A bacterial biosensor for intracellular metal availability in the gut

项目总结 在食源性细菌性、原虫性和病毒性疾病中，非伤寒沙门氏菌引起的疾病最多 世界范围内疾病和死亡的负担。最常见的人类临床分离株是肠道沙门氏菌 小鼠伤寒沙门氏菌(STM)和肠炎(沙门氏菌肠炎)的血清型。感染可能会导致自身 局限性胃肠炎或免疫受损个体的一种危及生命的侵袭性疾病。在肠道中 感染，STM采取细胞外和细胞内的生活方式，也定植于肠腔 肠粘膜内的上皮细胞和吞噬细胞。在这里我们将研究宿主介导的限制是如何 过渡金属被称为营养免疫，会影响肠道中STM的定植。NRAMP家族 蛋白质是二价阳离子的“混杂”转运体，它在金属离子的动态平衡中起着重要作用。 细菌传给人类。在哺乳动物中，有两个NRAMP基因，人类的SLC11A1和SLC11A2，以及SLC11a1 和小鼠的SLc11a2。SLc11a1仅限于髓系，而slc11a2广泛表达。 而SLc11a1在控制巨噬细胞和小鼠细胞内细菌和寄生虫感染中的作用 毫无疑问，Slc11a2是否也具有抗菌功能尚不清楚。我们的一般假设 细胞内金属离子在肠道上皮细胞和吞噬细胞中的有效性不同是由于 SLC11A1和SLC11A2的细胞型表达。首先，我们将使用金属离子的微生物生物传感器 感染牛结扎回肠环的浓度，这是人类肠道沙门氏菌病的一种高度相关的模型， 并绘制出肠道内金属离子剥夺的时空分布。其次，我们将定义是否 SLC11A2是唯一在肠上皮细胞中表达的NRAMP家族成员，对入侵具有抵抗力 病原体通过金属营养限制。这项提议的完成将弥合关于以下方面的重大知识差距 肠道感染时宿主-微生物对肠道金属离子的竞争。

PROJECT SUMMARY Of the foodborne bacterial, protozoal and viral diseases, non-typhoidal Salmonella enterica cause the largest burden of illness and death worldwide. The most common human clinical isolates are Salmonella enterica serovars Typhimurium (S. Typhimurium, STm) and Enteriditis (S. Enteriditis). Infection can cause either a self- limiting gastroenteritis or a life-threatening, invasive disease in immunocompromised individuals. During enteric infection, STm adopts both extracellular and intracellular lifestyles, colonizing the intestinal lumen as well epithelial cells and phagocytes in the intestinal mucosa. Here we will study how host-mediated restriction of transition metals, known as nutritional immunity, affects STm colonization of the gut. The NRAMP family of proteins are “promiscuous” transporters of divalent cations that play a major role in metal ion homeostasis from bacteria to man. In mammals, there are two NRAMP genes, SLC11A1 and SLC11A2 in humans and Slc11a1 and Slc11a2 in mice. Slc11a1 is restricted to the myeloid lineage whereas Slc11a2 is ubiquitously expressed. Whilst the role of Slc11a1 in controlling intracellular bacterial and parasitic infections in macrophages and mice is undisputed, whether Slc11a2 also contributes to antimicrobial functions is unknown. Our general hypothesis is that intracellular metal ion availability differs in epithelial cells and phagocytes in the gut due to the distinct cell-type expression of SLC11A1 and SLC11A2. First, we will use microbial biosensors of metal ion concentrations to infect bovine ligated ileal loops, a highly relevant model of enteric salmonellosis in humans, and map the spatiotemporal distribution of metal ion deprivation in the gut. Second, we will define whether SLC11A2, the sole NRAMP family member expressed in intestinal epithelial cells, defends against invading pathogens via metal nutrient limitation. Completion of this proposal will close a significant knowledge gap about host-microbe competition for metal ions in the gut during enteric infection.