Sodalis glossinidius iron acquisition

描述（由申请人提供）：舌蝇是一种兼性细胞内细菌，是采采蝇的次级共生体，采采蝇携带引起非洲昏睡病的锥虫。尽管自20世纪80年代中期以来，采采蝇细胞内存在Sodalis已被记录，但使这种兼性内共生细菌在采采蝇和细胞内环境中存活和繁殖的生理过程才刚刚开始被研究。研究这些过程将有助于pi研究的长期科学目标，即确定兼性细胞内细菌在宿主体内生存和/或繁殖的代谢和生理过程，以及在这些环境中调节基因表达的因素。这个项目的科学目标是测试假设的Sodalis铁获取系统对昆虫细胞和采采蝇内Sodalis生长的贡献。据预测，一个系统（HemR/HemTUV）编码转运蛋白，介导血红素作为铁源的获取。由于采采蝇的血在中肠中被消化，释放出游离的血红素，因此在中肠组织中居住的梭菌应该很容易获得血红素。第二个系统被预测为编码一个调节高亲和力铁获取的消动蛋白铁载体系统。当索达利在采采蝇细胞内和/或在游离铁量有限的其他环境中，该系统可能很重要。在具体目标1和2中，将研究Sodalis血红素和色素移动蛋白转运体突变体在采采蝇和昆虫培养中生长的能力，以检验与Sodalis铁获取基因对Sodalis在这些环境中生长重要的问题相关的假设。在Specific Aim 3中，将通过分析Sodalis血红素和血红蛋白转运体突变体在以血红素或铁-血红蛋白作为唯一铁源的培养基中的生长情况，以及在不能以血红素或血红蛋白作为铁源的异源菌株中重构Sodalis系统，来评估推测的Sodalis血红素和血红蛋白转运体的功能。研究采采蝇与线虫的共生关系对公共卫生具有重要意义。采采蝇中Sodalis的存在可能会增加采采蝇介导的锥虫传播，最近的研究表明，副转化可能是控制非洲锥虫病的一种有用策略。由于这些原因，更全面地了解梭菌与采采蝇共生的性质将有助于控制采采蝇传播的疾病。

DESCRIPTION (provided by applicant): Sodalis glossinidius is a facultative intracellular bacterium that is a secondary symbiont of the tsetse fly, which carries the trypanosome that causes African sleeping sickness. Although the presence of Sodalis within the cells of the tsetse fly has been documented since the mid-1980s, the physiological processes that enable this facultative endosymbiotic bacterium to survive and multiply within the tsetse fly and the intracellular environment are just beginning to be examined. Investigating these processes will contribute to the long-term scientific goals of the PIs research, which are to identify the metabolic and physiological processes that facultative intracellular bacteria employ to survive and/or multiply within their hosts, as well as the elements that regulate gene expression in these environments. The scientific goals of this project are to test hypotheses which address the contribution of putative Sodalis iron acquisition systems to growth of Sodalis within insect cells and the tsetse fly. One system (HemR/HemTUV) is predicted to encode transport proteins that mediate acquisition of heme as an iron source. Heme should be readily available to Sodalis residing in midgut tissue since the tsetse fly blood meal is digested in the midgut to release free heme. The second system is predicted to encode an achromobactin siderophore system that mediates high affinity iron acquisition. This system may be important when Sodalis is within the tsetse fly cells and/or in other environments where free iron is in limiting quantities. In Specific Aims 1 and 2, the ability of the Sodalis heme and achromobactin transporter mutants to grow in tsetse flies and in insect culture will be examined to test hypotheses related to the question of which Sodalis iron acquisition genes are important for growth of Sodalis in these environments. In Specific Aim 3, the function of the putative Sodalis heme and achromobactin transporters will be assessed by analyzing growth of the Sodalis heme and achromobactin transporter mutants in media with either heme or ferri- achromobactin as a sole iron source and by reconstituting the Sodalis systems in heterologous bacterial strains that cannot use heme or achromobactin as iron sources. Studying the tsetse fly-Sodalis symbiosis will have significance to public health. The presence of Sodalis in the tsetse fly may increase tsetse-mediated transmission of the trypanosome, and recent research suggests that paratransgenesis may be a useful control strategy for African trypanosomiasis. For these reasons, a more complete understanding of the nature of the Sodalis-tsetse symbiosis will yield information to help control tsetse-borne disease. PUBLIC HEALTH RELEVANCE: Tsetse-transmitted trypanosomiasis represents a significant global health burden, threatening millions of people in sub-Saharan Africa. Since the presence of Sodalis in the tsetse fly may increase tsetse-mediated transmission of the trypanosome and since recent research suggests that modifying Sodalis glossinidius (one of the bacterial species harbored by the tsetse fly) may be a useful control strategy for African trypanosomiasis, a more complete understanding of the nature of the Sodalis-tsetse symbiosis will yield information to help control tsetse-borne disease. Finally, because Sodalis is one of only a few intracellular insect symbionts to be cultured outside of the host, it can be developed as a model for the study of other intracellular insect symbionts that have an impact on the ability of the insect to transmit disease.