Decreased infectivity in Borrelia burgdorferi strain B31 is associated with loss of linear plasmid 25 or 28-1
Decreased infectivity in Borrelia burgdorferi strain B31 is associated with loss of linear plasmid 25 or 28-1
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DOI：
10.1128/iai.69.1.446-455.2001
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发表时间：
2001-01-01
影响因子：
3.1
通讯作者：
Skare, JT
中科院分区：
文献类型：
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作者：
Labandeira-Rey, M;Skare, JT
先前的报道表明，质粒丢失与伯氏疏螺旋体B31菌株的感染性降低之间存在相关性，这提示质粒可能编码致病所需的蛋白质。在本研究中，我们进一步探究了这种相关性。利用伯氏疏螺旋体的基因组序列，我们为每个质粒设计了特异性引物，并通过聚合酶链反应（PCR）对来自传代中期的伯氏疏螺旋体B31菌株（最初源自感染小鼠的皮肤）的49个克隆分离株以及从感染低传代伯氏疏螺旋体B31菌株的小鼠皮肤中获得的20个克隆中的11个线性质粒和2个环形质粒进行了分类。在分析的69个克隆中，相对于野生型伯氏疏螺旋体B31菌株，鉴定出了9种不同的基因型。在获得的9种克隆基因型中，只有9 - kb环形质粒（cp9）、25 - kb线性质粒（lp25）以及28 - kb线性质粒1或4（分别为lp28 - 1和lp28 - 4）以不同组合缺失。我们比较了含有所有已知伯氏疏螺旋体质粒的野生型菌株与缺失lp28 - 1、lp28 - 4或lp25的单突变体以及缺失cp9和lp28 - 1的双突变体的感染性。感染性数据表明，缺失lp28 - 4的伯氏疏螺旋体B31细胞在所有分析的组织中感染性略有减弱，而缺失lp25的样本在所有组织中即使在最高接种量下也完全丧失感染性。不含lp28 - 1的分离株能够感染关节组织，但不能有效地感染其他组织。此外，我们观察到在皮肤、膀胱和关节中体内存在对含有lp25的细胞的选择，在皮肤和膀胱中存在对含有lp28 - 1的细胞的选择，这表明lp25和lp28 - 1编码在这些哺乳动物组织中定植和短期维持所需的蛋白质。相反，在关节中不存在对含有lp28 - 1的细胞的选择，这表明lp28 - 1上的基因对于伯氏疏螺旋体在关节内的定植不是必需的。这些观察结果意味着伯氏疏螺旋体基因组的动态特性可能为该病原体在自然界所处的不同环境中生存提供必要的遗传异质性，并可能有助于其在某些哺乳动物宿主组织中的嗜性。
Previous reports indicated a correlation between loss of plasmids and decreased infectivity of Borrelia burgdorferi strain B31, suggesting that plasmids may encode proteins that are required for pathogenesis. In this study, we expand on this correlation. Using the B. burgdorferi genomic sequence, we designed primers specific for each plasmid, and by using PCR we catalogued 11 linear and 2 circular plasmids from 49 clonal isolates of a mid-passage B. burgdorferi strain B31, initially derived from infected mouse skin, and 20 clones obtained from mouse skin infected with a low-passage isolate of B. burgdorferi strain B31. Among the 69 clones analyzed, nine distinct genotypes were identified relative to wild-type B. burgdorferi strain B31. Among the nine clonal genotypes obtained, only the 9-kb circular plasmid (cp9), the 25-kb linear plasmid (1p25), and either the 28-kb linear plasmid 1 or 4 (1p28-1 and 1p28-4, respectively) were missing, in different combinations. We compared the infectivity of the wild-type strain, containing all known B. burgdorferi plasmids, with those of single mutants lacking either 1p28-1, 1p28-4, or 1p25 and a double mutant missing both cp9 and 1p28-1, The infectivity data indicated that B. burgdorferi strain B31 cells tacking 1p28-4 were modestly attenuated in all tissues analyzed, whereas samples missing 1p25 were completely attenuated in all tissues, even at the highest inoculum tested. Isolates without 1p28-1 infected the joint tissue yet were not able to infect other tissues as effectively. In addition, we have observed a selection in vivo in the skin, bladder, and joint for cells containing 1p25 and in the skin and bladder for cells containing 1p28-1, indicating that 1p25 and 1p28-1 encode proteins required for colonization and short-term maintenance in these mammalian tissues. In contrast, there was no selection in the joint for cells containing 1p28-1, suggesting that genes on 1p28-1 are not required for colonization of B. burgdorferi within the joint. These observations imply that the dynamic nature of the B. burgdorferi genome may provide the genetic heterogeneity necessary for survival in the diverse milieus that this pathogen occupies in nature and may contribute to tropism in certain mammalian host tissues.