their viruses, has not been observed in a prokaryotic organism. Plasmid heterogeneity has been observed in strains with surface proteins of similar molecular weights and similar monoclonal antibody reactivity. Thus, plasmid analysis may prove a sensitive tool for differentiating strains of B. burgdorferi. Furthermore, since loss of plasmids in vitro has been correlated with loss of the ability of many-passaged strains to cause infection, borrelial plasmids may encode for virulence factors as well.
莱姆病的病原体伯氏疏螺旋体有两种主要的外膜蛋白，即OspA和OspB，它们作为表面抗原起作用。一个49千碱基的线性质粒包含编码这些表面蛋白的基因。对变性质粒分子的直接检测发现了单链环，其周长约为100千碱基（约为线性双链分子长度的两倍），这一发现表明质粒链具有共价闭合末端。这种DNA形式虽然存在于真核生物及其病毒中，但在原核生物中尚未观察到。在具有相似分子量和相似单克隆抗体反应性的表面蛋白的菌株中观察到了质粒异质性。因此，质粒分析可能是区分伯氏疏螺旋体菌株的一种敏感工具。此外，由于体外质粒的丢失与多代培养菌株引起感染的能力丧失有关，伯氏疏螺旋体质粒可能也编码毒力因子。
