Magnetosome chains are recruited to cellular division sites and split by asymmetric septation
Magnetosome chains are recruited to cellular division sites and split by asymmetric septation
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DOI：
10.1111/j.1365-2958.2011.07874.x
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发表时间：
2011-12-01
影响因子：
3.6
通讯作者：
Schueler, Dirk
中科院分区：
文献类型：
--
作者：
Katzmann, Emanuel;Mueller, Frank D.;Schueler, Dirk
趋磁细菌使用有序的膜封闭磁性晶体链（称为磁小体）沿沿着磁场线导航，磁小体已成为研究原核系统中细胞器生物发生的模型。为了在胞质分裂过程中忠实地分裂和分离，磁小体链必须正确定位，切割和分离以抵抗链内的静磁力。在这里，我们证明了趋磁细菌使用专门的机制来控制磁小体链的位置和分裂，从而在整个分裂周期中保持磁性方向。使用电子和延时显微镜同步细胞的磁小体gryphiswaldense，我们证实，磁小体链进行动态极到中细胞易位在胞质分裂。新生链招募分裂网站也在分裂抑制的细胞，但不是在mamK突变体，表明一个积极的机制依赖于肌动蛋白样细胞骨架磁小体丝。冷冻电子断层扫描显示，磁小体链和磁小体丝分裂成两半的不对称分隔和单向压痕，我们解释的一个特定的适应需要克服分离的子链之间的静磁相互作用。我们的研究表明，磁小体的分裂和分离与胞质分裂相协调，类似于细菌中其他细胞器和大分子复合物的分配机制。
Magnetotactic bacteria navigate along magnetic field lines using well-ordered chains of membrane-enclosed magnetic crystals, referred to as magnetosomes, which have emerged as model to investigate organelle biogenesis in prokaryotic systems. To become divided and segregated faithfully during cytokinesis, the magnetosome chain has to be properly positioned, cleaved and separated against intrachain magnetostatic forces. Here we demonstrate that magnetotactic bacteria use dedicated mechanisms to control the position and division of the magnetosome chain, thus maintaining magnetic orientation throughout divisional cycle. Using electron and time-lapse microscopy of synchronized cells of Magnetospirillum gryphiswaldense, we confirm that magnetosome chains undergo a dynamic pole-to-midcell translocation during cytokinesis. Nascent chains were recruited to division sites also in division-inhibited cells, but not in a mamK mutant, indicating an active mechanism depending upon the actin-like cytoskeletal magnetosome filament. Cryo-electron tomography revealed that both the magnetosome chain and the magnetosome filament are spilt into halves by asymmetric septation and unidirectional indentation, which we interpret in terms of a specific adaptation required to overcome the magnetostatic interactions between separating daughter chains. Our study demonstrates that magnetosome division and segregation is co-ordinated with cytokinesis and resembles partitioning mechanisms of other organelles and macromolecular complexes in bacteria.