Muselius Benjamin, Sukumaran Arjun, Yeung Jason, Geddes-McAlister Jennifer
Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada.
Front Microbiol. 2020 Apr 24;11:546. doi: 10.3389/fmicb.2020.00546. eCollection 2020.
Nutrient adaptation is key in limiting environments for the promotion of microbial growth and survival. In microbial systems, iron is an essential component for many cellular processes, and bioavailability varies greatly among different conditions. In the bacterium, , the impact of iron limitation is known to alter transcriptional expression of iron-acquisition pathways and influence secretion of iron-binding siderophores, however, a comprehensive view of iron limitation at the protein level remains to be defined. Here, we apply a mass-spectrometry-based quantitative proteomics strategy to profile the global impact of iron limitation on the cellular proteome and extracellular environment (secretome) of . Our data define the impact of iron on proteins involved in transcriptional regulation and emphasize the modulation of a vast array of proteins associated with iron acquisition, transport, and binding. We also identify proteins in the extracellular environment associated with conventional and non-conventional modes of secretion, as well as vesicle release. In particular, we demonstrate a new role for Lon protease in promoting iron homeostasis outside of the cell. Characterization of a Lon protease mutant in validates roles in bacterial growth, cell division, and virulence, and uncovers novel degradation candidates of Lon protease associated with improved iron utilization strategies in the absence of the enzyme. Overall, we provide evidence of unique connections between Lon and iron in a bacterial system and suggest a new role for Lon protease in the extracellular environment during nutrient limitation.
在限制环境中，营养适应对于促进微生物生长和存活至关重要。在微生物系统中，铁是许多细胞过程的必需成分，其生物可利用性在不同条件下差异很大。在细菌中，已知铁限制的影响会改变铁获取途径的转录表达并影响铁结合铁载体的分泌，然而，在蛋白质水平上对铁限制的全面认识仍有待确定。在这里，我们应用基于质谱的定量蛋白质组学策略来剖析铁限制对细胞蛋白质组和细胞外环境（分泌组）的全局影响。我们的数据确定了铁对参与转录调控的蛋白质的影响，并强调了与铁获取、运输和结合相关的大量蛋白质的调节。我们还鉴定了细胞外环境中与传统和非传统分泌模式以及囊泡释放相关的蛋白质。特别是，我们证明了Lon蛋白酶在促进细胞外铁稳态方面的新作用。对Lon蛋白酶突变体的表征验证了其在细菌生长、细胞分裂和毒力中的作用，并揭示了在缺乏该酶的情况下与改善铁利用策略相关的Lon蛋白酶的新降解候选物。总体而言，我们提供了细菌系统中Lon与铁之间独特联系的证据，并提出了Lon蛋白酶在营养限制期间细胞外环境中的新作用。
