Overproduction of Magnetosomes by Genomic Amplification of Biosynthesis-Related Gene Clusters in a Magnetotactic Bacterium
Overproduction of Magnetosomes by Genomic Amplification of Biosynthesis-Related Gene Clusters in a Magnetotactic Bacterium
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DOI：
10.1128/aem.03860-15
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发表时间：
2016-05-01
影响因子：
4.4
通讯作者：
Schueler, Dirk
中科院分区：
文献类型：
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作者：
Lohsse, Anna;Kolinko, Isabel;Schueler, Dirk
趋磁细菌生物合成特定的细胞器，磁小体，这是一种磁性铁矿物的膜封闭晶体，以线性链排列。磁小体颗粒的数量和大小必须严格控制，以建立足够强大的传感器，以确保细胞在地球弱磁场中的有效排列，同时最大限度地减少过度磁小体生物合成所带来的代谢成本。除了它们的生物学功能之外，细菌磁小体已经获得了相当大的兴趣，因为它们为原核细胞器的形成提供了非常有用的模型，并且代表了具有特殊性质的生物磁性纳米颗粒。然而，这些难养细菌的培养困难和磁小体产量低阻碍了潜在的应用。在这项研究中，我们发现细胞内磁小体的大小和数量是由许多不同的Mam和Mms蛋白控制的。我们提出了一种通过转座进行单个和多个磁小体基因簇的染色体增殖，在α蛋白杆菌Magnetospirillum gryphiswaldense中过表达磁小体生物合成基因的策略。虽然mms6操纵子的逐步扩增导致形成越来越大的晶体（增加类似于35%），但所有主要磁小体操纵子（mamGFDC、mamAB、mms6和mamXY，总共包含29个基因）的复制产生了其中磁小体数目增加2.2倍的超量产生菌株。我们证明了mam和p2p簇的调节表达为控制磁小体的大小和数量提供了强有力的策略，从而为通过合成生物学方法高产量生产定制的磁性纳米颗粒奠定了基础。重要在我们的研究之前，磁小体的上限大小和数量是如何遗传调节的仍然是未知的，并且磁小体生物合成的过度生产尚未实现，这是由于在趋磁细菌中进行大规模基因组工程的困难。在这项研究中，我们建立和系统地探索了一种策略，磁小体生物合成基因的过表达的单个和多个磁小体基因簇的基因组扩增通过顺序的染色体插入转座。我们的研究结果还表明，磁小体蛋白的表达水平一起限制了细胞内磁小体的上限大小和数量。我们证明了磁小体基因簇的调谐过表达为精确控制磁小体的大小和数量提供了一个强有力的策略。
Magnetotactic bacteria biosynthesize specific organelles, the magnetosomes, which are membrane-enclosed crystals of a magnetic iron mineral that are aligned in a linear chain. The number and size of magnetosome particles have to be critically controlled to build a sensor sufficiently strong to ensure the efficient alignment of cells within Earth's weak magnetic field while at the same time minimizing the metabolic costs imposed by excessive magnetosome biosynthesis. Apart from their biological function, bacterial magnetosomes have gained considerable interest since they provide a highly useful model for prokaryotic organelle formation and represent biogenic magnetic nanoparticles with exceptional properties. However, potential applications have been hampered by the difficult cultivation of these fastidious bacteria and their poor yields of magnetosomes. In this study, we found that the size and number of magnetosomes within the cell are controlled by many different Mam and Mms proteins. We present a strategy for the overexpression of magnetosome biosynthesis genes in the alphaproteobacterium Magnetospirillum gryphiswaldense by chromosomal multiplication of individual and multiple magnetosome gene clusters via transposition. While stepwise amplification of the mms6 operon resulted in the formation of increasingly larger crystals (increase of similar to 35%), the duplication of all major magnetosome operons (mamGFDC, mamAB, mms6, and mamXY, comprising 29 genes in total) yielded an overproducing strain in which magnetosome numbers were 2.2-fold increased. We demonstrate that the tuned expression of the mam and mms clusters provides a powerful strategy for the control of magnetosome size and number, thereby setting the stage for high-yield production of tailored magnetic nanoparticles by synthetic biology approaches.IMPORTANCEBefore our study, it had remained unknown how the upper sizes and numbers of magnetosomes are genetically regulated, and overproduction of magnetosome biosynthesis had not been achieved, owing to the difficulties of large-scale genome engineering in the recalcitrant magnetotactic bacteria. In this study, we established and systematically explored a strategy for the overexpression of magnetosome biosynthesis genes by genomic amplification of single and multiple magnetosome gene clusters via sequential chromosomal insertion by transposition. Our findings also indicate that the expression levels of magnetosome proteins together limit the upper size and number of magnetosomes within the cell. We demonstrate that tuned overexpression of magnetosome gene clusters provides a powerful strategy for the precise control of magnetosome size and number.