Dynamic Remodeling of the Magnetosome Membrane Is Triggered by the Initiation of Biomineralization.
Dynamic Remodeling of the Magnetosome Membrane Is Triggered by the Initiation of Biomineralization.
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DOI：
10.1128/mbio.01898-15
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发表时间：
2016-02-16
期刊：
影响因子：
6.4
通讯作者：
Komeili A
中科院分区：
文献类型：
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作者：
Cornejo E;Subramanian P;Li Z;Jensen GJ;Komeili A
趋磁细菌产生膜结合细胞器链，指导磁性纳米颗粒的生物矿化。这些磁小体隔间是研究细菌细胞器的生物起源和亚细胞组织的模型。先前的研究表明，离散的基因产物以逐步的方式构建和组装磁小体。在这里，使用诱导系统，我们表明，磁小体形成的阶段是高度动态和相互关联的。在从头形成过程中，磁小体首先组织成不连续的链片段，随后由细菌肌动蛋白样蛋白MamK连接。我们还发现，磁小体膜的大小是不均匀的，可以生长在一个生物矿化依赖的方式。在没有生物矿化的情况下，磁小体膜在直径约50 nm处停滞。那些已经开始生物矿化的磁性颗粒随后膨胀到显著更大的尺寸并容纳成熟的磁性颗粒。我们推测，这种生物矿化依赖的膜生长检查点建立了适当的条件内的磁小体，以确保成功的成核和磁性颗粒的生长。趋磁细菌在称为磁小体的膜结合细胞器内制造磁性纳米颗粒;然而，目前还不清楚磁小体膜如何控制这种细菌细胞器内发生的生物矿化。我们将磁小体的形成在磁小体AMB-1的诱导控制下，并使用电子冷冻断层扫描捕捉磁小体在其近天然状态，因为它们形成从头。一个诱导系统提供了关键的证据，磁小体膜不断增长，除非他们没有适当地启动生物矿化。我们发现细菌细胞器的大小影响其生化功能，这是一个根本性的进步，影响了我们对细胞器形成的看法，并可以为未来旨在创造设计师磁性颗粒的尝试提供信息。
Magnetotactic bacteria produce chains of membrane-bound organelles that direct the biomineralization of magnetic nanoparticles. These magnetosome compartments are a model for studying the biogenesis and subcellular organization of bacterial organelles. Previous studies have suggested that discrete gene products build and assemble magnetosomes in a stepwise fashion. Here, using an inducible system, we show that the stages of magnetosome formation are highly dynamic and interconnected. During de novo formation, magnetosomes first organize into discontinuous chain fragments that are subsequently connected by the bacterial actin-like protein MamK. We also find that magnetosome membranes are not uniform in size and can grow in a biomineralization-dependent manner. In the absence of biomineralization, magnetosome membranes stall at a diameter of ~50 nm. Those that have initiated biomineralization then expand to significantly larger sizes and accommodate mature magnetic particles. We speculate that such a biomineralization-dependent checkpoint for membrane growth establishes the appropriate conditions within the magnetosome to ensure successful nucleation and growth of magnetic particles. Magnetotactic bacteria make magnetic nanoparticles inside membrane-bound organelles called magnetosomes; however, it is unclear how the magnetosome membrane controls the biomineralization that occurs within this bacterial organelle. We placed magnetosome formation under inducible control in Magnetospirillum magneticum AMB-1 and used electron cryo-tomography to capture magnetosomes in their near-native state as they form de novo. An inducible system provided the key evidence that magnetosome membranes grow continuously unless they have not properly initiated biomineralization. Our finding that the size of a bacterial organelle impacts its biochemical function is a fundamental advance that impacts our perception of organelle formation and can inform future attempts aimed at creating designer magnetic particles.