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

我的研究计划的长期目标是了解允许细菌适应营养限制的基本机制。铁是许多细胞过程的关键成分，包括DNA复制和氧代谢，也是许多细胞反应的辅因子。在革兰氏阴性肺炎克雷伯菌中，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，确定了在感染期间炎症、细菌传播和缺氧诱导因子1a稳定中的作用。然而，在蛋白质水平上，不同铁浓度的影响还没有很好地确定。最近，我们发现铁供应的变化会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作用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相关的蛋白质(例如cAMP受体和激酶)、细菌细胞黏附(例如脂蛋白)、多糖被膜产生(例如胶囊出口蛋白)、酶活性(例如蛋白酶)和动态平衡(例如转录因子)。此外，铁的存在或不存在会影响蛋白质(如Lon蛋白酶)的破坏，从而调节细菌的生长、包膜和铁的利用。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不同影响，但关于铁直接(通过转运体或铁载体)或间接(通过转录调节因子、信号级联)影响细菌生存的机制仍有许多问题。最重要的假设是肺炎克雷伯氏菌改变其蛋白质组，以响应铁浓度的变化来调节一系列不同的细胞过程，以促进其生存。在这项建议中，我将重点讨论肺炎克雷伯菌中铁的可利用性与I)信号转导途径、II)酶的产生和III)一般应激反应之间的关系。在接下来的5年里，我的研究计划将对铁在肺炎克雷伯菌中的不同作用提供新的见解，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，适用于不同的生物系统(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).