Defining the systems-level impact of iron limitation in Klebsiella pneumoniae

我的研究项目的长期目标是了解细菌适应营养限制的基本机制。铁是许多细胞过程的重要组成部分，包括DNA复制和氧代谢，以及许多细胞反应的辅助因子。在肺炎克雷伯菌（一种革兰氏阴性、被包裹的细菌）中，铁的作用及其对铁载体表达的影响最近在转录水平上进行了研究，确定了感染期间炎症、细菌传播和缺氧诱导因子1a稳定的作用。然而，在蛋白质水平上，可变铁浓度的影响尚未得到很好的定义。最近，我们发现铁可用性的变化影响肺炎克雷伯菌的细胞蛋白质组和分泌组。我们对铁在肺炎克雷伯菌中的作用进行的蛋白质组学研究揭示了多种蛋白质的调节，包括与信号转导途径（如cAMP受体和激酶）、细菌细胞粘附（如脂蛋白）、多糖胶囊生产（如胶囊输出蛋白）、酶活性（如蛋白酶）和稳态（如转录因子）相关的蛋白质。此外，受铁的存在或不存在影响的蛋白质（如Lon蛋白酶）的破坏可调节细菌的生长、囊化和铁的利用。我们的工作已经开始揭示铁对肺炎克雷伯菌细胞过程和调控的多种影响，但关于铁直接（通过转运体或铁载体）或间接（通过转录调节剂，信号级联）影响细菌存活的机制仍然存在许多问题。总体假设是肺炎克雷伯菌改变其蛋白质组以响应铁浓度的变化，从而调节多种细胞过程以促进其生存。对于本提案，我将重点关注肺炎克雷伯菌铁可用性与I)信号转导途径，ii)酶生产和iii)一般应激反应调节之间的联系。在接下来的5年里，我的研究计划将为铁在肺炎克雷伯菌中的多种作用提供新的见解，并定义强调细菌适应性的生物学机制。这项工作对我们理解细菌对铁的反应具有重要意义，我们的发现以及所使用的方法将超越原核细胞生物学，并适用于各种生物系统（例如真菌物种）。

The long-term goal of my research program is to understand fundamental mechanisms that allow bacteria to adapt to nutrient limitation. Iron is a critical component of many cellular processes, including DNA replication and oxygen metabolism, as well as a cofactor for many cellular reactions. In Klebsiella pneumoniae, a Gram--negative, encapsulated bacterium, the role of iron and its influence on siderophore expression was recently studied at the transcriptional level, defining a role in inflammation, bacterial dissemination, and hypoxia -inducible factor 1a stabilization during infection. However, at the protein level, the effect of variable iron concentrations has not been well defined. Recently, we discovered that changes in iron availability impact the cellular proteome and secretome of K. pneumoniae. Our proteomic investigation into the role of iron in K. pneumoniae uncovered modulation of a variety of proteins, including those associated with signal transduction pathways (e.g., cAMP receptor and kinases), bacterial cell adhesion (e.g., lipoproteins), polysaccharide capsule production (e.g, capsule export protein), enzymatic activity (e.g., proteases), and homeostasis (e.g., transcription factors). Moreover, disruption of proteins (e.g., Lon protease) influenced by the presence or absence of iron modulate bacterial growth, capsule, and iron utilization. Our work has begun to uncover the diverse impact of iron on cellular processes and regulation in K. pneumoniae, but many questions remain regarding the mechanisms by which iron directly (via transporters or siderophores) or indirectly (via transcriptional regulators, signaling cascades) influences bacterial survival. The overarching hypothesis is that K. pneumoniae alters its proteome in response to changing iron concentrations to modulate a diverse array of cellular processes to promote its survival. For this proposal, I will focus on the connection between iron availability in K. pneumoniae and the regulation of i) signal transduction pathways, ii) enzyme production, and iii) general stress response. Over the next 5 years, my research program will provide novel insight into the diverse role of iron in K. pneumoniae and define the biological mechanisms that underscore bacterial adaptability. This work has important implications for our understanding of the bacterial response to iron, and our findings, along with the approaches used, will transcend prokaryotic cell biology and be applicable to diverse biological systems (e.g., fungal species).