Evolution and Distribution of the ospC Gene, a Transferable Serotype Determinant of Borrelia burgdorferi
Evolution and Distribution of the ospC Gene, a Transferable Serotype Determinant of Borrelia burgdorferi
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DOI：
10.1128/mbio.00153-10
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发表时间：
2010-09-01
期刊：
影响因子：
6.4
通讯作者：
Travinsky, Bridgit
中科院分区：
文献类型：
--
作者：
Barbour, Alan G.;Travinsky, Bridgit
伯氏疏螺旋体是一种新出现的细菌病原体，在自然界中是通过扁虱从一个脊椎动物宿主传播到另一个宿主而维持的。哺乳动物产生保护性免疫的为数不多的抗原之一是高度多态的OspC蛋白，它由cp26质粒上的OspC基因编码。OspC基因之间的基因内重组是已知的，但重组延伸到OspC基因之外的程度还不确定。我们访问并补充了来自美国三个地区(东北部、中西部和加利福尼亚州北部)扁虱的OspC和其他基因座的DNA序列；总共分析了839个OspC序列。三个重叠但不同的伯氏杆菌种群与地理区域相对应。此外，我们还对来自不同谱系的99个OspC侧翼序列进行了测序，并比较了11个菌株的cp26全序列以及56个样本的cp26 bbb02基因座。除了仅限于OspC基因本身的重组外，还有证据表明，横向基因转移涉及(I)OspC基因的一部分和两侧之一，或(Ii)整个OspC基因和不同长度的两侧。横向基因转移导致OspC基因与染色体或其他质粒的基因座之间的不同连锁。通过获得新的OspC基因的全部或很大部分，其他适应株将具有新的血清型特征，从而在对现有OspC类型免疫力较高的地区相对更适合。进一步了解伯氏疏螺旋体在其环境中的进化和遗传学，有助于在基于生态的控制努力方面取得进展。通过对来自美国各地的病原体的大量样本进行DNA测序，我们研究了该细菌高度多样化的OspC蛋白的基因，该蛋白对动物产生的保护性免疫。我们发现，在东北、中西部和加利福尼亚州的伯氏杆菌种群中，OspC基因类型的分布和频率不同。随着时间的推移，OspC基因通过涉及整个或部分基因以及一个或两个侧翼的重组在菌株之间转移。获得该区域新的OspC基因赋予受体对宿主免疫系统的独特身份，并在对现有类型的免疫在宿主中普遍存在的情况下可能具有选择性优势。
Borrelia burgdorferi, an emerging bacterial pathogen, is maintained in nature by transmission from one vertebrate host to another by ticks. One of the few antigens against which mammals develop protective immunity is the highly polymorphic OspC protein, encoded by the ospC gene on the cp26 plasmid. Intragenic recombination among ospC genes is known, but the extent to which recombination extended beyond the ospC locus itself is undefined. We accessed and supplemented collections of DNA sequences of ospC and other loci from ticks in three U. S. regions (the Northeast, the Midwest, and northern California); a total of 839 ospC sequences were analyzed. Three overlapping but distinct populations of B. burgdorferi corresponded to the geographic regions. In addition, we sequenced 99 ospC flanking sequences from different lineages and compared the complete cp26 sequences of 11 strains as well as the cp26 bbb02 loci of 56 samples. Besides recombinations with traces limited to the ospC gene itself, there was evidence of lateral gene transfers that involved (i) part of the ospC gene and one of the two flanks or (ii) the entire ospC gene and different lengths of both flanks. Lateral gene transfers resulted in different linkages between the ospC gene and loci of the chromosome or other plasmids. By acquisition of the complete part or a large part of a novel ospC gene, an otherwise adapted strain would assume a new serotypic identity, thereby being comparatively fitter in an area with a high prevalence of immunity to existing OspC types.IMPORTANCE The tick-borne zoonosis Lyme borreliosis is increasing in incidence and spreading geospatially in North America. Further understanding of the evolution and genetics of its cause, Borrelia burgdorferi, in its environments fosters progress toward ecologically based control efforts. By means of DNA sequencing of a large sample collection of the pathogen from across the United States, we studied the gene for the bacterium's highly diverse OspC protein, protective immunity against which develops in animals. We found that the distributions and frequencies of types of OspC genes differed between populations of B. burgdorferi in the Northeast, the Midwest, and California. Over time, OspC genes were transferred between strains through recombinations involving the whole or parts of the gene and one or both flanks. Acquisitions of OspC genes that are novel for the region confer to recipients unique identities to host immune systems and, presumably, selective advantage when immunity to existing types is widespread among hosts.