Low temperature survival of Borrelia burgdorferi in overwintering ticks

描述（由申请人提供）：伯氏疏螺旋体是导致莱姆病的螺旋体，当被感染的蜱虫叮咬传播时，会引起人类疾病。伊蚊以受感染的哺乳动物为食的幼虫获得伯氏疏螺旋体；伯氏疏螺旋体在蜱虫的中肠中存活整个冬天。幼虫在春季蜕皮成若虫，成为将伯氏疏螺旋体传播给人类的媒介。该项目的长期目标是确定伯氏疏螺旋体在冬季低温环境中生存的分子机制。揭示这些生存策略完成了该机构的使命，因为拟议的实验将阐明该病原体的关键生物学特性，并为降低蜱虫若虫的伯氏疏螺旋体活力提供潜在靶点，从而降低人类感染的可能性。要验证的假设是MalQ，那么？-葡聚糖转移酶，产生低温保护剂双糖，这是伯氏疏螺旋体在低温下存活和在蜱虫中过冬所必需的。这一假设将在具体的目标1实验解决。第一个目标是研究诱导malQ转录和蛋白表达的条件。假设低温以及可能与蜱相关的因素会诱导malQ的表达。第二个目标是确定伯氏疏螺旋体是否产生海藻糖，以及生产是否依赖于malQ。第三个目标是确定伯氏疏螺旋体在低温下的存活是否依赖于malq。第四个也是最后一个目标是检查伯氏疏螺旋体在低温下在肩胛骨伊蚊中的存活是否依赖于malq。通过基因筛选确定与低温存活有关的其他因素将是特定Aim 2的重点。为了实现这一目标，将使用适用于伯氏疏螺旋体的mariner转座子系统使标记突变的基因组饱和。低温生长试验将识别生存受到损害的突变体。被转座子破坏的基因将被识别出来，从而与低温下的生长和蜱虫越冬媒介的存活有关。

DESCRIPTION (provided by applicant): Borrelia burgdorferi, the spirochete responsible for Lyme borreliosis, causes disease in humans when transmitted by the bite of infected Ixodes ticks. Ixodes acquire B. burgdorferi as larvae feed on infected mammals; B. burgdorferi survive in the tick midgut over winter. The larvae molt into nymphs in the spring to emerge as the vector that transmits B. burgdorferi to humans. The long-term goal of this project is to determine the molecular mechanisms that B. burgdorferi employ to survive the low temperatures in the tick during winter. Uncovering these survival strategies fulfills the mission of the agency as the proposed experiments will elucidate a key biological property of this pathogen and provide potential targets to reduce B. burgdorferi viability in tick nymphs, and thus reducing the likelihood of human infection. The hypothesis to be tested is that MalQ, an ?-glucanotransferase, produces cryoprotectant disaccharides that are essential for B. burgdorferi to survive at low temperatures and persist in ticks over winter. This hypothesis will be experimentally addressed in specific Aim 1. The first goal will examine the conditions that induce malQ transcript and protein expression. The hypothesis is that low temperature, and possibly tick-related factors, will induce malQ expression. The second goal will be to determine if B. burgdorferi produces trehalose and if production is dependent on malQ. The third goal will be to determine if B. burgdorferi survival at low temperature is malQ-dependent. The fourth and final goals are to examine if B. burgdorferi survival in Ixodes scapularis at low temperature is malQ-dependent. A genetic screen to identify additional factors involved in survival at low temperatures will be the focus of specific Aim 2. To accomplish this aim, the mariner transposon system adapted for B. burgdorferi will be used to saturate the genome with marked mutations. Low temperature growth assays will identify mutants whose survival has been compromised. Genes that have been disrupted by the transposon will be identified and, thus, implicated in growth at low temperatures and survival in the overwintering tick vector. PUBLIC HEALTH RELEVANCE: The incidence of Lyme borreliosis has steadily increased over the past 15 years with over 27,000 new cases reported in the United States in 2007. B. burgdorferi, the causative agent of Lyme disease, resides in the tick midgut throughout the tick's two year life cycle and is transmitted to humans by tick bite. By studying how B. burgdorferi overwinters in the tick we hope to uncover the molecular mechanisms that allow this bacterium to survive at low temperatures and emerge each summer as a problematic human pathogen.