A bacterial biosensor for intracellular metal availability in the gut

项目摘要 在食源性细菌、原虫和病毒性疾病中，非伤寒性肠道沙门氏菌引起的疾病最多 全球疾病和死亡的负担。最常见的人类临床分离株是肠道沙门氏菌 血清型鼠伤寒沙门氏菌（S.鼠伤寒沙门氏菌，STm）和肠炎（S.肠炎）。感染可以导致自体- 限制性胃肠炎或危及生命的侵袭性疾病。肠内给药期间 感染时，STm采用细胞外和细胞内的生活方式，也在肠腔定植 肠粘膜上皮细胞和吞噬细胞。在这里，我们将研究如何主机介导的限制， 被称为营养免疫的过渡金属影响肠道的STm定殖。NRAMP家族 蛋白质是二价阳离子的“混杂”转运体， 在哺乳动物中，存在两个NRAMP基因，人中的SLC 11 A1和SLC 11 A2， 和Slc 11 a2。Slc 11 a1仅限于髓系，而Slc 11 a2广泛表达。 虽然Slc 11 a1在控制巨噬细胞和小鼠的细胞内细菌和寄生虫感染中的作用 尽管Slc 11 a2的抗菌功能是无可争议的，但Slc 11 a2是否也有助于抗菌功能尚不清楚。我们的一般假设 细胞内金属离子的可利用性在肠中的上皮细胞和吞噬细胞中不同， SLC 11 A1和SLC 11 A2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 浓度感染牛结扎回肠袢，一种高度相关的人类肠道沙门氏菌病模型， 绘制肠道中金属离子缺乏的时空分布图。第二，我们将确定 SLC 11 A2是唯一在肠上皮细胞中表达的NRAMP家族成员， 病原体通过金属营养限制。本提案的完成将填补以下方面的重大知识空白： 肠道感染期间肠道中宿主-微生物对金属离子的竞争。

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.