Molecular Mechanisms Of Variation And Adaptation In Borr

莱姆病的病原体伯氏疏螺旋体通过野生哺乳动物和蜱之间的感染循环在自然界中维持。像许多细菌病原体一样，B。伯氏菌必须应对一系列不断变化的环境条件，才能成功地持续存在、增殖并在宿主之间传播。我们的主要目标是利用分子遗传学方法阐明B适应和变异的分子机制。Burgdorferi及其在传染循环中的作用。B。Burgdorferi在硬蜱的自然生命周期的重要部分中存在于硬蜱的中肠中。蜱虫载体经历了许多生理和代谢变化，常驻细菌暴露于这些变化。在进食和准备蜕皮期间，硬蜱体表的扩张需要合成新的角质层，其中甲壳素是N-乙酰葡糖胺的聚合物。B的基因组序列。burgdorferi揭示了几种可能促进细菌利用几丁质副产物的基因，包括几丁质二糖（几丁质的二聚体亚基）转运蛋白的同源物。我们已经开始了一项研究，以确定这些基因产物是否有利于壳二糖的利用，并有助于蜱中的细菌生长。我们发现，壳二糖有效地取代N-乙酰氨基葡萄糖在培养基中的细菌生长。我们失活了编码转运蛋白跨膜成分的基因，并确定这些突变细菌无法利用壳二糖。我们还发现，转运蛋白基因的调节响应生长温度，与以前的结果表明温度作为一个重要的环境变量调节蜱和哺乳动物之间的差异基因表达一致。B几丁二糖利用遗传及调控的初步研究。用减毒的非致病性克隆进行伯氏螺旋体感染。我们最近在一个感染性克隆中灭活了壳二糖转运蛋白。我们已经开始了一系列的实验，以比较突变体和补充形式与其同基因野生型亲本在自然鼠蜱感染周期。直到最近，由于我们在致病性B的遗传操作方面取得了进展，这样的实验才成为可能。burgdorferi。

Borrelia burgdorferi, the causative agent of Lyme disease, is maintained in nature through an infectious cycle between wild mammals and ticks. Like many bacterial pathogens, B. burgdorferi must cope with an array of changing environmental conditions to successfully persist, proliferate and be transmitted between hosts. Our broad objective is to use a molecular genetic approach to elucidate the molecular mechanisms of adaptation and variation in B. burgdorferi and their roles in the infectious cycle. B. burgdorferi resides in the midgut of an ixodid tick for a significant part of its natural life cycle. The tick vector undergoes a number of physiological and metabolic changes to which resident bacteria are exposed. Expansion of the ixodid tick integument during feeding and preparation for molting requires the synthesis of new cuticle, of which chitin, a polymer of N-acetyl glucosamine, is a component. The genome sequence of B. burgdorferi revealed several genes likely to facilitate chitin by-product utilization by the bacteria, including homologs of a transporter for chitobiose (the dimer subunit of chitin). We have begun a study to determine if these gene products facilitate chitobiose utilization and contribute to bacterial growth in ticks. We found that chitobiose efficiently substitutes for N-acetyl glucosamine during bacterial growth in culture medium. We inactivated the gene encoding the membrane - spanning component of the transporter and determined that these mutant bacteria were unable to utilize chitobiose. We also found that the transporter gene was regulated in response to growth temperature, consistent with previous results demonstrating temperature as an important environmental variable regulating differential gene expression between ticks and mammals. Initial studies on the genetics and regulation of chitobiose utilization in B. burgdorferi were conducted with an attenuated, nonpathogenic clone. We have recently inactivated the chitobiose transporter in an infectious clone. We have begun a series of experiments to compare the mutant and complemented form with its isogenic wild type parent in the natural mouse-tick infectious cycle. Such experiments have only recently become possible because of advances we have made in the genetic manipulation of pathogenic B. burgdorferi.