Metal ion homeostasis in Bacillus subtilis

描述（由申请人提供）：本提案研究模型革兰氏阳性杆菌枯草芽孢杆菌对金属离子饥饿的反应。当细胞缺乏必需的金属，如铁或锌时，它们会表达复杂的适应性反应。这些反应包括精心设计高亲和力吸收系统以从环境中获取金属。也许更重要的是，细胞重新编程了它们的新陈代谢，以阻止不需要的蛋白质和酶的合成，这些蛋白质和酶会消耗有限的营养。在铁的情况下，这种“铁节约反应”导致细胞蛋白质组成和代谢潜力的大规模变化，并对细胞生理学产生广泛的影响。铁保留反应在各种生物体中已经进化了多次，并由各种基于RNA和蛋白质的调节因子介导。在枯草芽孢杆菌中，铁节约反应需要一个调节的小RNA，它与三个编码小的基本肽的基因协同工作。这些小蛋白质被认为至少部分地起着RNA伴侣的作用。初步结果表明，对锌饥饿的反应也是复杂和多方面的。抑制非必需锌金属蛋白的合成提供了一种“锌保留反应”，一组替代核糖体蛋白的表达取代了核糖体中含有锌的小肽，为细胞提供锌。除了表达高亲和力的金属离子摄取（获取）和抑制非必需金属蛋白（保留）外，细胞还表达替代同工酶，以实现一些可能被破坏的基本功能（替代）。本提案将侧重于这些特征和相关的适应性反应，使细胞即使在严重金属限制的环境中也能有效地竞争。金属离子是生命所必需的，是许多酶和电子转移过程的辅助因子。本提案旨在了解模型革兰氏阳性杆菌枯草芽孢杆菌如何适应铁和锌的限制。这些研究将为革兰氏阳性病原体（如金黄色葡萄球菌、链球菌和肠球菌）在宿主体内金属受限的环境中生存的适应过程提供重要的见解。

DESCRIPTION (provided by applicant): This proposal investigates the responses of the model Gram positive bacterium Bacillus subtilis to metal ion starvation. When cells are starved for essential metals, such as iron or zinc, they express complex adaptive responses. These responses include the elaboration of high affinity uptake systems to obtain metals from the environment. Perhaps even more important, cells reprogram their metabolism to block the synthesis of unneeded proteins and enzymes that will consume the limiting nutrient. In the case of iron, this "iron-sparing response" leads to large scale changes in the protein composition and metabolic potential of the cell and has wide-ranging ramifications for cell physiology. Iron-sparing responses have evolved multiple times in various organisms and are mediated by a variety of RNA- and protein-based regulators. In B. subtilis, the iron-sparing response requires a regulatory, small RNA that functions in collaboration with three genes encoding small, basic peptides. These small proteins are postulated to function, at least in part, as RNA chaperones. Preliminary results suggest that the response to zinc starvation is also complex and multifaceted. Repression of the synthesis of non-essential zinc metalloproteins provides a "zinc-sparing response" and the expression of a set of alternative ribosomal proteins displaces small, Zn-containing peptides from the ribosome to provide zinc for the cell. In addition to the expression of high affinity metal ion uptake (acquisition) and the repression of non-essential metalloproteins (sparing), cells also express alternative isozymes for some essential functions that might otherwise be compromised (substitution). This proposal will focus on the characterization of these and related adaptive responses that enable cells to compete effectively even in severely metal-limited environments. PUBLIC HEALTH RELEVANCE: Project Narrative Metal ions are essential for life and function as cofactors for numerous enzymatic and electron transfer processes. This proposal seeks to understand how the model Gram positive bacterium Bacillus subtilis adapts to limitation for iron and zinc. These studies will provide significant insights into the adaptive processes which enable Gram positive pathogens (e.g. Staphylococcus aureus, streptococci, and enterococci) to survive in the metal-limited environments encountered in the host.