Antimicrobial activity of Escherichia coli Nissle 1917 microcin M

总结 肠杆菌科是革兰氏阴性菌的一个家族，既包含细菌又包含病原体 与人类健康有关。其中最突出的病原体是非伤寒沙门氏菌 肠杆菌是全球感染性腹泻的主要原因。这种病原体成功的关键在于它能够 肠道炎症，这是一种宿主反应，它创造了一个不利的肠道环境，许多寄生虫在那里生长。 耗尽，但沙门氏菌蓬勃发展，显着增加丰度。在感染过程中，病原体必须 获得必需的金属营养素，如铁，一种受宿主高度限制的元素。在初步研究中， 我们发现益生菌大肠杆菌Nissle 1917可以与沙门氏菌和其他肠道菌竞争， 病原体在发炎的肠道产生抗菌肽称为微菌素。特别是，我们发现， 沙门氏菌在铁限制条件下和发炎的肠道中对微菌素M敏感。主要目的 本申请的目的是阐明E.大肠杆菌Nissle’s microcin M（MccM）的体外和 vivo.我们的中心假设是，结合儿茶酚铁载体，使MccM更有选择性地 靶向细菌，在Fe限制的宿主环境中表达特异性铁载体受体，而不影响 肠道微生物群。我们计划测试我们的假设，并通过以下方式实现本申请的目标 有以下两个具体目标。在目标1中，我们将确定铁载体结合和铁载体是否 摄取机制影响MccM的抗菌活性，我们将确定MccM的假定细胞靶点。 MccM活性通过筛选突变体库。研究MccM选择性的潜在机制 抗菌活性在目标2中，我们将确定MccM对非伤寒的抗菌活性 沙门氏菌在体内，我们将确定是否管理纯化MccM扰乱肠道 这项工作可能会导致微菌素作为治疗剂的未来发展，以限制定植， 非伤寒沙门氏菌的传播，以及可能的其他肠道病原体和致病菌， 这是一个有利于他们成长的环境。

SUMMARY Enterobacteriaceae are a family of Gram-negative bacteria that contains both commensals and pathogens relevant to human health. Among the most prominent pathogens of this family is non-typhoidal Salmonella enterica, a leading cause of infectious diarrhea worldwide. Key to this pathogen's success is its ability to elicit intestinal inflammation, a host response that creates a hostile gut environment where many commensals are depleted, but where Salmonella thrives, significantly increasing in abundance. During infection, pathogens must acquire essential metal nutrients such as iron, an element that is highly limited by the host. In preliminary studies, we found that the probiotic bacterium Escherichia coli Nissle 1917 can compete with Salmonella and other enteric pathogens in the inflamed gut by producing antibacterial peptides termed microcins. In particular, we found that Salmonella is susceptible to microcin M in iron-limited conditions and in the inflamed gut. The primary objective of this application is to elucidate the antimicrobial activity of E. coli Nissle's microcin M (MccM) in vitro and in vivo. Our central hypothesis is that conjugation to catecholate siderophores enables MccM to more selectively target bacteria that express specific siderophore receptors in the Fe-limited host environment, without affecting the gut microbiota at large. We plan to test our hypothesis and fulfill the objectives of this application by pursuing the following two Specific Aims. In Aim 1, we will determine whether siderophore conjugation and siderophore uptake machinery influences the antimicrobial activity of MccM, and we will identify putative cellular targets of MccM activity by screening mutant libraries. Investigate the mechanisms underlying the selectivity of MccM antimicrobial activity. In Aim 2, we will ascertain the antimicrobial activity of MccM against non-typhoidal Salmonella in vivo, and we will determine whether administration of purified MccM perturbs the gut microbiome.This work may lead to future development of microcins as therapeutics to limit colonization and transmission of non-typhoidal Salmonella, and possibly other enteric pathogens and pathobionts, in an environment that is otherwise favorable to their growth.